[Index]
Monthly Global Tropical Cyclone Summary December 1999
[Summaries and Track Data] [Prepared by Gary Padgett]
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Cyclones
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Monthly Global Tropical Cyclone Summary December 1999 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
DECEMBER, 1999
(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 - Satellite Analysis Branch Website
------------------------------------------------
Sheldon Kusselson, a Meteorologist with the Satellite Analysis
Branch/NESDIS, wrote me and sent some information regarding their
website which he thought I might like to pass along. The URL is:
http://www.ssd.noaa.gov/>. Sheldon writes: "Click on Operational
Products and Services, then under SSD Products and Hazard Support,
go to Tropical Cyclones - Position and Intensity. Clicking on Tropical
Cyclones - Position and Intensity will give you our Bulletins that we
send out for the Eastern Hemisphere, SAB-coordinated positions with
TPC and CPHC for the Western Hemisphere, Tropical Rainfall Potential
using microwave data, and (this should really be of interest to your
readers) real-time satellite data (including microwave data), at least
for now for the Western Hemisphere." If anyone has any questions,
they can send an e-mail to: [email protected] .
***********************************************************************
TROPICAL CYCLONE NAMES
for the
NORTHWEST PACIFIC
For over a half-century (since at least 1945) the military weather
forecasters, initially members of the U. S. Navy and later also from
the U. S. Air Force, have named tropical cyclones forming in the
Northwest Pacific basin. The names utilized were almost exclusively
English feminine names through 1978, but beginning in 1979 men's names
were used with women's names in an alternating fashion. Also, starting
in 1963 the meteorological service of the Philippines (now known as
PAGASA) began assigning Filipino women's names ending in "ng" to
tropical depressions and cyclones forming in or passing through
PAGASA's area of warning responsibility.
All this ended on 31 December 1999. Beginning on 1 January 2000,
tropical cyclones in the Northwest Pacific basin will be named from
a new and very different list of names. The new names are Asian names
and were contributed by all the nations and territories that are
members of the WMO's Typhoon Committee. The new names will be
allotted to developing tropical storms by the Tokyo Typhoon Centre
of the Japanese Meteorological Agency which is the RSMC for the basin.
These newly selected names have two major differences from the rest
of the world's tropical cyclone name rosters. One, the names by and
large are not personal names. There are a few men's and women's names,
but the majority are names of flowers, animals, birds, trees, or even
foods, etc, while some are descriptive adjectives. Secondly, the names
will not be allotted in alphabetical order, but are arranged by
contributing nation with the countries being alphabetized. Fourteen
nations or territories contributed ten names each for a total of
140 names. The first 42 names on the roster are:
Contributing Nation Names
-----------------------------------------------------------------------
Cambodia Damrey Bopha Kong-rey
China Longwang Wukong Yutu
DPR Korea (North) Kirogi Sonamu Toraji
Hong Kong, China Kai-tak Shanshan Man-yi
Japan Tembin Yagi Usagi
Lao PDR (Laos) Bolaven Xangsane Pabuk
Macau Chanchu Bebinca Wutip
Malaysia Jelawat Rumbia Sepat
Micronesia Ewiniar Soulik Fitow
Philippines Bilis Cimaron Danas
RO Korea (South) Kaemi Chebi Nari
Thailand Prapiroon Durian Vipa
U. S. A. Maria Utor Francisco
Vietnam Saomai Trami Lekima
NOTE: I have recently been informed that PAGASA will continue to
assign Filipino names to tropical depressions and cyclones forming in
or moving into its AOR, but that the new WMO-approved names will also
be included in parentheses following the PAGASA name in warnings.
***********************************************************************
DECEMBER HIGHLIGHTS
--> Western Australia struck by two cyclones--one very intense
--> Tropical oceans in general very quiet--Southwest Indian Ocean
sees first tropical storm of season
***********************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for December: No tropical cyclones
***********************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for December: No tropical cyclones
***********************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for December: 3 tropical depressions
Northwest Pacific Activity for December
---------------------------------------
No tropical storms or typhoons developed in the Northwest Pacific
basin during the last month of 1999. JTWC issued warnings on three
South China Sea depressions during the first half of the month. No
warnings were issued by PAGASA on these systems as they all formed
west of that agency's AOR; and, to the author's knowledge, no special
bulletins were issued on these systems by JMA. The first two
depressions, TD-31W and TD-32W, passed south of Vietnam into the Gulf
of Thailand with TD-31W making it almost as far as the Malay Peninsula,
while TD-33W moved into southern Vietnam. I have received no reports
of damage or casualties resulting from these tropical depressions.
Tracks are included for these systems in the accompanying cyclone
tracks file.
***********************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for December: 1 tropical depression **
** - mentioned by IMD as a tropical depression
North Indian Ocean Activity for December
----------------------------------------
There were no tropical cyclones of gale-force or stronger in the
Bay of Bengal or Arabian Sea during December, but there was a
persistent area of disturbed weather in the southern Bay of Bengal
from around 8-12 Dec for which JTWC issued four Formation Alerts. No
warnings were issued by JTWC, but IMD mentioned this area as a weak
depression for a couple of days, so a short track is included in the
accompanying cyclone tracks file.
***********************************************************************
SOUTH INDIAN OCEAN (SIO) - South Indian Ocean West of Longitude 90E
Activity for December: 1 severe tropical storm
The primary sources of information upon which the narrative is based
are the warnings issued by the TCWC on La Reunion Island, associated
with Meteo France, and which is the RSMC for the South Indian Ocean
basin. However, cyclones in this region are named by the sub-regional
centres on Mauritius and Madagascar with longitude 55E as the dividing
line between their respective areas. La Reunion only advises these
centres regarding the intensity of tropical systems. References to
sustained winds should be understood as meaning a 10-min averaging
period unless otherwise stated. In the accompanying track file
some position comparisons have been made with JTWC's positions, and
warnings from JTWC were used as a source of 1-min avg MSW estimates.
South Indian Ocean Activity for December
----------------------------------------
The first named tropical storm of the season in the South Indian
Ocean basin came alive in late December. Severe Tropical Storm Astride
formed in the west-central South Indian and moved on a generally
westward course which carried it across extreme northern Madagascar and
eventually into Mozambique. The summary for Astride was written by
Patrick Hoareau of Rennes, France, a former resident of Reunion Island
and a great enthusiast for tropical cyclones, especially those of the
Indian Ocean. A very, very special thanks to Patrick for writing the
report on Astride and for providing the track for this storm which is
included in the accompanying cyclone tracks file.
Severe Tropical Storm Astride (TC-03S / SIO #01)
24 December - 3 January
-------------------------------------------------
Whereas tropical cyclone development occured in July 1996, 1997
and 1998 in the South Indian Ocean basin from East Africa to North-
western Australia, 1999 kicked the habit and no off-season cyclone
activity was observed. The whole South Indian Ocean had to wait until
the beginning of December within Perth's AOR for cyclone activity to
begin in earnest with Ilsa and John, the latter generating gusts near
160 kts at its peak. The Southwest Indian (west of 90E) within Meteo
France Reunion's (MFR) AOR had been relatively quiet, with a tropical
disturbance in November which JTWC issued a Formation Alert for but
which failed to organize further. But by the end of the second decade
of December activity was set to kick off with the UKMET model
predicting the inception of a tropical cyclone southeast of Diego
Garcia near Christmas time.
As early as the 24th of Dec visible imagery was clearly depicting
an organising cyclonic circulation southeast of Diego Garcia.
At 0230 UTC JTWC issued a Formation Alert locating the center near
9.5 S, 75.2 E, or about 240 nm southeast of Diego. Maximum 1-min avg
winds were estimated between 20 and 25 kts. Environmental conditions
did appear good for development with low vertical wind shear and good
outflow. The budding system appeared to be under an upper-level ridge
axis and over SSTs near 28-29 C. MFR began issuing warnings on the
disturbance at 1200 UTC, with a Dvorak rating of T2.0 and expecting a
west-southwestward track and some development by the 24-hr forecast
time. Eighteen hours later, at 0600 UTC on 25 Dec, the disturbance
(still at T2.0) had moved westward without significant development.
A SSM/I pass at 0353 UTC depicted very well the LLCC on the eastern
edge of the deep convection near 12.4 S, 70.4 E, or about 325 nm south-
southwest of Diego Garcia. Some low cloud lines were wrapping towards
the center. By afternoon the vertical wind shear had abated
somewhat and the LLCC became more embedded in the deep convection.
By 25/1800 UTC the disturbance had reached T2.5, tropical depression
status by MFR standards, and was still moving westward at 10 kts. SSM/I
data at 1631 UTC located the LLCC near 12.0 S, 68.1 E--about 390 nm
southwest of Diego. During the interim JTWC had already upgraded the
system to T3.0 (1-min avg MSW of 45 kts) at 1200 UTC. Enhanced infra-
red (EIR) imagery depicted tops to -80 C or even colder right over the
center. Continuing to intensify, the depression was upgraded to
moderate tropical storm intensity and named Astride, and by 26/0600 UTC
had 10-min avg winds of 45 kts and was still moving on a westerly
course with MFR expecting a gradual turn to the west-southwest. Six
hours later JTWC upgraded the system to T3.5 (55 kts) while a SSM/I
pass at 1414 UTC located the LLCC near 13.5 S, 64.3 E, or about 315 nm
northeast of St. Brandon.
At 0000 UTC on the 27th, Astride reached severe tropical storm
intensity with 10-min MSW near 50 kts. A SSM/I pass at 0125 UTC helped
to locate the LLCC near 14.4 S, 62.5 E, or about 190 nm northeast of
St. Brandon. An upper-level anticyclone had developed over the tropical
storm and Astride was still forecast by MFR (and JTWC) to strengthen,
slow down its forward motion, and to curve southwestward within a
weakness in the subtropical ridge as a wide, eastward-moving trough
extending up to 25S was expected to be positioned south of the tropical
storm. When visible imagery on the 27th depicted the formation of
an eye, JTWC upgraded the system at 1200 UTC to T4.0 with 1-min avg
maximum sustained winds near 65 kts. MFR's intensity estimate remained
unchanged at T3.5 (50 kts). As a matter of fact EIR imagery at 1200
UTC depicted tops getting significantly warmer. This translated into
a weakening trend and Astride was back at moderate storm intensity at
1800 UTC. The west-southwesterly track was maintained with a
significant slow down and fluctuations as far as the convection's
intensity was concerned near the center. However, at 28/0000 UTC JTWC
kept the intensity unchanged at 65 kts (T4.0). In a previous satellite
bulletin at 1730 UTC, JTWC stated that the Dvorak rating was uncertain
since there were no good features to analyze. The warning went on to
emphasize that some deep convection was developing to the northwest of
the center but was not associated with the tropical storm.
Early on 28 Dec determining the location of the LLCC remained tricky
since convection had built back over it and obscured its position.
Whereas MFR noted the re-development of the convection, the intensity
was lowered to T3.0 (40 kts) while JTWC and KGWC intensity estimates
were still at T4.0 (65 kts)! The intensity of the convection
fluctuated during the 28th. By midday it had weakened again but MFR
expected another flare-up during the following hours. Astride slowly
drifted west-southwestward at about 4 kts and was located about 130 nm
to the northeast of St. Brandon. The weakening trend halted on the 29th
with a 0339 UTC NOAA-15 pass (See Note) clearly highlighting better
organisation. A SSM/I pass at 0445 UTC depicted very well the LLCC
near 15.4 S, 56.3 E, or about 110 nm east of the French island of
Tromelin. Another pass 12 hrs later located the center near 14.9 S,
55.5 E, which is about 80 nm northeast of Tromelin, with both passes
implying a slow west-northwesterly heading. Both MFR and JTWC kept
their intensity estimates steady at T3.0 and T3.5, respectively.
Visible pictures on the 30th located the LLCC just 35 nm north of
Tromelin on the northern edge of the convection. Based on wind
observations from the island, MFR upgraded Astride to severe tropical
storm intensity once again at T3.5 with the 10-min MSW near 50 kts.
Meanwhile, JTWC downgraded the intensity to T3.0. Again, significant
discrepancies for this particular system were observed between the two
agencies. Astride went on to move west-northwestward while weakening
and was downgraded back to moderate tropical storm intensity at 1800
UTC.
By midday on the 31st the weakening storm was located about 30 nm
northeast of Vohemar, Madagascar. Landfall occured between 1800 UTC
and 0000 UTC on 1 Jan 2000 north of Vohemar. At 0000 UTC MFR located
the LLCC over land with an intensity estimate of T2.5 (30 kts 10-min).
Six hours later the LLCC was back over water in the Mozambique Channel.
Whereas Astride continued to weaken further on 1 and 2 Jan, the UKMET
model had been predicitng some re-intensification over the Channel for
many days. Eventually the model got it right (once again?) and Astride
reached tropical depression threshold (T2.5) at 02/1200 UTC about 85 nm
south of the French island of Mayotte (Comoros). MFR was calling for
some further strengthening as Astride continued westward over the
Channel. At 0000 UTC on 3 Jan Astride's center was located about
15 nm east of Mogincual, Mozambique, and was on the verge of making
landfall, still at 30 kts. The intensification process had stopped
and the convection's growth both in intensity and areal extent observed
on the 2nd had come to an end during the night. MFR issued their last
warning on Astride at 03/0600 UTC placing it inland. (Note: JTWC
stopped issuing advisories on the system at 01/1200 UTC. During the
re-intensification process over the Channel their intensity estimate
never reached T2.5 again.
PATRICK'S NOTE: the SSM/I and TRMM passes analyses are of my own making
along with a few other observations. Satellite pictures from both
NOAA-15 and NOAA-14 were provided to the author whenever a tropical
cyclone was west of about 80E by Jean Marc De Maroussem, a great
cyclone enthusiast living in Mauritius at Tamarin, and who not only
owns a weather station (Weather Monitor2 from Davis) but also Prosat
for Windows, which allows him to get polar satellite pitures of the
region as the satellites pass overhead. Again, very warm
acknowledgments to Jean Marc who has been sending me very nice
satellite pictures in real-time of subsequent storms (Babiola, Connie,
and Damienne) along with multiple data when available.
ADDITIONAL NOTE
SOUTHERN HEMISPHERE TROPICAL CYCLONE STATISTICS
-----------------------------------------------
Patrick has spent a great amount of time studying and sifting
through records and tracks of cyclones in the Southern Hemisphere, and
has compiled quite an impressive amount of statistical data on these
storms. Some of this is available at the following URL:
http://australiansevereweather.com/cyclones/stats.htm>
***********************************************************************
AUSTRALIAN REGION (AUG) - From Longitude 90E Eastward to Longitude 160E
Activity for December: 2 tropical LOWs (one likely hybrid)
1 tropical cyclone of storm intensity
1 severe tropical cyclone (hurricane)
The primary sources of information for Australian Region tropical
cyclones are the warnings and bulletins issued by the three TCWC's
at Perth, Darwin, and Brisbane. Information gleaned from JTWC's
warnings is used as a supplement for times when it was impossible to
obtain Australian bulletins and for comparison purposes. References
to sustained winds should be understood as being based on a 10-min
averaging period unless otherwise noted.
Matthew Saxby, a tropical cyclone enthusiast from Queanbeyan, New
South Wales, Australia, typed up the tracks for the cyclones and LOWs
in the Australian Region. Also, Carl Smith, another dedicated tropical
cyclone enthusiast from the Gold Coast of Queensland, authored the
narratives for Tropical Cyclones Ilsa and John plus provided some
information on the late December hybrid Queensland LOW. A very, very
special thanks to Matthew and Carl for their assistance.
NOTE: In his write-up on Tropical Cyclone John, Carl alludes to Blue,
Yellow, and Red alerts. The basic definitions of these alerts are:
BLUE - a cyclone has formed and could impact an area within 36 hrs
YELLOW - the cyclone will likely impact the area within 12 hrs
RED - the cyclone is imminent
A description of the Australian Cyclone Severity Scale can be found in
Chris Landsea's FAQ on HRD's website:
http://www.aoml.noaa.gov/hrd/tcfaq/tcfaqD.html#D2>
or on Michael Bath's Australian Severe Weather site:
http://australiansevereweather.com/cyclones/history.htm>
Also, I performed some editing on Carl's write-ups, especially the one
for Cyclone John. For anyone who is interested in reading his complete
cyclone reports, they are available at the following URLs:
http://www.ace-net.com.au/~carls/IlsaReport.htm>
http://www.ace-net.com.au/~carls/JohnReport.htm>
Australian Region Activity for December
---------------------------------------
During the first week of December, 1999, monsoonal activity was
building in the region to the north of Australia, stretching across
southern Indonesia, far northern Australia, southern Papua New Guinea,
and the Solomon Islands. A small Tropical LOW developed in the Coral
Sea off Cape York Peninsula, resulting in the Brisbane TCWC issuing a
Cyclone Watch for the Cape York area, but the LOW soon weakened and
moved eastward, away from the coast. During the second week of
December, intensifying activity, called a monsoonal burst by the Bureau
of Meteorology (BoM), began to concentrate on the Indonesian end of
this range. From this monsoonal activity, two cyclones were born,
Tropical Cyclone Ilsa (01S) and Tropical Cyclone John (02S), which
had the distinction of being the first two named cyclones in the
Southern Hemisphere for the 1999-2000 season.
The early December Tropical LOW formed on 2 Dec about 175 nm north
of Cooktown or about 150 nm east-southeast of Cape Grenville. The
LOW began to move away from the coast and the final bulletin, issued
at 03/0600 UTC, placed the LOW's center about 225 nm northeast of
Cooktown. A few gales may have briefly been present in association
with the LOW early on 3 Dec. The second unnamed LOW formed in
central Queensland, about 275 nm southwest of Townsville, on 26 Dec
during a period when monsoonal activity was quite strong across most
of northern Australia and central Queensland. The LOW moved into the
Coral Sea near Mackay on the 27th and deepend to 992 mb early on the
28th. Gales up to 45 kts were occurring around this time, but
fortunately for southeastern Queensland, the LOW continued to move
southeastward to eastward away from the coast and eventually into
Wellington's AOR. Gales were experienced on Fraser Island on 28 Dec,
and severe beach erosion occurred on the Sunshine Coast north of
Brisbane and to a lesser extent on the Gold Coast south of Brisbane.
Heavy rains were experienced through southeastern Queensland on the
27th, but skies had cleared by the 29th.
This second LOW was never called a Tropical LOW by the Brisbane
TCWC, and likely was some sort of hybrid system. I took a few looks
at some satellite imagery of the system and it did not look like a
classic tropical cyclone to me. (A considerable portion of the above
information on this system was forwarded to me by Carl Smith, who
lives in one of the areas affected by the LOW.)
Tropical Cyclone Ilsa (TC-01S)
10 - 17 December
-------------------------------
Tropical Cyclone Ilsa formed in the South Indian Ocean to the west
of Christmas Island and northeast of the Cocos Islands, with JTWC
issuing a warning for TC-01S at 2100 UTC on 10 Dec. The system
was tracking east-southeastward at 3 kts, and a 1439 UTC Special
Sensor Microwave Imager (SSM/I) pass and a 1354 UTC Tropical Rainfall
Measurement Mission (TRMM) pass indicated a well-defined LLCC with a
convective band to the north beginning to wrap in towards the centre.
Ilsa was named by the Perth TCWC at around 0200 UTC on the 11th of Dec
when a Tropical Cyclone Watch for a Category 1 cyclone was issued for
Christmas Island.
Ilsa was upgraded to Category 2 status at 12/0400 UTC with a CP of
985 mb and maximum wind gusts of 70 kts when located about 215 nm west-
southwest of Christmas Island and 325 nm east of the Cocos Islands,
moving southeastward at 6 kts. JTWC noted at 2100 UTC on the 11th that
a SSM/I pass depicted deep convection continuing to build in towards
the LLCC specifically from the northeast, and imagery indicated a
convective band developing southeast of the LLCC with synoptic data
showing stronger winds in the northern half. JTWC forecast Ilsa
to track generally southeastward within the mid-level steering flow
of the subtropical ridge extending from northwest Australia.
Ilsa was downgraded to a Category 1 cyclone at 12/1600 UTC with the
CP having risen to 990 mb, whilst JTWC noted at 2100 UTC that animated
imagery depicted persistent deep convection particularly to the north-
east of the LLCC. Satellite imagery revealed improved organisation
of the system over the previous six hours, and enhanced infrared
imagery indicated continued cloud top cooling; also water vapour
imagery continued to show good outflow aloft.
Ilsa made its way south-southeastward, then eastward, passing about
100 nm to the south of Christmas Island, and the Watch for Christmas
Island was soon cancelled. The cyclone continued to move in an
east-northeasterly to easterly direction over the next few days,
with the CP varying between 985 and 990 mb as per the BoM shipping
warnings. Ilsa moved towards the rapidly developing and more dominant
Tropical Cyclone John, which no doubt inhibited further development
due to increasing vertical shear from its outflow.
After Severe Tropical Cyclone John made landfall over northwestern
Australia as a Category 5 cyclone on the morning of 15 Dec and began to
weaken, Ilsa began to move into the area to the north of Western
Australia which was a more favourable environment for development,
thereby causing some concern for communities that had just experienced
Tropical Cyclone John. As John weakened overland, Ilsa slowly
intensified, with northwestern Australian coastal communities being
placed under a Cyclone Watch on the 15th. The cyclone had been
upgraded to Category 2 status when the first Warning was issued at
8:05 am Western Standard Time (0005 UTC) on the 16th for communities
between Cape Leveque and Pardoo. Central pressure was 985 mb with
maximum gusts of 80 kts near the centre, which was moving southeastward
at 13 kts. JTWC noted at 0300 UTC on the 16th that visible satellite
imagery depicted a partially exposed LLCC about 30 nm east of the deep
convection, and that animated satellite imagery showed the deep
convection had decreased in areal extent and was symmetric, with
animated water vapour imagery showing good outflow in the western
quadrant.
During the afternoon Ilsa weakened to a Category 1 cyclone with the
CP increasing to 990 mb and the maximum wind gusts decreasing to
60 kts as it was moving southeastward towards the Eighty-Mile Beach at
16 kts. JTWC noted at 0900 on the 16th that animated visible satellite
imagery revealed the LLCC had become completely exposed with convection
sheared about 70 nm to the west-southwest.
By 16/2200 UTC Ilsa had weakened further to 995 mb with maximum
gusts of 50 kts. JTWC noted in their 2100 UTC warning that animated
satellite imagery showed that the convection had increased in the
previous six hours, and that the LLCC had moved about 20 nm under the
convection. Synoptic data indicated that the winds were symmetrical
around the LLCC and the Port Hedland radar suggested that the
convection was loosely organised and of overall moderate intensity.
Around 0400 UTC on 17 Dec Ilsa crossed the coast on the Eighty-Mile
Beach near the Sandfire Roadhouse on the edge of the Great Sandy
Desert. More than 100 mm of rain was recorded in the Pardoo area and
no further BoM advices were issued. JTWC at 0300 UTC noted that Port
Hedland's radar suggested the convection had decreased in areal extent
and had become poorly organised over the previous six hours. Tropical
Cyclone Ilsa degenerated into a rain depression over the Great Sandy
Desert during the next 12 hours or so. This is a largely uninhabited
area and very few people would have been directly impacted by the
cyclone.
NOTE: Carl has reported the winds in Ilsa in peak gusts in accordance
with the procedure of the Australian TCWC's in their public advices,
which in my opinion, is a very good idea for agencies which report
tropical cyclone winds as a 10-min average since the peak gusts can
exceed the 10-min avg MSW by as much as 40-50%. In terms of the
estimated MSW reported in the High Seas Warnings from Perth and by
JTWC, Ilsa's intensity maintained itself in a sort of steady state for
several days. Peak intensity as per Perth's warnings was reached on
12 Dec when the 10-min avg MSW was estimated at 55 kts (JTWC's 1-min
avg MSW was 45 kts at the time). After weakening slightly, Ilsa
reached a secondary peak on 15 Dec when the 10-min avg MSW was
estimated to have reached 50 kts. JTWC's peak intensity of 60 kts
(1-min avg) was attained also on 15 Dec.
Severe Tropical Cyclone John (TC-02S)
9 - 16 December
--------------------------------------
Tropical Cyclone John was named by the Perth TCWC at 2200 UTC on
12 Dec in the Timor Sea about 315 nm northwest of Broome on the
northwestern coast of Western Australia. According to the JTWC
warning at 2100 UTC, an 1130 UTC Tropical Rainfall Measurement
Mission (TRMM) pass depicted a tightly curved convective band
surrounding a 20 nm-wide cloud-filled eye and deep convection appeared
to be about 25 nm southwest of the LLCC. Water vapour and 200-mb
analyses indicated a developed upper-level anticyclone situated over
the system, and animated imagery revealed feeder bands moving over the
Eighty-Mile Beach, northeast of Port Hedland. Tropical Cyclone John
was forecast to move south-southwestward within the mid-level steering
flow of a subtropical ridge situated over Australia.
Tropical Cyclone John was upgraded to a Category 3 (Australian
Severity Scale) cyclone at 1600 UTC on Sunday, 12 Dec, and the first
PRIORITY media release for broadcast by BoM Perth was issued at 2240
UTC the same day which stated that "a Cyclone Watch is now current for
a Category 3 cyclone for the coastal areas between Wallal and Onslow."
At 2200 UTC the central pressure was 965 mb with maximum wind gusts of
110 kts near the centre. JTWC noted that a previous TRMM image
revealed a well-structured banded eye feature which visible imagery
showed had developed into an elongated full-eye structure, and
satellite imagery showed that the system continued to dominate the
region with good outflow aloft and a symmetric overall appearance.
Advices continued to show that John was intensifying, and was
upgraded to Category 4 status at 1300 UTC on Monday, 13 Dec, with a
CP of 955 mb and maximum wind gusts of 120 kts near the centre. The
ongoing warnings showed the continued strengthening of Tropical Cyclone
John overnight, and during the following morning the warning area
progressively increased. JTWC noted that the eye diameter had grown
to 30 nm surrounded by a concentric eyewall.
Tropical Cyclone John reached Category 5 status at 14/0800 UTC when
it was located 105 nm northwest of Port Hedland and 110 nm north-
northeast of Karratha and moving to the south-southwest at 8 kts.
Central pressure was 915 mb with maximum wind gusts of 155 kts near the
centre. JTWC had noted at 0300 UTC that dry air entrainment was
beginning to wrap into the northwestern quadrant of the system.
The next advices showed the number of communities under Yellow and
Blue alerts increasing, and then several places were under Red alert.
At 1400 UTC BoM began issuing hourly warnings, which is normal
procedure when a large cyclone begins impacting coastal communities.
And JTWC noted at 2100 UTC that John had a 33 nm-diameter eye with good
outflow aloft, and that the radar at Dampier indicated a very strong
eyewall associated with the system. Satellite imagery indicated an
elongation of the system along a northwest-southeast axis, and an area
of dry air south and west of the system remained evident in the water
vapour imagery.
Having spared Karratha from the worst of its fury, Tropical Cyclone
John crossed the coast at 8:00 am (0000 UTC) on Wednesday, 15 Dec near
Whim Creek with very destructive and dangerous winds with estimated
gusts of 155 kts near the cyclone's centre. Central pressure was
915 mb with a Severity Category of 5. By 0100 UTC the central pressure
had risen to 920 mb as John began to slowly weaken as it moved inland
in the Whim Creek area. The eye of the cyclone had completed its
coastal crossing by 0200 UTC and had weakened to a Category 4 cyclone
with a CP of 930 mb and maximum wind gusts of 140 kts near the centre.
Tropical Cyclone John had been downgraded to Category 3 status by
the time of the next warning at 0800 UTC. At 0900 UTC JTWC noted that
animated satellite imagery indicated weakening in the northern quadrant
and elongation to the southeast as the cyclone continued to move inland
and into a higher wind shear environment. However, John maintained a
ragged, cloud-filled eye, though it had been over land for the past
eight hours. Northwestern Australian radar imagery indicated that the
eyewall was collapsing, and dry air entrainment had served to weaken
the convection along the northern boundary of the system.
Subsequent warnings showed the continued weakening trend, with
John having been downgraded to a Category 2 cyclone by 9:00 pm
(1300 UTC). At 15/1500 UTC JTWC issued its final warning which stated
that satellite imagery indicated a rapid weakening of the system
due to dry air entrainment and interaction with land. The storm had by
now lost its eye, and JTWC forecast the weakening John to continue to
track south-southeastward under the steering influence of the mid-level
subtropical ridge to the east and completely dissipate within 12 hours.
By 2200 UTC on the 15th Tropical Cyclone John had been downgraded to a
Category 1 cyclone. The final public advice on the system was issued
at 9:00 am (0100 UTC) on 16 Dec, placing the center about 90 km east-
northeast of Newman and moving east-southeastward at 25 km/hr. Peak
gusts by this time were estimated to be down to about 40 kts.
Fortunately the city of Karratha was spared the worst of John's
fury. There was some minor damage in the area such as holes in roofs,
trees uprooted, downed fences, etc, but apparently nothing major. A
midday radio current affairs program on 16 Dec reported that the mining
town of Newman had recorded 240 mm of rain associated with the storm
at that point. Some roads and about 25 homes in the area were flooded.
By evening the rainfall total in the area had reached 500 mm. At
Point Samson Caravan Park, about 9 or 10 persons rode out the cyclone
in a large refrigerator normally used for storing fish. A lady who
manages a roadhouse at Auski, about 190 km north of Newman, reported
that a number of truck drivers protected the roadhouse from the cyclone
by parking their vehicles in an arc to block the strong winds. (See
Note #1 following the main narrative.)
At Whim Creek, near where the eye of John crossed the coast, the
top floor of a 113-year old pub and hotel was lost. The owner of the
hotel reported that when he looked out during the height of the storm,
he saw sheets of iron flying everywhere. Just how powerful the winds
were was evidenced by a large back hoe which had been parked behind
the pub to afford it some protection. The large tractor was pushed
back about 15 feet (4.6 m) by the winds. Overall, the damage from
this very intense cyclone was relatively light due to the sparseness
of population in the area where the inner core made landfall. Being
one of the more cyclone-prone regions on earth, buildings along the
northwestern coastline of Western Australia are built very sturdily
in order to withstand the fierce tropical cyclones which strike the
area, but even with this high standard of construction, had the intense
inner core of John made landfall near a large population centre like
Karratha, damage would have been severe and widespread and likely some
lives would have been lost.
1st NOTE: In his report on John, Carl gives the following interesting
bit of information regarding the trucks used to block the wind at the
Auski roadhouse: "The arc arrangement of the 'trucks' around a
roadhouse was quite a good innovation to protect the place. To put
this in perspective, most Australians would know that 'trucks' in this
region are 'road trains', which are very heavy duty trucks capable of
pulling many thousands of tonnes and can have up to six full-sized
trailers towed behind them--they are very dangerous vehicles to over-
take. Here, they would probably be carrying very heavy replacement
parts for iron ore mining machinery, so in some cases the load could
be up to 2 or 3 normal traffic lanes wide and so high that they need
to take a route where there are no bridges to go under. Two or three
trailers would be a very large and heavy load, and a number of these
'trucks' would be a very effective wind break that even Tropical
Cyclone John would find very difficult to shift!"
2nd NOTE: Carl has reported the winds in John in peak gusts in
accordance with the procedure of the Australian TCWC's in their public
advices, which in my opinion, is a very good idea for agencies which
report tropical cyclone winds as a 10-min average since the peak gusts
can exceed the 10-min avg MSW by as much as 40-50%. In terms of the
estimated MSW reported in the High Seas Warnings from Perth and by
JTWC, Tropical Cyclone John reached its peak intensity on 14 Dec from
around 1000 UTC until landfall. Perth's 10-min avg MSW was 110 kts
while JTWC's 1-min avg MSW was 130 kts. This represents a very close
agreement in peak intensity between the two warning centres.
***********************************************************************
SOUTHWEST PACIFIC (SWP) - South Pacific Ocean East of Longitude 160E
Activity for December: 2 tropical depressions
NOTE: Most of the information presented below was taken from the
operational warnings and advisories issued by the Fiji TCWC at Nadi.
References to sustained winds imply a 10-minute averaging period
unless otherwise noted. Also, the basic definition of a cyclone in
WMO Region 5 (Australia and the South Pacific) has the unique
requirement that a depression must have gale-force winds more-or-less
completely surrounding the center before the system is named as a
tropical cyclone. Hence, often gales of 35-40 kts may be present in
one or two quadrants but the system is not considered a tropical
cyclone. Last season Fiji initiated their own numbering scheme for
tropical disturbances (01F, 02F, etc) that form in the Nadi AOR.
Some of the numbered disturbances never warrant depression status.
Southwest Pacific Activity for December
---------------------------------------
There were no named tropical cyclones in the South Pacific Ocean
east of 160E in the final month of 1999. There were two systems which
were designated as tropical depressions by the TCWC at Nadi, Fiji--both
during the first few days of the month. The first system, TD-03F,
formed and remained quasi-stationary near the islands of Vanuatu around
1-3 Dec. The second depression, TD-04F, formed on 5 Dec near New
Caledonia and moved fairly quickly in a generally eastward direction,
passing near Matthew and Hunter Islands and well to the south of Fiji,
and had weakened amongst the southern islands of the Kingdom of Tonga
by 7 Dec. Gale warnings were issued for this system in anticipation
of some peripheral gales in the southern quadrant only. Short tracks
are given for these depressions in the accompanying cyclone tracks
file. No warnings were issued by JTWC for either of these systems.
***********************************************************************
EXTRA FEATURE
In order to shorten the amount of typing in preparing the narrative
material, I have been in the habit of freely using abbreviations and
acronyms. I have tried to define most of these with the first usage
in a given summary, but I may have missed one now and then. Most of
these are probably understood by a majority of readers but perhaps a
few aren't clear to some. To remedy this I developed a Glossary of
Abbreviations and Acronyms which I included in the July, 1998 summary.
I will include this glossary from time to time, primarily in "lean"
months without a lot of tropical cyclone activity to cover. But if
anyone missed receiving it and wishes to obtain a copy, send me an
e-mail privately and I'll forward them a copy.
***********************************************************************
AUTHOR'S NOTE: This summary should be considered a very preliminary
overview of the tropical cyclones that occur in each month. The cyclone
tracks (provided separately) will generally be based upon operational
warnings issued by the various tropical cyclone warning centers. The
information contained therein may differ somewhat from the tracking and
intensity information obtained from a "best-track" file which is based
on a detailed post-seasonal analysis of all available data. Information
on where to find official "best-track" files from the various warning
centers will be passed along from time to time.
The track files are not being sent via e-mail. They can be retrieved
in the following manner:
(a) FTP to: hrd-type42.nhc.noaa.gov [140.90.176.206]
(b) Login as: anonymous
(c) For a password use your e-mail address
(d) Go to "data" subdirectory (Type: cd data)
(e) Set file type to ASCII (Type: ascii)
(f) Transfer file (Type: get remote_file_name local_file_name )
(The files will be named with an obvious nomenclature--using
December as an example: dec99.tracks)
(g) To exit FTP, type: quit
Both the summaries and the track files are standard text files
created in DOS editor. Download to disk and use a viewer such as
Notepad or DOS editor to view the files.
The first summary in this series covered the month of October,
1997. If anyone wishes to retrieve any of the previous summaries,
they may be downloaded from the aforementioned FTP site at HRD. The
summary files are catalogued with the nomenclature: dec99.sum, for
example.
Back issues can also be obtained from the following websites
(courtesy of Michael Bath, Michael V. Padua, Tom Berg, Michael
Pitt, and Rich Henning):
http://australiansevereweather.com/cyclones/>
http://www.geocities.com/capecanaveral/6825>
http://www.hcane.com/tropcl.html>
http://www.qisfl.net/home/hurricanemike>
http://www.met.fsu.edu/gsc/Docs/Grads/henning/cyclones/>
Another website where much information about tropical cyclones may
be found is the website for the UK Meteorological Office. Their site
contains a lot of statistical information about tropical cyclones
globally on a monthly basis. The URL is:
http://www.met-office.gov.uk/sec2/sec2cyclone/sec2cyclone.html>
TROPICAL CYCLONE REPORTS AVAILABLE
I have discovered that JTWC now has available on its new website
the complete Annual Tropical Cyclone Report for 1997 (1996-1997 season
for the Southern Hemisphere). Also, tracks only for the 1998 tropical
cyclones are currently available.
The URL is: http://199.10.200.33/jtwc.html>
Also, TPC/NHC has available on its webpage nice "technicolor"
tracking charts for the 1999 Atlantic and Eastern North Pacific
tropical cyclones; also, preliminary storm reports for all the 1999
Atlantic and some of the Eastern North Pacific cyclones are now
available.
The URL is: http://www.nhc.noaa.gov>
Prepared by: Gary Padgett
E-mail: [email protected]
Phone: 334-222-5327 (nights & weekends) / 850-882-2594 (weekdays)
***********************************************************************
***********************************************************************
|
Document: summ9912.htm
Updated: 4th January 2007 |
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