[Index]
Monthly Global Tropical Cyclone Summary September 2001
[Summaries and Track Data] [Prepared by Gary Padgett]
| Tropical
Cyclones
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Monthly Global Tropical Cyclone Summary September 2001 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
SEPTEMBER, 2001
(For general comments about the nature of these summaries, as well as
information on how to download the tabular cyclone track files, see
the Author's Note at the end of this summary.)
SPECIAL NOTE: Michael Bath, who lives near the northern coast of New
South Wales, has agreed to be my proofreader for the summaries. This
should help speed up the preparation time for the summaries a good bit.
A special thanks to Michael for agreeing to serve in this capacity.
***********************************************************************
SEPTEMBER HIGHLIGHTS
--> Atlantic produces four hurricanes--none make landfall as hurricanes
--> Northeast Pacific very active with one intense Category 4 hurricane
--> Northwest Pacific also very active with five typhoons
***********************************************************************
***** Feature of the Month for September *****
SOUTHERN HEMISPHERE TROPICAL CYCLONE NAMES
2001 - 2002 SEASON
TROPICAL CYCLONE NAMES for the AUSTRALIAN REGION
The Australian Bureau of Meteorology maintains three Tropical
Cyclone Warning Centres (TCWC): Perth, Western Australia; Darwin,
Northern Territory; and Brisbane, Queensland. Each centre is allotted
a separate list of tropical cyclone names for tropical cyclones forming
within its area of responsibility (AOR). In addition a TCWC located at
Port Moresby, Papua New Guinea (PNG)--a former Australian territory--
maintains a list of native names to assign to the very rare tropical
cyclones which form within its AOR.
The AORs of the respective centres are:
(1) Perth - 125E westward to 90E. Technically, Perth's AOR is south of
10S with Indonesia being responsible for waters north of 10S, but
I believe the plan is that any rare tropical cyclone which might
form north of 10S would be named by Perth.
(2) Darwin - 125E eastward to 138E and extending northward to the
equator. There is a little irregularity with the eastern border
in the Gulf of Carpentaria. The Darwin TCWC issues High Seas
Warnings for the entire Gulf of Carpentaria, but Brisbane issues
Tropical Cyclone Advices and names cyclones in the eastern portion
of the Gulf.
(3) Brisbane - 138E eastward to 160E and generally south of 10S. The
northern border with the Port Moresby AOR is somewhat irregular.
(4) Port Moresby, PNG - immediate vicinity of the island of New Guinea
and eastward to 160E generally north of 10S although the southern
border is somewhat irregular.
Names for the 2001-2002 season (** indicates name has already been
assigned):
Perth Darwin Brisbane Port Moresby
-----------------------------------------------------------------------
Alex ** Bonnie Bernie ** Epi
Bessi ** Craig Claudia ** Guba
Chris ** Debbie Des Ila
Dianne Evan Erica Kama
Errol Fay Fritz Matere
Fiona George Grace Rowe
Graham Helen Harvey Tako
Harriet Ira Ingrid Upia
Inigo Jasmine Jim
Jana Kim Kate
Ken Larry
Linda Monica
Monty Nelson
Nicky Odette
Oscar Pierre
TROPICAL CYCLONE NAMES for the SOUTHWEST INDIAN OCEAN
and the SOUTH PACIFIC OCEAN
The Tropical Cyclone Warning Centre (TCWC) at Nadi, Fiji, has
tropical cyclone warning responsibility for the South Pacific east of
160E and from the equator to 25S. The Meteorological Service of New
Zealand at Wellington has warning responsibility for waters south of
25S, but almost all tropical cyclones in this basin form north of 25S.
When a rare cyclone forms in the Wellington area of responsibility
(AOR), it usually will be assigned a name from the Fiji list (such as
was done for Tropical Cyclone Gita in February, 1999.)
Tropical cyclone warning responsibility for South Indian waters west
of 90E are shared by several TCWCs. The Regional Specialty
Meteorological Centre (RSMC) for the region is the office of Meteo
France on the island of La Reunion. However, following a long-standing
practice, the sub-regional centres at Mauritius and Madagascar share
the responsibility for actually naming tropical storms with Mauritius
naming systems east of 55E and Madagascar covering the area west of
55E. RSMC La Reunion issues warnings for the basin independently of
these sub-regional centres, but only advises regarding when or when not
to assign a name to a developing cyclone.
Names for the 2001-2002 season (** indicates name has already been
assigned):
Southwest Indian South Pacific
-----------------------------------------------------------------------
Andre ** Naly Trina ** Fili
Bako ** Orelie Vicky ** Gina
Cyprien ** Parina Waka ** Heta
Dina ** Quincy Yolande Ivy
Eddy ** Roger Zoe Judy
Francesca ** Solo Ami Kerry
Guillaume Teddy Beni Lola
Hary Usha Cilla Meena
Ikala Vero Dovi Nancy
Jery Wendy Eseta Olaf
Kesiny Xora
Lalita Yolande
Mirana Zaza
***********************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for September: 1 tropical depression
4 hurricanes
NOTE: Much of the information presented below was obtained from the
TPC/NHC discussion bulletins issued with every regular advisory. All
references to sustained winds imply a 1-min averaging period unless
otherwise noted. Some information was also obtained from the monthly
summary for September prepared by the Hurricane Specialists and
available on TPC/NHC's website.
In addition, I received a good deal of information from Peter Bowyer
of the Canadian Hurricane Centre on the effects several of the tropical
cyclones had on Newfoundland and the offshore fishing banks. Some of
the information was contained in reports prepared by Chris Fogarty of
the Newfoundland Weather Centre. A special thanks to Peter for sending
me these reports.
Atlantic Tropical Activity for September
----------------------------------------
In contrast to the month of August when no hurricanes formed in the
Atlantic basin, four tropical storms formed during September and all
reached hurricane intensity--two of these reached Category 3 on the
Saffir/Simpson scale. On the average the month of September produces
3.4 tropical storms with 2.4 reaching hurricane intensity and 1.2
attaining intense hurricane status. (These averages based on the
period 1950-2000.) Erin, the first hurricane of the 2001 season,
reached hurricane intensity on 8 September. This is the latest date
the first hurricane of the season has formed since 1984. Hurricanes
Erin and Felix both became Category 3 hurricanes, but fortunately both
remained well out in the Atlantic, although Erin brushed Bermuda.
Tropical Storm Gabrielle formed in the southeastern Gulf of Mexico
around mid-month and crossed the Florida Peninsula from west to east,
making landfall near Venice at just under hurricane intensity.
Gabrielle re-intensified in the Atlantic as it moved away from the
U. S. coast and reached hurricane intensity as it passed well west
of Bermuda. The final hurricane of the month, Humberto, formed in
a residual trough left over from Gabrielle south-southwest of Bermuda.
Humberto subsequently passed northward west of the island, eventually
turning northeastward across the North Atlantic shipping lanes.
A very interesting feature of the Atlantic tropical cyclones this
season has been the double peak in intensity all eight of the named
systems through the end of September have exhibited. A brief synopsis
follows:
(1) Allison - peaked at 50 kts off Texas coast, weakened over land,
then re-intensified to gale force as a subtropical cyclone over
southeastern Louisiana and southern Mississippi.
(2) Barry - reached an initial peak of 40 kts before weakening into a
tropical depression, then re-intensified to near hurricane force
as it moved inland in the Florida Panhandle. (Operationally,
Barry was maintained as a minimal tropical storm, but the weakening
to depression status will be reflected in the Best Track.)
(3) Chantal - actually a triple peak intensity of sorts. Upgraded to
a tropical storm east of the Windward Islands but weakened into an
open wave later the same day. Redeveloped in the central
Caribbean Sea and reached an intensity of 60 kts, weakened slightly
due to shear in the western Caribbean, then re-intensified to
60 kts just as it made landfall on the southern Yucatan Peninsula.
(NOTE: In a telephone conversation with Jack Beven, Jack indicated
that in the Best Track file Chantal will most likely not be
considered a tropical storm east of the Antilles.)
(4) Dean - developed suddenly just north of the Virgin Islands into a
50-kt tropical storm, but was sheared apart and dissipated the next
day. The remnant LOW then moved northward and interacted with an
old frontal trough, regaining tropical storm intensity north of
Bermuda and almost reaching hurricane intensity before moving over
colder SSTs in the North Atlantic.
(5) Erin - initially developed into a 50-kt tropical storm in the
tropical Atlantic east of the Lesser Antilles, then weakened into a
tropical wave due to hostile shear. A new center formed to the
north 24 hours later and ultimately developed into Hurricane Erin.
(6) Felix - became a tropical depression in the eastern Atlantic but
weakened into a tropical wave 24 hours later. Redeveloped a
couple of days later and eventually became Hurricane Felix. (Felix
was the only one of the eight which did not have a double peak in
intensity after becoming a named storm.)
(7) Gabrielle - formed in the southeastern Gulf of Mexico, made land-
fall near Venice, Florida, just shy of hurricane intensity, weak-
ened over land but re-intensified after moving into the Atlantic,
ultimately reaching hurricane force west of Bermuda.
(8) Humberto - reaching an initial peak intensity of 85 kts while
passing west of Bermuda, weakened to minimal hurricane intensity
a day later, then very surprisingly underwent a rejuvenation with
winds climbing to 90 kts north of the 40th parallel!
Interestingly, none of the seven tropical cyclones forming after
1 October displayed a double peak in intensity except for Hurricane
Karen, and its initial peak was reached as an extratropical storm
before undergoing an evolution into a subtropical and later tropical
cyclone.
In addition to the four hurricanes, the only other tropical cyclone
during September was a short-lived tropical depression in the western
Caribbean. A tropical wave was noted approaching the Windward Islands
on 15 September. The wave moved through the islands into the eastern
Caribbean on the 16th accompanied by showers, thunderstorms, and gusty
winds. The disturbance continued westward across the Caribbean during
the next few days with little sign of development. As it reached the
western Caribbean on the 19th, early morning visible satellite imagery
suggested that it had become better organized. Advisories were
initiated on Tropical Depression #9 at 2100 UTC. The circulation was
broad and there appeared to be two centers--one east of Costa Rica
and one about 100 nm east-southeast of Puerto Cabezas, Nicaragua.
The strongest and most persistent deep convection was associated with
the northernmost center, so that center was considered to be the
primary one. Upper-level outflow was very circular and quite
impressive.
The depression moved steadily westward and by 20/0000 UTC was moving
inland near Puerto Cabezas. Although the surface circulation began
to quickly weaken over the mountainous terrain, the cloud pattern
remained well-organized. The remnants of Tropical Depression #9
subsequently moved across Central America and emerged into the Eastern
Pacific where they eventually developed into Hurricane Juliette, which
became the second major hurricane of the season in that basin.
Hurricane Erin (TC-06)
1 - 17 September
-----------------------
A. Origins
----------
A vigorous tropical wave left the west African coast on 30 August,
passing south of the Cape Verde Islands the night of the 30th.
Environmental conditions were favorable and some of the numerical
models were suggesting that tropical cyclone development might occur
in a couple of days. The wave remained poorly organized on the 31st
but overnight the convective organization improved. TPC/NHC initiated
advisories on Tropical Depression #6 at 2100 UTC on 1 September with
the center located roughly 650 nm west-southwest of the Cape Verdes.
A drifting buoy west of the LLCC had reported a northwest wind of
15 kts and a pressure of 1008.7 mb. Deep convection had increased
markedly and this trend continued through the night. By early morning
of the 2nd Dvorak numbers were T3.0 from SAB and T2.5 from TAFB, so
the depression was upgraded to Tropical Storm Erin with 40-kt winds.
B. Track and Intensity History
------------------------------
Erin set out on a westward track, strengthening slightly to 45 kts
as the 2nd progressed. The storm remained poorly organized, even
though shear was weak and outflow good. Winds were upped to 50 kts
at 03/0900 UTC when the cyclone was centered about 950 nm east of the
island of Barbados. However, the upper and lower circulation centers
were still not vertically aligned. Visible pictures during the
morning of 3 September revealed an exposed LLCC southwest of the main
CDO feature. At 1000 UTC a drifting buoy about 60 nm west of the
center reported 31-kt winds. By 1100 UTC the buoy was reporting north
winds of only 20 kts with an attendant SLP of 1008.4 mb. The 1500 UTC
discussion noted that tropical storm-force winds were likely confined
to the northeast quadrant.
As Erin moved westward it moved closer to an upper-level LOW which
induced shear over the cyclone. Several bursts of convection were
noted, but the cold clouds had an amorphous shape. The MSW was reduced
to 40 kts at 2100 UTC. However, by early on 4 September the shear had
decreased and the storm appeared better organized. NHC raised the MSW
back to 45 kts at 0900 UTC based on a 0200 UTC buoy report of 41-kt
winds about 40 nm northeast of the center. Also, outflow had improved
and the convective pattern was more circular in appearance. The
abatement in the shear, however, was temporary. The first flight into
the storm by the Hurricane Hunters on the morning of 5 September found
a poorly-defined circulation with a minimum pressure of 1013 mb. A
peak flight-level wind of 49 kts was measured east of the center.
Tropical Storm Erin was downgraded to a tropical wave at 05/2100 UTC
about 250 nm northeast of Guadeloupe, having lost its circulation and
deep convection due to a hostile environment. The system appeared to
have several weak centers of vorticity along the wave axis.
On the morning of 6 September, a Tropical Weather Outlook issued by
NHC noted that thunderstorms had increased overnight and that a LLCC
might be forming on the southwestern side of the new patch of deep
convection. A reconnaissance flight was dispatched into the area
during the afternoon and found a poorly-defined LLCC with winds of
30-35 kts at flight level in rainbands. The cloud pattern was
gradually becoming better organized with an impressive curved band of
convection to the north. Advisories were re-initiated on Tropical
Depression Erin at 2100 UTC, locating the new center about 650 nm
southeast of Bermuda--well to the north of where the old one had
dissipated the day before. Visible satellite imagery on the morning
of the 7th indicated that the LLCC and outflow had improved since the
previous day. Erin was likely a tropical storm at 1500 UTC, but the
forecaster preferred to wait until the Hurricane Hunters investigated
the cyclone during the afternoon before upgrading. The reconnaissance
crew found a SLP of 1004 mb and flight-level winds of 46 kts northeast
of the center, so Erin was upgraded once more to tropical storm status
at 2100 UTC. Convection was not particularly deep, but the LLCC was
well-defined with good banding and fair outflow.
A shortwave trough passing to the north had weakened the steering
currents and Erin began a slow drift to the north-northwest. The CP
had dropped to 999 mb by 08/0600 UTC with 49-kt winds found at the
925-mb level northeast of the center. Visible pictures during the
morning of the 8th indicated a much better-organized storm than 24
hours previously with good banding and deep convection near the center.
Dvorak numbers had reached T3.5, so the MSW was upped to 45 kts at
1500 UTC. A strengthening ridge to the north was steering Erin on a
slow northwesterly track. Based on the official forecast track, a
hurricane watch was issued for Bermuda. During the afternoon visible
imagery revealed a well-defined cloud band wrapping around the center,
indicating that a banding eye was likely forming. A reconnaissance
flight found a pressure of 994 mb with flight-level winds of 76-80 kts,
so Erin was upgraded to a hurricane at 2100 UTC when located roughly
350 nm southeast of Bermuda. A flight into the hurricane during the
evening found winds of 84 kts and a CP of 992 mb, and concurrent
satellite intensity estimates were 77 kts, so the intensity was bumped
up to 75 kts at 09/0300 UTC. Erin was sporting an eye 35-40 nm in
diameter with good outflow, especially to the north of the center.
A reconnaissance flight around 0600 UTC on 9 September found a
flight-level wind of 101 kts at 700 mb with an attendant pressure of
982 mb, so the MSW was increased to 90 kts at 0900 UTC, making Erin a
Category 2 hurricane on the Saffir/Simpson scale. The eye continued
to become better defined, and the next flight into the storm at 1800
UTC found that Erin had deepened into a major Category 3 hurricane.
Peak winds at 700 mb were 118 kts while a GPS drop into the north-
eastern eyewall showed a spot surface wind of 111 kts with mean
boundary layer winds around 100 kts; the official MSW was set to
105 kts as a compromise. The CP had fallen to 968 mb--a little high
for 105 kts, but environmental pressures were also rather high. The
center of Hurricane Erin was located about 100 nm east of Bermuda at
the time it became the season's first major hurricane.
The 105-kt intensity was maintained for 24 hours. The cloud tops
warmed a bit during the night, but the eye became even better defined.
Erin continued moving to the north-northwest, and by 1500 UTC on the
10th was centered approximately 150 nm north of Bermuda, and was
displaying the classic signature of a major hurricane with a well-
defined eye 30 nm in diameter. A NOAA P3 research plane flew into
Erin during the afternoon, and data suggested that the winds had likely
weakened a bit to 100 kts or less. Wind profile data indicated that
Erin had formed concentric eyewalls. During the evening stepped-
frequency microwave radiometer data and GPS drops indicated that
surface winds had decreased to around 80 kts, although one drop
reported 89 kts at an altitude of 17 m. Dvorak intensity estimates,
however, were still 90 kts, so the MSW was lowered to 85 kts at 11/0300
UTC. By 0900 UTC on 11 September, Erin had reached the ridge axis
and was preparing to recurve to the northeast. The intensity had
dropped to 80 kts, where it remained for 18 hours.
By early on 12 September Erin had recurved and was moving in an
eastward direction. The intensity was reduced to 75 kts, but as the
hurricane was moving over a ribbon of warm water, the weakening process
was slow. Large swells from Erin reached the northeastern U. S. during
this period. On the 13th the storm turned more to the northeast,
although at a slow pace. The eye remained large and well-defined with
Erin still moving over 26 C SSTs. The MSW was lowered to 70 kts at
13/0600 UTC and remained pegged there for 24 hours. Late on the
13th the eye was still apparent in infrared imagery, but eyewall
convection had become asymmetric, perhaps due to the storm's
encountering cooler waters.
By early on 14 September Erin had accelerated to 17 kts. The eye
was still visible but the MSW was lowered to 65 kts. As the day
progressed Erin's eye disappeared and the convection became displaced
north of the center--signs that the storm was beginning extratropical
transition. Satellite intensity estimates remained at 65 kts however,
so the cyclone was maintained as a hurricane. Buoy 44625, located
northwest of the center, reported a pressure of 988.2 mb at 1800 UTC.
By 15/0300 UTC the remaining convection had become confined to the
northwest quadrant. TAFB was still reporting 65 kts, but SAB had
classified the storm as extratropical, so the final NHC advisory was
issued, downgrading Erin to a 60-kt storm that was rapidly becoming
extratropical. Erin at this time was located very near Cape Race,
Newfoundland, and the remnant extratropical storm continued moving
rapidly northeastward the next couple of days. The last reference
to the system in MPC's High Seas Forecasts was at 17/0000 UTC when
it was a 40-kt gale near 65N, 35W, still moving northeastward.
In summary, the peak intensity of Hurricane Erin (per TPC/NHC's
operational advisories) was 105 kts from 09/1800 UTC through 10/1800
UTC. The minimum pressure measured by the Hurricane Hunters was
968 mb at 09/1800 UTC. Gale-force winds extended out from the center
150 nm to the northeast and 100 nm elsewhere while hurricane-force
winds reached outward 40 nm in the eastern semicircle and 30 nm in
the western semicircle.
C. Meteorological Observations
------------------------------
In addition to the reconnaissance data and buoy reports incorporated
into the above section, I have received some information from Peter
Bowyer of the Canadian Hurricane Centre regarding observations made in
southeastern Canada and in offshore waters. The Laurentian Fan Buoy
(WMO 44141) reported wave heights to 9 m as Erin passed by early on
14 September. As the storm passed a few miles south of the Nickerson
Bank Buoy, seas built to 7 m with a maximum wave height of 14 m being
reported at 15/0000 UTC.
Rain began falling in Newfoundland late on the 13th from a quasi-
stationary frontal zone extending northeast of Erin. The heaviest
rain was concentrated along the southern coast of Newfoundland west
of the Burin Peninsula where more than 100 mm was recorded at Sagona
Island and Burgeo. A second wave of rain, associated with Erin's
cloud shield, brought amounts near 75 mm from Bonavista to the Burin
Peninsula. A few of the higher storm totals are:
Sagona Island - 131 mm
Burgeo - 102 mm
Bonavista - 78 mm
St. Lawrence - 66 mm
Lethbridge - 63 mm
No hurricane force winds were reported on land. Some exposed
coastal stations reported gusts of 58 kts in northwesterlies behind
Erin while the strongest winds in the easterlies ahead of the storm
were at Cape Race, where a peak gust of 52 kts was recorded at 2124
UTC on the 14th. Both Cape Race and Bonavista reported gusts to 58 kts
early on the 15th. St. John's and Grates Cove reported gusts to
45 kts and 49 kts, respectively, also early on the 15th.
D. Damage and Casualties
------------------------
No reports of any damage or casualties resulting from Hurricane Erin
have been received.
Hurricane Felix (TC-07)
7 - 19 September
------------------------
A. Origins
----------
A tropical wave left the African coast on 3 September and marched
westward across the tropical Atlantic. This wave never developed into
a tropical cyclone, but did influence and interact with the following
wave which eventually became Felix. The cyclone tracks file for
September contains a track of this leading disturbance which was sent
to the author by Roger Edson. No advisories were issued by NHC on this
system--it was treated as a tropical wave--although some of the
Tropical Weather Discussions indicated that a broad circulation
was associated with the wave. Roger estimated that the LOW was
accompanied by winds up to 30 kts, which is plausible--many tropical
waves are accompanied by winds of 30 kts or stronger without forming a
well-defined low-level circulation.
The next tropical wave to emanate out of Africa entered the Atlantic
on 5 September. A 1009-mb LOW was noted on the 6th as the well-
organized disturbance passed south of the Cape Verdes. By the after-
noon of the 7th, the system had become better organized with banding
features and good outflow and was classified as a tropical depression
at 07/2100 UTC when located about 350 nm west of the Cape Verdes.
During the night of 7 September Tropical Depression #7 displayed a band
of strong convection, but no deep convection was located near the
center. By the morning of the 8th the depression consisted of a
broad circulation with only a few bands of convection, and by afternoon
no evidence of a LLCC could be seen in satellite imagery, so the system
was downgraded to a tropical wave and advisories discontinued.
In the meantime, the tropical LOW preceding TD-07 had become quasi-
stationary in mid-ocean, and by the morning of 9 September the remnants
of the depression were combining with the leading wave to produce a
broad low-pressure area about 1100 nm east of the Lesser Antilles.
Advisories on TD-07 were re-initiated at 0900 UTC on 10 September with
the center located about 525 nm west of the earlier final position at
08/1800 UTC, or about 1000 nm east of Martinique. Deep convection had
persisted near the LLCC while outflow had become more pronounced.
Also, some nearby buoys had reported pressures around 1008 mb. Visible
pictures on the 10th brought a complication, however. Two distinct
LLCCs were evident, one consistent with the previous west-northwestward
motion while a weaker circulation to the southeast was associated with
the weaker tropical wave that had preceded the depression. The deepest
convection was concentrated east of the northern vortex, which was
considered to be the primary center.
There was some question during the night of the 10th as to whether
or not the system was maintaining a closed circulation, but depression
status was maintained pending the availability of visible images the
next morning. Organization improved, however, and at 11/0900 UTC all
three satellite estimates were near tropical storm strength. By 1500
UTC the LLCC had become better defined under deep convection and the
outflow had gradually improved, so the depression was upgraded to
Tropical Storm Felix at this time. The newly-christened tropical
storm was located about 800 nm east-northeast of Guadeloupe and was
moving north-northwestward around the periphery of a subtropical ridge.
B. Track and Intensity History
------------------------------
For the first 24 hours of its life as a tropical storm, Felix
remained at minimal tropical storm intensity. Convection, while deep,
was displaced to the northeast of the LLCC. Morning visible images
on 12 September indicated that the cyclone had become better organized
with the center embedded in deep convection and an eye-like feature
trying to develop. The MSW was increased to 55 kts at 1500 UTC and to
60 kts at 2100 UTC. Felix was upgraded to a 65-kt hurricane at
13/0300 UTC based on Dvorak estimates, partially-contaminated QuikScat
data, and a doughnut-shaped feature in SSM/I imagery. The storm by
this time was moving north, or slightly east of due north, and
strengthened quickly after reaching hurricane intensity. The advisory
issued at 13/1500 UTC noted that Felix had developed an eye embedded
within the CDO with plenty of banding and fair outflow. Satellite
intensity estimates from TAFB and SAB had reached T5.0, so the MSW
was increased to 90 kts. By 1800 UTC the satellite presentation of the
storm had continued to improve--the eye was distinct and surrounded by
very deep convection with plenty of curved bands. TAFB had increased
their Dvorak estimate to T5.5, so the MSW was upped to 100 kts, making
Felix the second Category 3 hurricane of the season. The storm at this
time was centered roughly 1200 nm southwest of the Azores, moving
northward.
Felix remained at its peak intensity of 100 kts for 18 hours, then
began to slowly weaken. By 1500 UTC on the 14th the eye had
disappeared in infrared imagery and was not well-defined in visible
pictures. Also, water vapor imagery indicated that some southwesterly
shear was impinging on the cyclone. The MSW was reduced to 95 kts
at 1500 UTC and to 90 kts at 2100 UTC. Felix was by this time moving
northeastward at 13 kts, and this motion had become east-northeasterly
by 15/0300 UTC. By the morning of 15 September the hurricane was
moving eastward and continuing to show signs of weakening. Visible
imagery suggested that mid- to upper-level winds were undercutting the
impressive cirrus outflow and inducing mid-level shear. The MSW was
left at 90 kts, although the discussion noted that this might be on
the high side. Around 1500 UTC a drifting buoy (41644) reported a
pressure of 975.8 mb in the northwest quadrant of the eye. Although
deep convection persisted near the LLCC, the areal coverage had shrunk
and, based in part on the buoy report, the MSW was lowered to 85 kts
at 2100 UTC. At 16/0300 UTC satellite intensity estimates from TAFB,
SAB and AFWA were 90 kts, 77 kts, and 65 kts, respectively, and the
eye had reappeared in METEOSAT-7 infrared imagery, so the intensity
was left at 85 kts.
On the 16th the cloud pattern associated with Felix became more
ragged with cloud tops warming and convection eroding over the south-
western semicircle--an upper-level trough appeared to be impinging
on the western side of the tropical cyclone. The MSW was lowered to
80 kts at 0900 UTC. About this time, drifting buoy 44765 reported a
SLP of 981.4 mb from a position about 60 nm northeast of the center.
The NHC discussion noted that central convection had decreased, but
that the eye had expanded to a diameter of 80 nm. There were
indications during the afternoon that the shear over Felix might be
lessening--there was a burst of deep convection noted in the north-
east quadrant. Drifting buoy 44765 was in the eye of Felix for most
of the morning and reported pressures ranging from 973.8 mb at 1100
UTC to 976 mb at 1500 UTC. The intensity was reduced to 75 kts at
2100 UTC and to 65 kts at 17/0300 UTC. Satellite intensity estimates
at this time were below hurricane force, but the earlier buoy data had
suggested that Dvorak estimates were a little low.
The storm's eastward motion had slowed to 8 kts or less by the
morning of 17 September as a mid-latitude trough had bypassed the area.
At 1500 UTC Felix was located about 250 nm south of the northwestern-
most Azores and was drifting to the southeast. Northwesterly shear had
displaced the convection to the southeast of the LLCC and the cyclone
was downgraded to a 60-kt tropical storm. SSTs in the area were about
24-25 C. Felix continued to slowly weaken as it remained quasi-
stationary or drifted slowly southward. Winds were down to 45 kts by
0300 UTC and continued to drop as the day progressed. By 0900 UTC
little if any deep convection remained as the storm drifted south-
southwestward, retracing its path over waters that had been cooled by
upwelling. Felix was being steered by flow on the eastern side of
a mid-level subtropical ridge. No deep convection was observed at
1500 UTC and the MSW was reduced to 35 kts. Drifting buoy 44765, which
had passed through the eye of Felix two days earlier, again encountered
the storm and reported a pressure of 1001.2 mb. Felix was downgraded
to a tropical depression at 2100 UTC, based on nearby ship reports of
25 kts. As the 19th began Felix consisted of a broad but rather well-
defined circulation devoid of any deep convection. A QuikScat pass
indicated maximum winds of 25 kts, and ship KAKF confirmed these winds
at a location well south of the center. Since models indicated no
chance of regeneration, NHC issued the final advisory on the former
Category 3 hurricane at 0300 UTC on 19 September with the remnant
LOW drifting slowly southward, well south of the Azores.
Hurricane Felix was at its estimated peak intensity of 100 kts from
1800 UTC on 13 September through 1200 UTC on the 14th with the central
pressure estimated at 965 mb during this period. At its peak Felix was
a large, severe hurricane. Gales covered an area between 300 and
400 nm in diameter and hurricane-force winds reached outward from the
center 30-40 nm in all directions.
C. Meteorological Observations
------------------------------
No reconnaissance missions were flown into Hurricane Felix. The
only surface reports available to the author were the buoy and ship
observations mentioned in the preceding section.
D. Damage and Casualties
------------------------
No damage or casualties are known to have resulted from Hurricane
Felix.
Hurricane Gabrielle (TC-08)
11 - 21 September
----------------------------
A. Origins
----------
A Tropical Weather Outlook issued by TPC/NHC on the afternoon of
8 September noted that disorganized cloudiness and thunderstorms
extended from the eastern Gulf of Mexico across the Florida Peninsula
into the northern Bahamas and adjacent Atlantic waters. This area of
disturbed weather was associated with a weak trough of low pressure.
The trough and unsettled weather persisted in the area for the next
few days, and on the morning of 11 September surface data revealed the
existence of a definite closed circulation over the southeastern Gulf
of Mexico. The deep convection did not show much curvature, but was
near enough to the LLCC to warrant classifying the system as a tropical
depression. The first advisory on TD-08 was issued at 2100 UTC with
the center located about 125 nm west-northwest of Key West, Florida.
The maximum winds were estimated at 25 kts, and with northerly shear
over the area and an upper-level vortmax moving south-southeasterly
toward the depression, strengthening was forecast to be slow.
By the early morning of the 12th the depression was a little better
organized. Buoy 42003 in the eastern Gulf reported a pressure below
1009 mb with a 24-hour drop of 4 mb. Deep convection remained to the
south of the broad and ill-defined center, but convective banding had
increased in the eastern semicircle across southern Florida. As the
day wore on an upper-level shortwave trough near the north-central
Gulf Coast modified the upper flow over the system, resulting in a
decrease in the shear. Satellite imagery revealed increasing
organization of the depression and buoy data indicated pressures were
continuing to fall, so the MSW was bumped up to 30 kts at 2100 UTC.
A reconnaissance plane visited the area during the evening and found
a very broad circulation with convection not very well organized near
the center, but rather oriented in a linear band extending from the
northern Yucatan coast to the southwest Florida coast.
Deep convection began to persist near the center on the morning of
13 September, and ship WPKD, located about 70 nm southeast of the
center, reported 32-kt sustained winds at 0600 UTC with a pressure of
1006 mb. Outflow was good in the southeastern semicircle but
restricted to the northwest due to upper-level shear. Around 1200
UTC ships DCUW and WCZ5238 reported winds of 35 and 40 kts,
respectively, and both TAFB and SAB had assigned a T2.5 Dvorak rating,
so the depression was upgraded to Tropical Storm Gabrielle with 40-kt
winds at 1500 UTC, located about 200 nm west-northwest of Key West.
The storm was still experiencing some shear--the center was partially-
exposed on the western edge of the deep convection.
B. Track and Intensity History
------------------------------
A reconnaissance flight during the afternoon found the center well
northeast of the previous position. It was not clear whether the
center had reformed or if the storm had been moving northeastward.
WSR-88D animation suggested the latter, so warnings were ordered up
for portions of the Florida coast. Gabrielle was located in a
shearing environment due to an upper-level trough over the eastern
Gulf of Mexico. However, the SHIPS model indicated that the storm
could become a hurricane before moving inland. The reconnaissance
flight at 14/0000 UTC found a pressure of 996 mb and flight-level winds
of 52 kts. The system was somewhat sheared with bursts of deep
convection forming east of the center. Heavy rainbands from Gabrielle
were spreading onshore over the southern Florida Peninsula and the
Keys. During the night the center of Gabrielle appeared to keep
reforming to the northeast under the convection. The reconnaissance
plane at 0600 UTC found a central pressure of 992 mb but encountered
winds of 70-75 kts at flight level near the Florida coast. The storm
at that time was moving northeastward at 9 kts.
The center of Gabrielle reached the southwestern Florida coast near
Venice around 1200 UTC on 14 September. The storm almost reached
hurricane intensity just before making landfall. Reconnaissance data
indicated that the pressure fell to 980 mb, and 700-mb winds as high
as 81 kts were measured at flight level. These, however, were near the
Venice C-MAN station, which at the time was reporting gusts to only
40 kts. It appears that the higher winds at flight-level were not
mixing down to the surface. Gabrielle spent the next 24 hours crossing
the Florida Peninsula, emerging into the Atlantic just northeast of
Cape Canaveral by around 1200 UTC on the 15th. The convection
decreased markedly after the storm made landfall with the strongest
remaining convection found in bands well-removed from the center to the
north and east. The MSW was maintained at 40 kts during Gabrielle's
overland trek, being supported by synoptic observations of 35-40 kts
near the Florida East Coast, particularly the St. Augustine C-MAN
station.
While over Florida Gabrielle began to take on the appearance of an
occluded frontal LOW more so than a tropical cyclone. The circulation
was large with a non-symmetrical wind field and devoid of any deep
convection near the center. The fact that the storm maintained a CP
less than 999 mb and winds of 40 kts while over land suggests that its
nature was not purely tropical. By 15/1500 UTC the center had moved
offshore into the Atlantic near Cape Canaveral. The NHC discussion
noted that it resembled a subtropical cyclone with the strongest winds
and convection removed from the center and an upper-level cyclone
superimposed over the surface center. A reconnaissance flight found
winds near 60 kts in the southeast and northwest quadrants with a CP
of 998 mb, so the MSW remained at 40 kts. Two ship reports of 43 and
44 kts at 1800 UTC led to the intensity being raised slightly to 45 kts
at 2100 UTC. Convection had moved a little closer to the center, but
Gabrielle still had a "frontal" look about it. SAB had classified
the system as extratropical, and TAFB was calling it a subtropical
storm. The cyclone was moving northeastward roughly parallel to the
southeastern U. S. coast and by 2100 UTC had accelerated to 13 kts.
The intensity was increased to 50 kts at 16/0300 UTC based on ship
reports of 50-kt winds in the northwest quadrant near the coast and
supported by reconnaissance data and GOES cloud drift winds which
indicated winds to 50 kts in other quadrants. Six hours later it
appeared that Gabrielle was about to become extratropical--a
reconnaissance mission reported that the center had become more
elongated with little or no core temperature rise at 850 mb. However,
the storm was still moving over warm waters and a slight increase in
convection near the center was noted. By 1500 UTC reconnaissance
reports and satellite imagery indicated that Gabrielle had become
better organized and had strengthened some. At 1140 UTC a pressure of
995 mb was measured and at 1328 UTC a plane found winds of 67 kts
northwest of the center, so the MSW was increased to 55 kts. The
temperature of the core had also warmed and satellite imagery indicated
increasing outflow in the northwest semicircle, suggesting that
Gabrielle was still a warm-core tropical cyclone as it sped northeast-
ward at 17 kts.
During the 16th the storm continued to develop deep convection on
the northern side of the ragged, exposed LLCC. Satellite intensity
estimates ranged from 35 kts from SAB to 55 kts from KGWC. At 0000
UTC on 17 September a GPS drop made by a NOAA research aircraft
reported winds of 68 kts near the center just above the surface, so
Gabrielle was upgraded to a 65-kt hurricane at 17/0300 UTC when
centered approximately 325 nm west of Bermuda. Even so, the system
still appeared to be sheared and asymmetric with the deep convection
to the north and east of the center. A dry slot wrapping around into
the southern semicircle produced a comma-cloud signature more typical
of subtropical storms than tropical cyclones. A reconnaissance flight
into Gabrielle around 1200 UTC measured winds to 85 kts at 1500 m along
with a pressure of 983 mb, so the MSW was bumped up to 70 kts in the
1500 UTC advisory.
By afternoon of the 17th Gabrielle was an impressive system in
satellite imagery despite the southwesterly shear affecting the storm.
Visible pictures indicated that a banding eye might be trying to form
as moderate convection had wrapped 3/4 of the way around the LLCC.
Also, the storm had good outflow to the north. However, at 18/0300 UTC
Gabrielle was downgraded to a 55-kt tropical storm. The upper-level
center was being displaced to the northeast of the LLCC by the south-
westerly shear. By 0900 UTC some deep convection had redeveloped just
north of the LLCC, so the intensity was maintained at 55 kts. However,
Gabrielle was well northeast of Bermuda at this time and beginning to
move over progressively cooler SSTs. Six hours later some deep
convection still persisted near the center, but the cloud pattern was
beginning to look more like an evolving extratropical low-pressure
system. The MSW of 55 kts in the 1500 UTC advisory was based on
tropical and extratropical satellite intensity estimates of 50 and
55 kts from TAFB and KGWC, respectively.
Deep convection continued to persist near Gabrielle's center through
the afternoon, but the appearance of the storm was more that of an
extratropical LOW. The MSW was increased to 60 kts at 2100 UTC based
on a report from ship WMLH, located about 90 nm northwest of the
center. Observations from the ship in conjunction with AMSU data
indicated that Gabrielle was still a warm-core system. NHC issued
their final advisory on Gabrielle at 19/0300 UTC with the storm
centered roughly 375 nm southwest of Cape Race, Newfoundland. A
recent QuikScat pass had indicated windspeeds near 60 kts, and earlier
a buoy had reported a pressure of 977.6 mb, but all cloud tops were
warmer than -50 C and there was no deep convection anywhere near the
LLCC, so Gabrielle was declared extratropical. At 1200 UTC on the 19th
the center of Post-Tropical Storm Gabrielle (the term used by the
Canadian Hurricane Centre) passed about 50 nm south-southeast of Cape
Race. The last reference to the system in MPC's High Seas Forecasts
placed the center near 59N, 31W, at 1800 UTC on 21 September, still
generating 50-kt winds.
Hurricane Gabrielle's peak intensity of 70 kts was attained at
17/1200 UTC and was maintained for twelve hours with an attendant
minimum CP of 983 mb. However, in the Gulf of Mexico phase of
Gabrielle, a reconnaissance plane measured a pressure of 980 mb at
14/1009 UTC, shortly before the tropical storm made landfall near
Venice, Florida. At the time of Gabrielle's peak intensity on the
17th, gales covered an area about 450 nm in diameter with the radius
of hurricane-force winds 25 nm in all directions. Shortly before
the storm made landfall in Florida, gales extended outward from the
center 125 nm to the northeast and 100 nm to the southeast.
C. Meteorological Observations
-------------------------------
As Tropical Storm Gabrielle approached the west coast of Florida
during the early morning of 14 September, Dry Tortugas reported winds
of 38 kts, gusting to 44 kts. Around mid-morning on the 14th the
AWS at Venice reported sustained winds to 50 kts with a peak gust of
63 kts. During the afternoon, St. Petersburg on the west coast and
St. Augustine on the Atlantic coast both reported gusts to 47 kts.
The St. Augustine AWS (elevation 16.5 m) reported sustained winds of
48 kts at 14/2200 UTC and 41 kts at 15/0100 UTC while Gabrielle's
center was over the peninsula. At 15/1800 UTC, ships DHER and OZQP2
reported sustained winds of 44 and 43 kts, respectively, while north-
west of the center. According to the NHC monthly summary for
September, rains in excess of 250 mm fell over portions of west-central
Florida and a storm surge of 1.5 m above normal affected the west coast
of the peninsula.
Bermuda reported wind gusts to 42 kts early on 17 September as
Gabrielle passed slightly more than 300 nm west of the island. The
storm had just been upgraded to a hurricane at that time. At 1800 UTC
on 18 September, when Gabrielle was southwest of Newfoundland, ship
WMLH, located about 90 nm northwest of the center, reported a pressure
of 984.5 mb with the air temperature 23.9 C and the dew point 22.2 C.
This observation, in conjunction with AMSU data, helped to establish
that Gabrielle was still a warm-cored system. Gabrielle's center
passed over or very near the Laurentian Fan Buoy (44141) just before
midnight on 19 September. Wave heights exceeded 9 m and the reported
SLP was 977.6 mb and falling. The Nickerson Bank Buoy (44251),
located about 80 nm northwest of Gabrielle, reported seas of 5 m.
In Newfoundland light rain began falling on the 18th over the
southern Avalon and Burin Peninsulas, well north of the storm's center.
The rain became heavier on the 19th, and between 0600 UTC and 1200 UTC
extremely heavy rain fell across the eastern Avalon Peninsula as
Gabrielle approached to within around 70 nm due south of Cape Race.
Much of the rain was due to embedded thunderstorms in the circulation
around Gabrielle. Cape Race recorded 48 mm in one hour between 0900
and 1000 UTC, and St. John's West measured 27 mm between 0600 and 0700
UTC. Some storm totals include:
Cape Race - 162 mm
St. John's West - 127 mm
St. John's Airport - 119 mm
Rainfall amounts west of the Avalon Peninsula were less than 35 mm.
Strong northerly winds were experienced over eastern sections of
Newfoundland with gusts to 54 kts or higher recorded on all three
peninsulas: Avalon, Bonavista, and Burin. Some of the peak winds
reported were:
Cape Race - 70 kts at 19/1257 UTC (maximum sustained 57 kts at
1200 UTC)
St. John's West - 48 kts at 19/1404 UTC
St. John's Airport - 47 kts at 19/1114 UTC
Grates Cove - 59 kts at 19/1816 UTC
Bonavista - 56 kts at 19/1900 UTC
Gander - 34 kts at 19/1600 UTC
Sagona Island - 54 kts at 19/1247 UTC
St. Lawrence - 56 kts at 19/1227 UTC
D. Damage and Casualties
------------------------
The heavy rains of Gabrielle led to major river flooding in west-
central Florida and on the lower St. Johns River. There was also
wind damage to roofs, mobile homes and trees. Total damage was
estimated at $230 million. A drowning death along the Alabama coast
was attributed to Gabrielle.
In Newfoundland extensive damage due to flooding occurred in St.
John's. Numerous basements were flooded and some streets were under-
mined. Local brooks and lakes swelled beyond capacity, inundating
parks and backyards. (No dollar amount of this damage was available.)
Hurricane Humberto (TC-10)
21 - 28 September
---------------------------
A. Storm Origins
----------------
After Tropical Storm Gabrielle had crossed Florida and moved on to
the northeast and strengthened as a sort of quasi-subtropical storm,
a residual trough, somewhat resembling a front, continued advancing
southeastward, reaching the general area between Puerto Rico and
Bermuda by 19 September. On that date a Tropical Weather Outlook
issued by NHC at 1530 UTC noted that a weak LOW accompanied by some
scattered convection was located about 475 nm northeast of Puerto
Rico. Afternoon satellite pictures indicated a circulation might be
forming, although environmental pressures were quite high. By midday
on the 20th convection was better organized around a well-defined
surface LOW about 350 nm northeast of Puerto Rico.
The LOW gradually became better organized through the night, and
advisories were initiated on Tropical Depression #10 at 1500 UTC on
21 September. The system had moved west-northwestward to a position
roughly 450 nm south of Bermuda by this time. Both TAFB and SAB were
estimating winds at 25 kts and deep convection was developing near the
center. The depression had a very impressive satellite signature with
plenty of banding, convection and cirrus outflow, but a reconnaissance
flight during the afternoon did not find a well-enough defined LLCC to
make a formal fix. Wind observations, however, did show a weak
surface circulation about 40 nm west-southwest of the upper-level
circulation center. An upper-level LOW to the southwest of TD-10 was
still inducing some shear over the system.
At 22/0000 UTC the intensity estimates from TAFB and SAB were both
35 kts, but ship KAKF, located near the depression's center, reported
winds of only 22 kts with a pressure of 1011.8 mb. By 0600 UTC, SAB's
estimate had reached 45 kts, and the system displayed a nicely curved
convective band in the eastern semicircle. However, multispectral
infrared imagery showed some exposed low-level cloud lines west of the
main convection. The 1200 UTC Dvorak estimates from all three agencies
were T3.0 (45 kts), and the cloud pattern was well-organized with
curved bands and fair outflow, but since on the previous day the system
was not as intense as satellite estimates had suggested, the forecaster
chose to maintain depression status pending the next reconnaissance
mission. The winds, however, were increased to 30 kts.
An early afternoon reconnaissance flight into the cyclone found a
fairly strong tropical storm with flight-level winds of 57 kts in the
west quadrant and a central pressure of 998 mb. A special Tropical
Update at 1830 UTC upgraded the depression to Tropical Storm Humberto,
located about 250 nm south-southwest of Bermuda and moving north-
westward at 10 kts. The initial intensity was set at 50 kts, and the
2100 UTC discussion noted that Humberto had a well-defined, tightly-
wound surface center. The storm was forecast to gradually turn to
the north around the periphery of the subtropical ridge to the east.
B. Track and Intensity History
------------------------------
By 0300 UTC on 23 September a CDO feature had developed, although
the MSW remained at 50 kts. A drifting buoy about 40 nm northwest of
the center had reported winds of 25 kts and a SLP of 1011.9 mb at
23/0000 UTC, indicating that Humberto was a rather small tropical
cyclone. The 0600 UTC reconnaissance flight found a pressure of
994 mb with 65-kt winds at 450 m both east and west of the developing
25-nm diameter eye. Convection had consolidated near the center and
outflow was good, so the intensity was upped to 55 kts. By mid-morning
on the 23rd Humberto displayed a cold symmetric CDO with good banding
north and east of the center, and an 1100 UTC SSM/I pass revealed a
doughnut-like eye feature. Estimates from TAFB and SAB had reached
65 kts, but the MSW was increased to only 60 kts since another plane
was due to reconnoiter the storm at 1800 UTC.
The reconnaissance flight at midday on the 23rd found a central
pressure of 984 mb and peak flight-level winds of 86 kts at the 700-mb
level northeast of the center, but a concurrent GPS drop near the eye-
wall measured only 56 kts at the surface. However, the mean boundary
layer windspeed was 79 kts, so the MSW was increased to 70 kts, making
Humberto the fourth hurricane of the season and also for the month of
September. Humberto was then centered approximately 125 nm west-
southwest of Bermuda, moving northward at 9 kts. Observations during
the evening from a multi-aircraft mission indicated that Humberto
had strengthened further. Eyewall dropsonde data from a NOAA research
airplane showed winds of 87 kts at the surface in the northeast
quadrant. Stepped-frequency microwave radiometer data also indicated
similar winds, so the MSW was increased to 85 kts at 24/0300 UTC,
making Humberto a Category 2 hurricane on the Saffir/Simpson scale.
The minimum pressure was 983 mb--a little high for 85 kts--but the
cyclone was embedded in a higher-than-normal sea-level pressure
environment.
Humberto's tenure as a Category 2 hurricane, however, was quite
brief. The reconnaissance plane at 0600 UTC found that the pressure
had risen to 989 mb, and the highest flight-level wind encountered
was 68 kts. Satellite imagery suggested some southwesterly shear
impacting the hurricane. The MSW was lowered to 80 kts, and was
further reduced by 5 kts on each subsequent advisory until Humberto
was a minimal 65-kt hurricane at 25/0300 UTC. Oddly, during the
morning of the 24th, Objective Dvorak numbers were slightly higher
than during the night. Cloud tops warmed significantly during the
day, and another multi-aircraft mission into the storm during the
evening indicated that Humberto had weakened into a minimal hurricane.
GPS drops measured surface winds around 62-64 kts and radar
observations indicated that the eyewall was open over most of the
southern semicircle. The weakening trend halted, however, and
throughout the 25th Humberto held on to hurricane intensity, displaying
an intermittent eye-like feature surrounded by deep convection. The
hurricane had recurved and was moving northeastward in the general
direction of Newfoundland.
Weakening and eventual extratropical transition were forecast, but
Humberto had one more trick up its sleeve. The NHC discussion at
0900 UTC on 26 September noted that an eye surrounded by deep
convection had persisted throughout the night, and with TAFB rendering
a Dvorak number of T4.5 (77 kts), the MSW was increased to 70 kts.
This improvement in Humberto's appearance coincided with a jog to the
north, probably in response to ridging near the cyclone downstream of
a large cutoff LOW over the Great Lakes. By 1500 UTC the 15-nm eye
had become better defined and cloud tops had cooled even more.
Dvorak numbers from both TAFB and SAB had reached T5.0, so Humberto's
winds were bumped up to 90 kts, making the storm once more a
Category 2 hurricane. The hurricane at this time was north of the
41st parallel about 300 nm southeast of Halifax, Nova Scotia. This
strengthening at such a northerly latitude was most unusual. Humberto
was located over SSTs of 25-26 C just south of a sharp SST gradient,
and a building upper-level ridge near and north of the storm had
apparently sheltered it from stronger westerlies.
However, like its first flirtation with Category 2 intensity,
Humberto was not able to maintain the 90-kt intensity for very long.
By afternoon the eye was becoming indistinct and the MSW was lowered
to 80 kts at 2100 UTC. The convective pattern was becoming asymmetric
with most of the cold clouds shifting to the northeast semicircle.
Humberto was likely feeling the effects of cooler SSTs and stronger
westerly flow, its forward speed having increased to 13 kts. The
Canadian Laurentian Fan Buoy (44141) reported a pressure of 990 mb
at 2100 UTC, and a SSM/I overpass at 2310 UTC showed a partial eye-
wall to the north. Although Dvorak intensity estimates remained at
90 kts, Humberto's organization was decreasing and the intensity was
reduced to 65 kts at 27/0300 UTC. Based on buoy reports, SSTs along
and near the forecast track of Humberto were ranging from 15-20 C.
On the 27th Humberto's track took an almost due eastward turn.
The storm was downgraded to a 60-kt tropical storm at 0900 UTC. The
convection was showing less banding and was becoming amorphous as
the cyclone accelerated eastward. Satellite intensity estimates were
still at hurricane intensity, but given the stabilizing cool SSTs, it
was deemed unlikely that any hurricane-force winds were making it down
to the surface. During the morning westerly flow aloft increased, and
by 1500 UTC Humberto was sailing eastward along a sharp SST gradient
at 28 kts. During the afternoon the cloud pattern deteriorated with
the convective cloud mass becoming elongated and distorted and removed
from the LLCC. NHC issued the final tropical advisory on Humberto
at 2100 UTC with the storm located about 500 nm east-southeast of Cape
Race and racing slightly south of due east at 27 kts. The storm was
rapidly becoming extratropical and was forecast to be absorbed into
a very large cyclonic circulation over the North Atlantic during the
next day or two.
Hurricane Humberto reached its first peak in intensity at 0300 UTC
on 24 September when the MSW and central pressure, based upon data
from a reconnaissance flight, were 85 kts and 983 mb, respectively.
Hurricane-force winds extended out 25 nm northeast and southeast of
the center and 15 nm elsewhere. Gales reached outward 90 nm in the
eastern semicircle and 35 nm in the western semicircle. Humberto's
primary peak occurred after the surprise re-intensification on the
morning of 26 September, but the 90-kt MSW and 970-mb central pressure
were only estimates based on satellite imagery. At the time of this
second peak in intensity, winds to hurricane force extended outward
30 nm from the center in all directions while 34-kt winds reached out
60 nm in the northern quadrants and 120 nm to the southeast.
C. Meteorological Observations
------------------------------
I have received no synoptic reports associated with Humberto other
than the buoy observation referenced in the above section.
D. Damage and Casualties
------------------------
No reports of damage or casualties resulting from Hurricane Humberto
have been received. According to information from Peter Boywer of the
Canadian Hurricane Centre, Humberto was exclusively a marine event and
had no impact on inland areas in the Canadian Maritimes. Like its
predecessors, however, Humberto did pass over the Laurentian Fan and
Southwestern Grand Banks marine areas, being the fourth tropical
cyclone in less than a month to bring storm or hurricane-force winds
to those areas.
ADDENDUM TO AUGUST SUMMARY
Impact of Tropical Storm Dean in Southeastern Canada
----------------------------------------------------
Since the August summary was issued, Peter Bowyer of the Canadian
Hurricane Centre has sent me some information on the effects of
Tropical Storm Dean in Newfoundland and on the Canadian marine banks.
As Dean crossed the southwestern Grand Banks on 28 August, many ships
and buoys to the right of the storm track and out to 200 nm reported
gale-force winds. There were no confirmed gales to the left of the
track, however. Hibernia (WMO 44145) reported south-southeasterlies
of 47 kts at an anemometer height ot 139 m just before Dean passed to
the north.
A large area of 4 to 6-metre seas was produced to the southeast of
the track across the southern Grand Banks. Ship PDHY (41.7N, 49.5W)
at 28/1800 UTC reported a wave of 5.7 m while Tail-of-the-Bank Buoy
(44140) experienced seas of 5.7 m at 1600 UTC approximately 120 nm
to the right of the track. At about the same distance to the left of
the storm's track, seas built to 3.5 m at the Nickerson Bank Buoy
(44251) at 1800 UTC.
Only light southeasterly winds of 10-15 kts were experienced over
Newfoundland. A band of rain displaced well to the north (250 to
300 nm) of Dean's track remained quasi-stationary over the eastern
portion of the island. Heavy rains occurred between midnight and
midday on the 28th from the Bonavista Peninsula to the Burin Peninsula.
Some of the highest storm totals include:
Bonavista - 107 mm
Lethbridge - 76 mm
St. Lawrence - 72 mm
The capital of Newfoundland, St. John's, recorded a much lower 24 mm
while Gander netted only 19 mm.
***********************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for September: 2 tropical depressions
2 tropical storms
3 hurricanes
NOTE: Much of the information presented below was obtained from the
TPC/NHC discussion bulletins issued with every regular advisory (CPHC
for locations west of 140W.) All references to sustained winds imply
a 1-min averaging period unless otherwise noted.
The narratives for all of the named storms were written by John
Wallace of San Antonio, Texas. Because of the interaction between
Gil and Henriette, those cyclones are covered in a single report.
A very special thanks to John for devoting much of his school holiday
time to working on the summaries.
Northeast Pacific Tropical Activity for September
-------------------------------------------------
The month of September was quite active in the Northeast Pacific
basin. Five tropical storms/hurricanes formed during the month, well
above the annual average of about three. Three of the storms reached
hurricane intensity with one becoming a major hurricane. The averages
for September are two hurricanes with one reaching major hurricane
intensity (Category 3+ on the Saffir/Simpson scale). Early in the
month Hurricane Gil and Tropical Storm Henriette moved in close
proximity to each other and engaged in a binary interaction. Around
mid-month Tropical Storm Ivo formed near the Mexican coast and prompted
the issuance of tropical storm warnings for portions of the Mexican
coastline. The storm, however, remained offshore with minimal impact
onshore.
The most significant cyclone of the month was Hurricane Juliette.
USAF Reserves Hurricane Hunters flew some missions into the hurricane,
and on one of these, measured a central pressure of 923 mb--the second
lowest pressure ever actually measured in an Eastern Pacific hurricane.
Juliette later brought tropical storm and hurricane conditions to
portions of the Baja California Peninsula. In its last gasp, Juliette,
after weaking to below depression status, exceptionally re-intensified
over the northern reaches of the narrow Gulf of California. The
system never regained tropical storm status but did generate some
well-organized, albeit shallow, convection. The final named cyclone
was short-lived Hurricane Kiko, which was a minimal hurricane for only
six hours.
In addition to the five systems mentioned above, two tropical
depressions formed in the Central North Pacific west of 140W. The
first of these, TD-01C, was very brief, being in advisory status for
only 18 hours on 11 September. The first advisory, issued by the CPHC
at 11/0000 UTC, placed the center about 400 nm southeast of Hilo. The
system was moving westward fairly quickly and was not forecast to
reach tropical storm intensity. By 1200 UTC the depression had lost
all its convection and the final advisory was issued at 1500 UTC,
placing the dissipating center about 400 nm south-southeast of South
Point on the Big Island.
Tropical Depression 02C formed about 750 nm southeast of Hilo on
23 September. Unlike its predecessor, TC-02C was forecast to intensify
into a tropical storm; however, this did not happen. The depression
sailed west-northwestward at a low latitude, passing about 500 nm
due south of South Point at 1200 UTC on the 24th. The forecast for
strengthening did not verify due to shear associated with an upper-
level trough west of the Hawaiian Islands, along with interference
from a weak disturbance near Johnston Island. The final CPHC advisory
was issued at 0900 UTC on 25 September and placed the dissipating
center about 650 nm south-southwest of Honolulu.
Hurricane Gil (TC-08E)
4 - 9 September
-----------------------
AND
Tropical Storm Henriette (TC-09E)
4 - 8 September
----------------------------------
A. Storm Origins
----------------
The track and development history of Hurricane Gil and Tropical
Storm Henriette is a classic case of direct tropical cyclone
interaction, also known as binary interaction, or the Fujiwhara effect.
Because of their interaction and almost identical life spans, the two
systems will be covered in a single summary.
The origin of Gil appears to be unrelated to a tropical wave. A
cyclonic disturbance first became apparent along the ITCZ on
2 September and steadily organized. By 0900 UTC on 4 September, the
LOW's organization on satellite imagery was sufficient to warrant its
upgrade to Tropical Depression Eight-E about 1075 nm west of
Manzanillo, Mexico. The tropical cyclone tracked slowly west-
northwestward, turning more westward as it was upgraded to Tropical
Storm Gil at 1800 UTC on 4 September, located some 1125 nm west of
Manzanillo.
Henriette's origin can apparently be traced back to a vigorous
tropical wave that exited the African coast on 24 August. It quickly
weakened, however, and tracked uneventfully across the basin. A LOW
formed along the wave axis on 1 September as it entered the tropical
Eastern Pacific and slowly organized. By 1500 UTC on 4 September
Dvorak estimates justified its upgrade to Tropical Depression Nine-E,
just six hours after Eight-E's first advisory, while located
approximately 275 nm west-southwest of Manzanillo. Its initial west-
northwesterly track turned more westward on the 5th. Easterly shear
from the same ridge that was its primary steering influence hindered
intensification. Nine-E was poorly-organized, and its future was in
doubt until a QuikScat pass supported its upgrade to Tropical Storm
Henriette at 2100 UTC on 5 September about 700 nm west of Manzanillo.
At this time, Gil and Henriette presented an odd pair--Henriette was
the larger circulation, but Gil was much better organized.
B. Track and Intensity History
------------------------------
Gil's westward motion slowed on the 5th, and it briefly stalled
while Nine-E/Henriette tracked steadily westward. At 0300 UTC on
6 September, Gil was upgraded to hurricane status while Henriette
remained a 40-kt tropical storm centered east-northeast of Gil.
Exactly when Gil and Henriette first interacted is uncertain, but
the interaction manifested itself in earnest beginning on the 6th.
Henriette's track changed from westerly to west-northwesterly while
accelerating slightly around Gil's northeast flank, in spite of being
the larger cyclone. Gil tracked slowly due west (perhaps "held back"
by Henriette) and strengthened, reaching its peak MSW of 85 kts and
minimum CP of 975 mb at 2100 UTC on 6 September roughly 1175 nm west-
southwest of Cabo San Lucas. Henriette intensified as well on the
6th and reached its peak MSW of 55 kts, with a CP of 994 mb, at 0300
UTC on 7 September while centered roughly 825 nm west of Cabo San
Lucas. At the time of its peak, Henriette was 460 nm northeast of Gil.
The overall track of both systems remained westerly, since it appears
that they were both embedded in a larger-scale gyre south of the
subtropical ridge.
Henriette weakened soon after its peak, in spite of excellent out-
flow, after crossing into unfavorably cool waters. It continued to
track west-northwestward at a brisk pace on the 7th to finally overtake
Gil in longitude on the 8th. Some detail should be given to the events
on the 7th and 8th, as these were arguably the most interesting days of
the interaction between the two systems.
Gil weakened on the 7th as well, due to interference from
Henriette's outflow. It maintained hurricane strength while it made
an abrupt turn to the northwest, bearing north-northwestward by the end
of the day. The magnitude of Henriette's influence on Gil is
interesting, considering that by 2100 UTC on the 7th, Henriette was
generating only weak convection while Gil remained a solid hurricane.
This suggests that the size of a tropical cyclone's circulation is more
important than its intensity in binary interaction. Perhaps Gil's
influence was dominant, however, and the necessarily reciprocal nature
of binary interaction only made it appear as if Henriette was the
dominant circulation. Given Henriette's ultimate fate, this is a
possibility. Perhaps more likely is that Henriette was the dominant
circulation at first but that it was eventually usurped by Gil by
virtue of its deterioration.
A weak Henriette overtook Gil in longitude early on the 8th. Gil's
forward motion, deliberate for most of its life, accelerated briefly
but dramatically to the north-northwest, peaking at 22 kts at 1500 UTC
on the 8th, at which time it weakened to tropical storm strength.
Gil's acceleration coincided with Henriette's comparably dramatic
acceleration and turn to the west-southwest as the two systems
co-revolved. The final advisory on Henriette, as a tropical
depression, was issued at 1500 UTC on 8 September with the center
located about 1125 nm east of Hilo, Hawaii. By the time of its last
advisory, Henriette was little more than a convectionless vortmax
lacking a closed circulation, centered some 250 nm west of Gil.
Gil scarcely fared better on the 8th. Shear, probably coupled with
cool SSTs, took a heavy toll on the tropical storm, and by late that
day Gil was a weakly convective whorl. Gil turned west-northwestward
on the 8th as part of the continued co-revolution with Henriette's
remnant LOW. On the 9th Gil was downgraded to a depression as it
turned west-southwestward. It feebly held on to tropical cyclone
status as stable air intruded into the system, further eroding its
already weak convection. The final advisory on Tropical Depression
Gil was issued at 2100 UTC on 9 September, placing the center about
970 nm east of Hilo. At the time of the final advisory, Gil's and
Henriette's remnants comprised two co-revolving LOWs embedded in a
larger cyclonic gyre. Henriette's remnant LOW apparently had
dissipated, or had been absorbed by Gil's remnant LOW, by the 10th.
Gil's remnant, however, remained identifiable until the 15th, after
which it dissipated in the Pacific well north of Hawaii.
C. Damage and Casualties
------------------------
No casualties or damage are known to have been caused by Gil or
Henriette as the two cyclones performed their do-si-do far removed
from any populated shores.
Tropical Storm Ivo (TC-10E)
10 - 14 September
----------------------------
A. Storm Origins
----------------
Ivo developed from a tropical wave--possibly of African origin--that
was first noted in the eastern Caribbean on the 3rd of September.
It tracked uneventfully across the Caribbean and Central America and
entered the eastern tropical Pacific on the 7th. A LOW formed along
the wave axis on the 10th and organized enough to warrant its upgrade
to Tropical Depression Ten-E at 2100 UTC that day, centered roughly
100 nm south-southwest of Acapulco, Mexico.
The cloud envelope of the incipient disturbance and Ten-E itself
were massive, but it was only superficially healthy. Initial Dvorak
ratings were low for a depression while easterly shear interfered
with its circulation. Ten-E tracked westward at first, south of a
mid-level ridge. At 0600 UTC on the 11th, ship ZDBE2 reported 37-kt
easterly winds and a 1006.5 mb pressure while located 135 nm north-
northeast of the center. This data, along with a Dvorak rating of
2.5 from TAFB, supported Ten-E's upgrade to Tropical Storm Ivo at
0900 UTC on 11 September about 225 nm south-southeast of Manzanillo.
B. Track and Intensity History
------------------------------
Ivo's track bent to the west-northwest after its upgrade, around
the periphery of the ridge to its north. This prompted the government
of Mexico to issue a tropical storm warning for the Pacific coast from
Acapulco to Cabo Corrientes at 0900 UTC on the 11th. The warnings
were discontinued east of Lazaro Cardenas at 1500 UTC and east of
Manzanillo at 2100 UTC the same day as Ivo paralleled the coast.
At 0300 UTC on the 12th, a tropical storm warning was issued for Baja
California from Cabo San Lucas to Cabo San Lazaro. Mexico dropped
the watches for the coast from Manzanillo to Cabo Corrientes at
0900 UTC on the 12th, roughly coinciding with Ivo's turn to the
northwest.
Ivo peaked at 1800 UTC on 12 September about 175 nm south of Cabo
San Lucas with a minimum CP of 998 mb and a 45-kt MSW. This slight
strengthening occurred in spite of continued mild northeasterly shear.
Ivo maintained this intensity for little more than a day before
weakening due to shear and cooler SSTs. At 2100 UTC on the 13th, all
warnings for Baja California were dropped. Ivo weakened quickly as
its convection collapsed--a ship just east of its center at 0600 UTC
on the 14th reported southeasterly winds of only 20 kts. This report
justified its downgrade to a depression at 0900 UTC that day with the
cyclone's track bending back toward the west as low-level steering
winds became dominant. The final advisory on the convection-free
vortex of Tropical Depression Ivo was issued at 2100 UTC on
14 September and placed the dissipating center about 425 nm west-
northwest of Cabo San Lucas. QuiKScat data indicated that Ivo's winds
were no higher than 25 kts at this time. Ivo's remnants were
indiscernible by late on the 16th.
C. Casualties and Damage
------------------------
Though rainbands from Ivo impacted the Mexican coast, no casualties
or significant damage are known at this time.
Hurricane Juliette (TC-11E)
21 September - 3 October
----------------------------
A. Storm Origins
----------------
The origin of Juliette is uncertain. Ostensibly, Juliette was a
redevelopment of Caribbean Tropical Depression Nine. There are a few
people in the meteorological community, however, who feel that
Juliette only formed within the larger convective envelope of the
post-Nine tropical disturbance and is thus only indirectly related
to TD Nine. For simplicity and clarity, in this summary it will be
presumed that Juliette was at least loosely related to Tropical
Depression Nine.
Tropical Depression Nine may have developed from a strong tropical
wave that exited the African coast around 12 September, though the
evidence linking it to TD Nine is tenuous. The wave that definitively
spawned TD Nine was first noted just east of the Lesser Antilles on
the 15th. On the 19th, a LOW formed along the wave axis--later that
day, satellite and surface analyses supported its upgrade to Tropical
Depression Nine at 2100 UTC. Even then its outflow was excellent and
its cloud pattern robust. Tropical storm watches were briefly issued
for the entire Caribbean coast from Nicaragua to Belize. They were
dropped when the depression made landfall on Nicaragua's sparsely-
populated Mosquito Coast near Puerto Cabezas at 0300 UTC on the 20th.
This was also the last advisory issued on Tropical Depression Nine.
The central convection of the remnant disturbance weakened over
Central America on the 20th. South of the center, however, convection
flared up over the extreme eastern Pacific as early as 1800 UTC that
day. By 0000 UTC on the 21st, this new convective center intensified
south of Guatemala and had a distinct cyclonic signature. Convection
was strong, but apparently the system's organization was insufficient
to issue warnings on. It was with some surprise that a Hurricane
Hunter mission into the system later that day found flight-level winds
of 52 kts at ~1520 m, corresponding to a surface wind of 40 kts.
Stepped-frequency radiometer data indicated a limited surface MSW of
50 kts. On the basis of this data, the disturbance was upgraded
directly to Tropical Storm Juliette in a special 1800 UTC advisory
on 21 September while located some 190 nm southeast of Puerto Angel,
Mexico. Juliette tracked west-northwestward, south of a mid-level
ridge. Though outflow was not impressive, very warm SSTs favored
further strengthening, though no one forecast the actual course of
events.
B. Track and Intensity History
------------------------------
Juliette's proximity to land prompted the hoisting of watches and
warnings for the southwestern Mexican coast, beginning with Juliette's
first advisory. These extended roughly from the Gulf of Tehuantepec
to Manzanillo and shifted westward on the 21st and 22nd. The watches
and warnings were dropped at 1500 UTC on the 22nd as Juliette pulled
away from the coast. The storm failed to thrive on the 22nd--deep
convection weakened and became asymmetric in spite of moderately
favorable upper-level conditions. A surprising development was an
abrupt southward shift of the center, while the overall heading
shifted to due west. This coincided with Juliette's weakening
convection. NHC staff stated that it was probably due to downslope
flow from the Isthmus of Tehuantepec.
A sustained intensification trend began late on the 22nd as
outflow improved and convection re-intensified over the center. The
first hints of an eye were apparent in satellite imagery by 2215 UTC
that day. Juliette's intensity took off on the 23rd--satellite
microwave imagery indicated that an eyewall was forming by about
0300 UTC, while at 1500 UTC satellite data warranted Juliette's
upgrade to hurricane status when located about 280 nm south-southeast
of Manzanillo. Juliette reached major hurricane intensity only six
hours later. A hurricane watch was concurrently issued for the south-
west coast of Mexico.
Juliette continued to explode in intensity on the 24th. At 0300
UTC the three-hour average Objective Dvorak T-number (ODT) was 7.0,
equivalent to a MSW of 140 kts. The constraints of the Dvorak
technique, however, meant that the official intensity was "only"
115 kts--the wind field needed time to "catch up" to the satellite
estimates. Juliette had a pinhole eye surrounded by a compact,
extremely cold CDO at this time. Its eye diameter was only 5 nm,
though its circulation was large and imposing. Juliette reached its
125-kt first peak in intensity at 0900 UTC on the 24th with an
estimated CP of 936 mb when located some 260 nm south-southeast of
Manzanillo. Juliette's CP dropped 53 mb in 24 hours for an average
rate of 2.2 mb per hour; this qualifies as rapid deepening. Between
2100 UTC on the 23rd and 0900 UTC on the 24th, the CP fell at an
average rate of 2.41 mb per hour, just short of the 12-hour mininum
criterion for explosive deepening (2.5 mb/hr for 12 hrs).
Juliette's intensity and organization flagged after its peak,
apparently due to an eyewall replacement cycle. A Hurricane Hunter
mission found flight-level winds (FLW) of only 90 kts in its southeast
quadrant at 1800 UTC and a 94-kt FLW in its northeast quadrant later
that day. Its estimated MSW dropped first to 100 kts, then to 90 kts
by 2100 UTC while its central pressure rose accordingly. The
hurricane soon re-intensified, however, and regained major hurricane
strength by 0300 UTC on the 25th. By 0900 UTC the three-hour ODT
was once again 7.0, and this time it was supported by a T7.0 from
the TAFB. Once again, however, the NHC intensity estimate remained
conservative until the Hurricane Hunters reached the system. The
conservatism was also based on an earlier upward bias of satellite
estimates, as determined by reconnaissance on the 24th.
The Hurricane Hunters finally reached Juliette late on the 25th
and found a Category 4 hurricane that was more intense than expected.
They recorded a FLW (at 700 mb) of 131 kts, and measured a
surprisingly low CP of 923 mb in Juliette's 9 nm-wide eye. Though
lower CPs have been estimated in NEP storms before (e.g., the 902 mb
CP of Hurricane Linda (1997)), this is the second-lowest CP actually
measured by reconnaissance, after 1973's Hurricane Ava (915 mb).
Although the conversion factor for FLW to surface MSW (0.9) suggested
surface winds of 120 kts, the 923 mb CP justified the NHC's increase
of the official MSW to 125 kts. This was Juliette's "true" peak
intensity, attained 415 nm south-southeast of Cabo San Lucas at
2100 UTC on 25 September. Dvorak intensity estimates from TAFB and
the AFWA were as high as 140 kts by 0300 UTC on the 26th while SAB
estimated 127 kts; the intensity remained 125 kts, however.
Juliette was a large hurricane, particularly for the NEP basin.
Hurricane-force wind radii were an impressive 60 nm, and 12 ft+ seas
extended as far as 325 nm from the center in its southern quadrant
at 0300 UTC on the 26th. Ship data from around 0000 UTC that day
revealed 34-kt wind radii as large as 225 nm in its eastern semi-
circle, placing storm-force winds perilously close to the Mexican
coast (18 nm offshore of Manzanillo). Tropical storm warnings were
accordingly re-issued for the southwest Mexican coast at 0300 UTC.
After tracking slowly west-northwestward for over two days, Juliette
made a long-forecast northwestward turn on the 26th, due to the ridge
to its north shifting eastward while a trough eroded its western limb.
The first watches were issued for Baja California at 0600 UTC that day.
Juliette weakened from its earlier peak, though it remained a major
hurricane throughout the 26th. Satellite imagery indicated, and a
reconnaissance mission found, concentric eyewalls on the 26th. A
flight late that day found an amazing three concentric eyewalls, though
they found no FLW higher than 93 kts. For a hurricane to have three
eyewalls is not unprecedented--three were found in the Atlantic's
Hurricane Edouard in 1996 (1)--but they are definitely one of the
curios of tropical meteorology. In any event, on the basis of their
data, Juliette was downgraded below major hurricane intensity at 0300
UTC on the 27th. The estimated MSW of 95 kts was considered generous
given the Hurricane Hunters' findings, but it was rather low for a
central pressure that was still as low as 942 mb. According to the
NHC's official statements, the discrepancy was probably due to the
broad central windfield of Juliette which didn't generate a strong
pressure gradient.
NOTE--A nice radar picture of the three concentric eyewalls can be
found at: http://www.hurricanehunters.com/juliette.htm>
The Mexican government issued the first hurricane warning for Baja
California at 0900 UTC on the 27th as Juliette turned due north. In
spite of persistent forecasts of a westward turn, Juliette continued
on this heading. The NHC considered its motion anomalous; indeed, one
forecaster said that Juliette seemed to be moving straight through a
ridge. Juliette slowly weakened as it tracked straight towards Baja
California. By 0300 UTC on the 28th, Juliette was only 45 nm
west-southwest of Cabo San Lucas, putting the region well-within the
radii of hurricane-force winds.
Early on the 28th, the Hurricane Hunters found a minimal hurricane
whose CP had risen approximately 1 mb per hour since their last fix.
Ship 4XFD reported 67-kt winds in the same region where reconnaissance
had reported FLW of 79 kts (the ratio of the surface winds to FLW,
0.85, agreed very well with the classic formulae for the conversion).
Again, reconnaissance found a central pressure that seemed to be too
low (971 mb) for the winds they found, supporting the NHC's conjecture
that the windfield was too broad to generate a higher MSW.
Juliette slowed on the 28th. Its motion became erratic, and it had
stalled by 2100 UTC as it weakened to tropical storm-strength some
65 nm west-northwest of Cabo San Lucas. The Mexican weather service
reported 52-kt sustained winds at Cabo San Lucas at this time as well
as a 93-kt gust at 0100 UTC the previous evening. An automatic
station at Cabo San Lucas reported a 76-kt wind at 0100 UTC on the
28th, though it is unclear if this were a sustained wind or a gust
(probably the latter)(2). The erratic motion was probably due to
Juliette finally "feeling" a ridge over the American Southwest
while the trough off California weakened and a ridge built in. This
left the storm in a col, a weak steering environment where it
lingered near the coast. It was the shape of things to come, as it
turned out.
Juliette surprised forecasters by re-intensifying to hurricane
strength at 0300 UTC on 29 September, 65 nm northwest of Cabo San
Lucas, while remaining stationary. Satellite estimates suggested that
the storm intensified even as it was mostly over land, though that
fact was key to the NHC's conservatism in the intensity estimate.
Both Cabo San Lucas and La Paz reported only light rain and below-
storm-force winds at this time. Apparently most of Juliette's rain
and winds were over remote, mountainous regions. Juliette weakened
again to a tropical storm at 1500 UTC on the 29th, apparently just
over the west coast of Baja California near Todos Santos. Weakening
began apace on the 29th, due to dry air entrainment, land interaction,
and wind shear. Juliette's center passed very close or over the
island of Santa Margarita, just off the west coast of Baja California,
at 0000 UTC on the 30th as it finally moved out of its stall and
assumed a meandering, roughly northwestward track offshore.
Juliette weakened to a depression as it turned north again on the
30th, making landfall at Cabo San Lazaro at approximately 0800 UTC.
It tracked northward, straddling the coast, and moved inland over the
peninsula. Steering currents remained light as the system was
apparently embedded in a mid-level ridge. Though its central
convection was weak, convection persisted over the Gulf of California
and the adjacent land areas. A 40-kt gust recorded at Santa Rosalia
was discounted by the NHC as spurious, since it was discordant with
earlier data from that station and inconsistent with satellite data.
At 2100 UTC on the 30th, Juliette's center re-formed over the Gulf of
California, roughly 15 nm southeast of Tiburon Island. Even so,
satellite and surface data discrepancies made pinpointing its
location and intensity difficult. Juliette was embedded in a larger
cyclonic gyre that had a significant influence on its motion.
The final advisory on Juliette was issued at 0300 UTC on 1 October
after its low-level circulation decoupled from the rest of the cyclone.
Its poorly-defined center was placed inland over the Sonoran coast,
some 20-25 nm north of Tiburon Island. In yet another surprise for
forecasters, the remnant LOW's convection and circulation regenerated
over the Gulf of California on the 1st, warranting its re-upgrade
to a depression at 0300 UTC on 2 October some 55 nm south-southeast
of Puerto Penasco, Mexico. Althought Juliette was almost
unclassifiable by the Dvorak technique, WSR-88D data from Yuma,
Arizona, revealed good banding and winds as high as 35-50 kts at
0900 UTC. The latter winds, however, were well above sea level, and
it was deemed unlikely that the high winds would have worked down to
the surface due to the system's weak convection.
Juliette meandered toward the northwest over the far northern Gulf
of California on the 2nd before weakening once again. It turned
southwestward late on the second, as the deep-layer LOW it was embedded
in was deflected southwards by a ridge over the Pacific. The second
final advisory on Tropical Depression Juliette was issued at 0300 UTC
on 3 October as it made landfall about 80 nm south-southeast of San
Felipe, Mexico.
C. Meteorological Observations
------------------------------
Juliette lingered off southern Baja California for days, resulting
in some impressive rainfall totals for a usually arid region. One
government official was quoted as saying that Cabo San Lucas received
457 mm of rain in four days, equivalent to the total of four average
rainy seasons. The highest 24-hour totals were: 136 mm at Santiago
(Baja California Sur) on the 27th, 167.5 mm at Enpalme (Sonora) on
the 30th, and 207.2 mm at San Felipe (Baja California) on 2 October
(3).
D. Damage and Casualties
------------------------
The estimated damage in Baja California was minor, roughly
$12 million according to press reports. The Associated Press stated
that in Cabo San Lucas, a resort city of 25,000, Juliette smashed
docks, uprooted trees and power lines, and broke the city's water
mains. Many tourists were stranded in Cabo San Lucas for the storm's
duration as floodwaters washed out the main bridge to the mainland
and blocked smaller roads. Damage to the homes of the poor was
significant, while most luxury hotels received only minor damage.
One hotel, however, suffered 90% damage according to AP sources.
In southwestern Mexico, heavy rains from Juliette flooded 200 homes
in the state of Michoacan and downed many trees. There was minor
flooding and tree damage in Acapulco, while rain-swollen rivers knocked
out two bridges in the state of Oaxaca.
Three deaths resulting from Juliette are known at present. One man
drowned when his boat capsized near the Mexico mainland while a fisher-
man from Acapulco was lost in high seas. A Colorado surfer drowned in
rough waves and was the only American casualty.
E. References
-------------
(1.) Weatherwise. February/March 1997, p. 40.
(2.) "Ciclon Tropical Juliette." Servicio Meteorológico Nacional
http://smn.cna.gob.mx/ciclones/tempo2001/pacifico/juliette/
juliette.html>
(3.) Ibid.
Hurricane Kiko (TC-12E)
22-25 September
------------------------
A. Storm Origins
----------------
Kiko developed from a tropical wave that was first noted in the
Eastern Pacific on 19 September. By late on the 21st, a definite
cyclonic disturbance had formed along the wave axis. The organization
of this disturbance improved, warranting its upgrade to Tropical
Depression Twelve-E at 0300 UTC on 22 September about 800 nm west-
southwest of Manzanillo, Mexico.
Although conditions seemed to be favorable for significant
strengthening at first, easterly shear slowed intensification while an
approaching trough restricted its outflow. This combination of factors
made positioning the center difficult. Early on, an initial west-
northwestward track was found to be northwesterly when the first good
visible imagery became available on the 22nd. Difficulties aside, the
depression became organized enough to be upgraded to Tropical Storm
Kiko at 2100 UTC on 22 September when located about 950 nm west of
Manzanillo. About this time Kiko's track became due westerly as it
moved south of the climatological subtropical ridge. The NHC stated
that the westward turn may have been due to the realignment of Kiko's
LLCC with its deep convection as outflow improved.
B. Track and Intensity History
------------------------------
Kiko intensified slowly through the 23rd, perhaps due to the
entrainment of stable air into its western semicircle late that day.
Even so, microwave satellite imagery revealed eye formation late on
the 23rd. Therefore, at 0900 UTC on 24 September, Kiko was upgraded
to hurricane status roughly 1225 nm west of Manzanillo with 65-kt MSW
and a CP of 987 mb. This was Kiko's peak intensity. At this time,
microwave imagery revealed a 20-nm eye, supported by infrared imagery
and Dvorak intensity analyses. Kiko's upgrade coincided with a brief
west-northwestward jog before a westward track resumed late on the
24th. Interestingly, the NHC also speculates that the decrease in
Kiko's forward motion commencing on the 23rd may have also been due
to the re-organization and regeneration of its central convection.
Kiko weakened to tropical storm-strength soon after its peak due to
cooler waters and increased shear. Kiko's deterioration was relatively
rapid and it was downgraded to a depression at 1500 UTC on the 25th.
The final advisory on Tropical Depression Kiko was issued at 2100 UTC
on 25 September when it was located some 1425 nm west of Manzanillo.
Kiko was arguably more remarkable in death than it was in life.
The storm's remnant was recognizable long after the final advisory was
issued and generated intermittent deep convection until the 28th as it
drifted westward across the Pacific. The low-level vortmax persisted
longer still, and its convection even flared up once again as an extra-
tropical cyclone approached. A cold front associated with the LOW
finally absorbed Kiko's remnant by 0600 UTC on 2 October, well north-
east of Hawaii.
C. Damage and Casualties
------------------------
No casualties or damage are known to have resulted from Kiko.
***********************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for September: 2 tropical depressions **
5 typhoons
** - Both of these systems were treated as tropical depressions by
JMA and some of the other Asian TCWCs, but not by JTWC
NOTE: Most of the information on each cyclone's history presented in
the narrative will be based upon JTWC's advisories, and references to
winds should be understood as a 1-min avg MSW unless otherwise noted.
However, in the accompanying tracking document I have made comparisons
of coordinates with some of the Asian warning centers when their
positions differed from JTWC's by usually 40-50 nm or more. A special
thanks to Michael V. Padua, owner of the Typhoon 2000 website, for
sending me the PAGASA and JMA tracks. Also, a special thanks to
Huang Chunliang of Fuzhou City, China, for sending me tracks based on
warnings from the National Meteorological Center of China (NMCC), the
Hong Kong Observatory (HKO), and the Central Weather Bureau of
Taiwan (CWBT).
In addition, Roger Edson of the University of Guam sent me tracks
for two tropical depressions which were warned on by some of the Asian
TCWCs but not by JTWC. A special thanks to Roger for the information
he sent.
In the title line for each storm I plan to reference all the cyclone
names/numbers I have available: JTWC's depression number, the
JMA-assigned name (if any), JMA's tropical storm numeric designator,
and PAGASA's name for systems forming in or passing through their area
of responsibility.
Northwest Pacific Tropical Activity for September
-------------------------------------------------
The Northwest Pacific basin was very active during the months of
September. Five tropical cyclones were named by RSMC Tokyo and all
reached typhoon intensity. Typhoon Danas clipped the southeastern
corner of Japan and caused a few fatalities and some flooding. Two
of the storms, Nari and Lekima, brought destructive floods to Taiwan
with Nari being especially deadly. Typhoons Vipa and Francisco both
recurved northeastward into the North Pacific with no effects on land.
Two additional systems were tracked as tropical depressions by JMA
and some of the other warning centers. Roger Edson also provided me
with tracks for these systems. Since these depressions were operating
simultaneously and, based on Roger's assessment, there is a possibility
they could have reached minimal tropical storm intensity, in the tracks
file I identified them with the Greek letters "Rho" and "Sigma". The
first system, "Rho", was active in some form or another from the 5th
until the 12th of September. It originated as a weak LOW in the Gulf
of Tonkin east of Hanoi, drifted very slowly eastward across the
Luichow Peninsula, reaching a point about 225 nm south-southwest of
Hong Kong by 1200 UTC on 8 September, then drifted southward and
eventually back to the west. The system became slightly better
organized on the 9th, and on 10 September made landfall around 0200
UTC near Lingshui Li Autonomous County of Hainan Province. The
depression continued westward across Hainan Dao, re-entering the
Gulf of Tonkin once more, and eventually moved inland into southern
China where it dissipated on the 12th.
Qiongshan City recorded 160 mm of rain from the night of the 7th
through the afternoon of the 8th, and a three-day storm total in
excess of 210 mm. Wenchang City recorded 115 mm in an eight-hour
period on the 8th and 217 mm in a 54-hour period ending at 0600 UTC
on 10 September. Haikou City measured 127 mm of rain during the
same 54-hour period and 155 mm for a three-day total. One person
was injured and 15 houses destroyed in a tornado which lasted a few
minutes in Xiuying District, Haikou City around 0840 UTC on the 10th.
(The above information was sent to me by Huang Chunliang.)
The second depression, "Sigma", formed south of Taiwan on the 7th
and moved generally northeastward over the next several days. JMA
elevated the 10-min avg winds to 30 kts for a 24-hour period beginning
at 09/0000 UTC when the system was located about 100 nm east-southeast
of the southern tip of Taiwan. It was at this juncture that Roger
Edson assigned a 1-min avg MSW of 35 kts. The most notable aspect
of this depression was its interaction with Typhoon Nari which was
likely one of the factors contributing to Nari's highly erratic track.
The depression continued moving northeastward, passing south of
Okinawa on the 10th, and had weakened into a weak LOW south of Japan
by the 12th. Both "Rho" and "Sigma" were mentioned by JTWC in their
daily STWOs, but no warnings were issued on either system.
Typhoon Danas (TC-19W / TY 0115)
2 - 14 September
---------------------------------
Danas: contributed by the Philippines, is a Tagalog word meaning
"to feel" or "to experience"
A. Storm Origins
----------------
JTWC issued a STWO at 0200 UTC on 2 September which noted that an
area of convection had formed about 450 nm west of Wake Island. A
LLCC with persistent convection was developing in a col area south of
a TUTT cell. Diffluence southeast of the trough was creating a fairly
favorable environment for development. Although the first JTWC warning
was not issued until 03/0000 UTC, the JMV file (a sort of working Best
Track) indicates that the system had become a 25-kt depression at
0600 UTC when located about 500 nm west of Wake Island. A TCFA was
issued at 2130 UTC as an increase in the areal coverage of deep
convection had been noted during the previous few hours.
JTWC issued the first warning on Tropical Depression 19W at 0000 UTC
on 3 September. The system was centered about 600 nm west of Wake
Island or about 570 nm east of the Northern Marianas. Maximum winds
were estimated at 25 kts and the depression was moving westward at
5 kts. Convective organization was increasing, and at 1200 UTC the
MSW was bumped up to 30 kts with deep convection building over the
LLCC. At 0000 UTC on the 4th both JTWC and JMA upgraded the
strengthening tropical cyclone to tropical storm status with JMA
assigning the name Danas. The newly-christened Danas was then located
about 450 nm east of the Northern Marianas, moving westward at 10 kts.
B. Track and Intensity History
------------------------------
Initially steered westward by a subtropical ridge to the north,
Danas gradually slowed and turned northward as a baroclinic trough
east of Honshu moved eastward. The cyclone intensified rather
quickly after reaching tropical storm strength. The intensity
estimates at 0600 and 1200 UTC on 4 September are good illustrations
of the situation often faced by forecasters when they must choose
between widely varying satellite intensity estimates. At 04/0600
UTC both JTWC and JMA reported 45 kts (1-min and 10-min averages,
respectively). Satellite CI estimates at the time were 30, 45, and
55 kts. Six hours later JTWC's 1-min avg MSW was 60 kts and JMA's
10-min mean MSW was 55 kts--satellite estimates ranged from 45 to
65 kts. JTWC upgraded Danas to typhoon status at 1800 UTC with the
center located approximately 350 nm east of the Northern Marianas.
The intensity was upped to 80 kts at 05/0000 UTC while at the same
time JMA classified the storm as a 70-kt typhoon. Danas by this
time was moving northward at 6 kts.
JTWC increased the MSW to 85 kts at 05/1800 UTC. A 05/2006 UTC
SSM/I pass depicted a small eye feature with good convective banding
in the eastern semicircle. Upper-level outflow was good, especially
toward the southeast. By 0600 UTC on the 6th satellite imagery
revealed a 15-nm round cloud-filled eye in the center of the CDO.
The trough which had brought about the northward turn began to fill
and the ridge to the north of the typhoon began to strengthen--by
1200 UTC Danas was beginning to move in a north-northwesterly
direction which gradually became northwesterly. The storm reached
its peak intensity of 115 kts (per JTWC's warnings) at 0000 UTC on
7 September when the eye was centered approximately 400 nm east-
northeast of Iwo Jima. The MSW was based on CI estimates of 115 and
127 kts. Danas maintained its peak intensity for 18 hours. A SSM/I
pass at 07/1023 UTC revealed a tight, symmetrical system with an
8-nm diameter cloud-filled eye and a primary banding feature over
the southeast quadrant.
By 08/0000 UTC Typhoon Danas was moving due westward as it was
being steered by an intense mid-level HIGH situated east of Japan.
The intensity had come down a bit to 105 kts at 1800 UTC on the 7th,
although one satellite intensity estimate was still at 127 kts. JTWC
lowered the MSW to 100 kts at 0600 UTC, but raised it back to 105 kts
at 1200 UTC based on Dvorak intensity estimates ranging from 90 to
115 kts. At 08/1800 UTC Danas had turned to the northwest as it
passed about 235 nm due north of Iwo Jima. The storm was also located
about 430 nm south-southeast of Tokyo and was beginning to pose a
distinct threat to Japan. Typhoon Danas continued moving northwest-
ward toward southwestern Honshu until it reached its point of
recurvature around 0000 UTC on 10 September about 235 nm southwest of
Tokyo. An approaching mid-latitude trough had weakened the ridge
which had been steering the storm, allowing it to recurve rather
abruptly to the north-northeast. Fortunately, Danas began to weaken
steadily as it approached Honshu. The MSW was down to 85 kts by 0000
UTC and continued to drop as the typhoon approached the Tokyo area.
At 1200 UTC the 35-nm diameter banding eye of Danas was located
about 150 nm southwest of Tokyo and moving north-northeastward at
7 kts. The MSW was 75 kts at that time and had dropped to an
estimated 70 kts by the time the eye reached the coast just southwest
of Yokosuka at 11/0035 UTC. (Yokosuka is a short distance south of
Tokyo on a point of land extending out into Tokyo Bay.) The
NAVPACMETOCCEN Yokosuka reported sustained winds of 65 kts from the
southeast gusting to 75 kts as the storm made landfall. (JMA's 10-min
avg MSW at 0000 UTC was 55 kts.) Danas moved across the peninsula
southeast of Tokyo and by 0600 UTC was moving out into the Pacific
about 60 nm northeast of Tokyo. JTWC downgraded Danas to a 60-kt
tropical storm at this time. (Interestingly, one satellite intensity
estimate was still as high as 77 kts.) After crossing extreme south-
eastern Honshu the former typhoon accelerated northeastward and
weakened as it began to transition into an extratropical cyclone.
The final JTWC warning on Danas was issued at 12/0600 UTC. The storm
had completed extratropical transition and was located well east of
Hokkaido and south of the Kuril Islands, racing northeastward at
22 kts. The extratropical gale continued to moved northeastward, then
curved eastward as it approached the 49th parallel. By 0600 UTC on
14 September the system was still a 45-kt gale south of the south-
western Aleutian Islands.
Typhoon Danas was at its peak intensity of 115 kts from 07/0000
through 07/1800 UTC. The minimum central pressure estimated by JMA
was 950 mb. Danas was an average-sized typhoon. At its peak
intensity storm-force winds extended outward from the center 80 nm
in the eastern semicircle and 50 nm to the west while gales covered
an area about 300 nm in diameter. By the time the typhoon was
approaching Japan the gale-force radii had expanded--gales extended
outward 190 nm to the northeast and southeast and 160 nm to the north-
west of the center.
C. Meteorological Observations
------------------------------
The only report available was the observation from Yokosuka which
was referenced in the above section.
D. Comparison Between JTWC and Other Centers
--------------------------------------------
Center position coordinates between the various warning centers
were in very good agreement for Typhoon Danas. Intensity estimates
between JTWC and JMA were in good agreement except for the storm's
most intense phase. JMA's peak 10-min avg MSW was 80 kts, and was
kept at this value for a full four days, from 06/0000 through 10/0000
UTC, except for a six-hour period on the 8th when it was lowered to
75 kts. JTWC's 1-min avg MSW estimates were at 100 kts or greater
for most of this period, peaking at 115 kts on the 7th. NMCC's
peak estimated intensity (10-min avg) was 90 kts, from 0600 UTC on
8 September through 0000 UTC on the 10th. During the time when JTWC's
MSW was at 115 kts, NMCC's 10-min mean wind was 80 kts.
E. Damage and Casualties
------------------------
According to press reports, five persons died in Japan as a result
of Typhoon Danas. Four of the deaths were due to mudslides--the other
fatality was a 50-year-old man who fell from the roof of his house
while carrying out repairs. In addition, fifteen persons were
injured, mainly by flying debris.
The town of Nikko, north of Tokyo, recorded in excess of 870 mm of
rain over a four day period. Flooding was reported by 148 homeowners
in several prefectures, and over 220 households were advised to
evacuate due to the threat of floods and mudslides. Several trees
were blown down across streets in the downtown Akasaka area, crushing
one car, but no injuries were reported.
Ferry services between Honshu and outlying islands were disrupted,
more than 140 domestic and international flights cancelled, and
services on a number of train lines in and around Tokyo cut back.
Danas' high winds and heavy rains also shut down some of the high-speed
bullet trains, leaving thousands of passengers stranded.
Typhoon Nari (TC-20W / TY 0116 / Kiko)
5 - 21 September
---------------------------------------
Nari: contributed by South Korea, is the lily, a wildflower commonly
observed in the summer in Korea
A. Storm Origins
----------------
The disturbance which became the long-lived and erratic Nari had its
origin in the Philippine Sea in late August. An area of convection
had formed by 0600 UTC on 31 August roughly midway between northern
Luzon and the Northern Marianas. A broad cyclonic circulation with
westerly winds equatorward of the center was located in the region, and
there was some isolated convection noted along the southern periphery
of the circulation. A 200-mb analysis and CIMSS products indicated
moderate vertical shear over the region. The disturbance remained
quasi-stationary and by 2 September had weakened and was no longer
considered a suspect area for tropical cyclogenesis. On the 3rd the
area of convection redeveloped farther west in association with a
monsoon trough in the region. A QuikScat pass on the 4th depicted a
weak LLCC located about 150 nm north of the previous day's position.
Things got interesting on the 5th! Based on JTWC's STWO, the
disturbance moved northwestward to a position east of southern Taiwan.
JMA, however, classified the system as a weak tropical depression at
1200 UTC, located about 265 nm west-southwest of Okinawa. At 1800 UTC
winds were increased to 30 kts (10-min avg). JTWC had assessed the
potential for development to be fair at 1200 UTC, and at 1930 UTC a
TCFA was issued, noting an improvement in the coverage and organization
of deep convection. At 0000 UTC on 6 September JMA upgraded the system
to Tropical Storm Nari, located about 200 nm west-southwest of Okinawa.
At the same time JTWC initiated warnings on Tropical Depression 20W
with 25-kt winds. JTWC's position was about 55 nm west-northwest of
JMA's, or about 100 nm east of Taipei, Taiwan. The JTWC warning noted
that the center was fully-exposed to the east of a line of deep
convection.
JMA's intensity remained at 35 kts throughout the 6th while JTWC
kept the system at depression status, based on CI estimates of 25 and
30 kts. Enhanced infrared imagery depicted a very weak, diffuse system
with a partially-exposed center. Several bursts of deep convection
were noted around 1800 UTC, so JTWC increased the MSW to 30 kts. Radar
imagery revealed a well-defined mid and lower-level circulation center
near the bursts of deep convection. An amended 1800 UTC warning was
soon issued upgrading Nari to tropical storm status based on synoptic
reports from Okinawa which showed rapid pressure falls and winds near
gale force. (Satellite CI estimates at the time were still 25 and
30 kts.) Nari was centered at this time only about 50 nm west of
Okinawa, moving east-northeastward at 7 kts.
B. Track and Intensity History
------------------------------
The track of Tropical Storm/Typhoon Nari over the next 5 or 6 days
after it was named was extremely erratic and convoluted with twists,
turns, and loops within loops. It remains to be seen if the final
"best track" for Nari will smooth out any of the kinks, but during this
period the storm was within easy radar coverage range from Okinawa
and the coordinates from JTWC, JMA, and NMCC were in excellent agree-
ment. Later, as the storm approached Taiwan, the Taipei radar helped
to pinpoint the eye, so again there was little discrepancy between
the warning centers as to the exact location of Nari's center. In
order to try to present the Nari saga as it unfolded in a clear and
orderly manner, I am going to adopt an approach which I've considered
on several occasions in the past but have never implemented--a daily
diary format. (Dates represent day boundaries in UTC.)
September 7th: At 0000 UTC Nari's center was located approximately
13 nm south of Kadena AB, moving slowly eastward at 7 kts. The MSW
was estimated at 45 kts, based mainly on synoptic reports--satellite
intensity estimates were lower. The storm continued drifting eastward
and by 0600 UTC had reached a point about 25 nm east of Kadena where
it remained essentially stationary for several hours before reversing
its motion and drifting back toward the west. Nari also intensified
as bursts of deep convection developed near the center, leading to the
MSW being upped to 50 kts at 1200 UTC. By 1800 UTC the storm's center
had drifted back westward and was located essentially over Kadena AB.
Based on synoptic reports JTWC upgraded Nari to a 70-kt typhoon at
this time while JMA and NMCC had increased their 10-min avg MSW
estimates to 55 kts and 50 kts, respectively. Nari was a small cyclone
with 50-kt winds confined to a zone within 20 nm of the center.
September 8th: For most of 8 September Nari drifted initially north-
westward, later turning to a westerly track. By 1800 UTC the typhoon's
center had reached a point about 140 nm west-northwest of Kadena AB.
JTWC brought the MSW down to 65 kts at 1200 UTC where it remained for
24 hours while JMA's and NMCC's intensity estimates remained at 60 kts.
Nari had entered Taiwan's AOR by 1800 UTC and CWBT assessed the 10-min
avg MSW at 60 kts also. The storm remained small with gales covering
an area no more than 100 nm in diameter.
September 9th: Nari's westward motion came to a halt early on the 9th
and the storm sat essentially stationary at a position about 150 nm
west-northwest of Kadena AB. The storm's organization improved during
the day with satellite intensity estimates reaching T4.5 (77 kts). An
08/2151 UTC TRMM pass had depicted tightly-wrapped but narrow
convective banding. JTWC increased the MSW to 75 kts at 0600 UTC and
NMCC upgraded Nari to typhoon status at the same time. At 1200 UTC
NMCC increased their 10-min avg MSW estimate to 70 kts while HKO and
CWBT both upgraded Nari to a typhoon. JMA had dropped their reported
intensity early in the day, but bumped it back up to 60 kts at 1200
UTC. Nari's areal dimensions had increased somewhat by 1800 UTC with
gales covering an area over 150 nm in diameter.
September 10th: Nari commenced a southward drift early on the 10th
which later became east-southeastward. By 1800 UTC the storm had
moved to a point roughly 85 nm west-southwest of Kadena where it then
remained quasi-stationary for about 48 hours. Nari weakened some,
likely due to the upwelling of cooler water in the area where it had
been loitering. JTWC reduced Nari's intensty to 65 kts at 0000 UTC
while NMCC made a more drastic reduction from 70 to 50 kts. JMA's
10-min avg MSW estimate remained at 60 kts through the 10th. As the
storm pulled away from the area where it had sat stationary on the 9th,
it began to show signs of intensifying once more. NMCC upped their
intensity to 60 kts at 1200 UTC, and JTWC increased their 1-min avg
MSW to 75 kts once again at 1800 UTC.
September 11th and 12th: On these two days Typhoon Nari was quasi-
stationary approximately 40-50 nm west of Kadena. The storm wiggled
about some, seeming to describe a very tight clockwise loop within
a larger counterclockwise loop. The re-intensification trend noted
on the 10th continued--at 11/0000 UTC satellite imagery indicated that
a 5-nm irregular eye had developed with an increase in deep convection
over the eastern quadrant. The eye diameter had increased to 10-nm
by 0600 UTC and CI estimates had reached 102 kts. At 1200 UTC
satellite intensity estimates were 102 and 115 kts, so JTWC upped the
MSW to 100 kts, which was the peak intensity for Typhoon Nari. The
storm's eye at this time was only about 35 nm west of Kadena and 50-kt
winds reached outward 35 nm from the center. A gradual weakening
trend began afterward, once more likely due to upwelling of cooler
waters, and winds had come down to 75 kts by 1800 UTC on the 12th (per
JTWC). A SSM/I pass at 12/1236 UTC indicated that the convection
associated with the vortex had expanded and weakened. JMA's peak
intensity for Nari was 85 kts while NMCC's was slightly lower at
80 kts. Both these warning centers had reduced Nari to a 60-kt
tropical storm by 1800 UTC on the 12th. The area covered by gales
had expanded to cover a zone almost 200 nm in diameter.
September 13th: By 13/0000 UTC Nari was located about 70 nm west of
Kadena and had begun to track slowly toward the west-northwest. At
1200 UTC the typhoon was about 120 nm west-northwest of Kadena and had
crossed its track of five days earlier, completing a counterclockwise
loop which contained a tiny clockwise loop. The storm had briefly
moved northwest to this point, then moved little for the remainder of
the 13th. Nari's intensity remained basically static--JTWC decreased
the MSW to 65 kts at 0600 UTC but bumped it back up to 70 kts at 1800
UTC. JMA's and NMCC's 10-min avg MSW remained pegged at 60 kts, and
after Nari re-entered CWBT's AOR at 0600 UTC, that agency estimated
the intensity at 60 kts.
September 14th: On 14 September Nari weakened slightly, being down-
graded to a 60-kt tropical storm by JTWC at 1800 UTC. The other
warning centers' 10-min avg MSW estimates likewise remained under
typhoon intensity, including that from HKO (Nari had re-entered that
center's AOR by 14/0600 UTC). The slow northwestward motion seen the
previous day came to a halt about 235 nm northeast of Taipei, and by
1800 UTC a slow southwestward drift had begun.
September 15th: Nari turned more to the south-southwest as the 15th
began, and for much of the day moved in that direction at a steady
6 kts, but slowed and turned slightly back to the west-southwest late
in the day. By 1800 UTC the storm's 22-nm diameter eye was centered
approximately 115 nm east-northeast of Taipei. The weakening observed
on the previous day proved to be temporary--late on the 14th animated
satellite imagery revealed a redeveloping banding eye feature and CI
estimates were 65 kts, so JTWC upgraded Nari back to typhoon status
after only six hours as a tropical storm. As the day progressed the
eye became more distinct and the areal coverage of deep convection
increased. JTWC had increased the MSW back to 80 kts by 1800 UTC,
and all the other agencies had re-upgraded Nari to typhoon status by
1200 UTC.
September 16th: By 16/0000 UTC Nari was located about 100 nm east-
northeast of Taipei and drifting westward at 3 kts. This motion later
became southwesterly at a slightly faster pace as the day wore on.
JTWC increased the MSW to 90 kts at 0000 UTC based on CI estimates of
77 and 102 kts. Gales reached out about 100 nm from the 25-nm round
eye. By 1200 UTC Nari's eye was nearing the coast of northeastern
Taiwan and made landfall around 1500 UTC just east of the city of Lo
Tung. JTWC estimated the maximum winds at landfall to be 85 kts
sustained, gusting to 105 kts. By 1800 UTC the center was inland and
weakening as it tracked to the southwest at 8 kts. JMA did not
increase Nari's intensity (10-min avg) above 65 kts during this
secondary peak, but both NMCC and CWBT raised their estimates to
80 kts, and HKO was reporting 75 kts just before landfall.
September 17th and 18th: Nari had weakened to a tropical storm by
17/0000 UTC (according to all warning centers) as it drifted slowly
south-southwestward over Taiwan. Whereas the center coordinates from
the various warning agencies agreed exceptionally well during the time
Nari was fairly well-organized and within radar range of Kadena and/or
Taipei, during the 17th and 18th the position estimates became rather
divergent--not unexpected with a weakening system over land. But in
general all the TCWCs except JMA tracked Nari's center down the
western side of the island. JMA, however, tracked the storm's center
southward just off the eastern coast of Taiwan. JTWC's positions at
0600 and 1200 UTC on 18 September abruptly jumped eastward to near the
eastern side of the island, but the 1800 UTC position was back to just
west of southwestern Taiwan. All the warning agencies maintained
Nari at tropical storm intensity throughout the 17th and 18th except
for JTWC and NMCC, who downgraded the storm to depression status at
18/1800 UTC. While the exact location of the center may not be known
with certainty during these two days, the storm's slow drift down the
backbone of Taiwan led to very heavy rainfall over the island which
had disastrous consequences. More on this below. (By 16/1800 UTC
Nari had entered PAGASA's AOR and that agency began issuing warnings
on the cyclone, naming it Kiko--a Filipino nickname.)
September 19th: After all the surprises which this long-lived and
erratic cyclone had brought, Nari still had one more trick up its
sleeve. After clearing Taiwan Tropical Depression Nari turned westward
across the Taiwan Strait. Satellite CI estimates were initially at
30 kts, but the JTWC warning issued at 1200 UTC noted the receipt of
a 35-kt CI estimate. By 1800 UTC intensity estimates had reached
45 kts, so JTWC upgraded Nari to a 45-kt tropical storm located about
225 nm east of Hong Kong. A 19/1628 UTC SSM/I pass depicted the
possible development of a banding eye. The cyclone had by this time
exited the AORs of Taipei and Manila, so those TCWCs were no longer
players. NMCC also upgraded Nari back to tropical storm status at
19/1800 UTC with the 10-min avg MSW estimated at 40 kts. HKO, which
had never downgraded Nari, raised its intensity estimate back to
40 kts.
September 20th: Early on the 20th animated visible and infrared
imagery revealed a developing banding eye and improving organization
of the deep convection. JTWC increased the MSW to 55 kts at 20/0000
UTC with Nari centered about 155 nm east of Hong Kong. HKO upped their
10-min avg MSW estimate to 50 kts, and NMCC raised theirs to 60 kts,
which, following the standard 10-min to 1-min conversion rule, would
imply a 1-min avg MSW of about 70 kts. Nari's westward motion picked
up some as it neared the Chinese coast. At 0600 UTC the center of
the storm was just making landfall about 80 nm east-northeast of Hong
Kong with 55-kt winds based on JTWC's warning. HKO's and NMCC's 10-min
avg MSW estimates had fallen to 40 kts, but both those agencies were
placing the center to the north and west of JTWC's position and hence
a little farther inland. As Nari continued westward into China the
convection began to weaken rapidly, and by 0000 UTC on 21 September
the system was a weak 20-kt LOW located about 150 nm west-northwest
of Hong Kong. Interestingly, during this final encore to Nari's long
performance, JMA never increased the intensity above 30 kts, somewhat
surprising considering the consensus among the other warning c