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Tropical Cyclone 201221 : JTWC Advisories
Season 2011-2012 Summaries (Operational Data): [AU] [SIO] [SPAC] [SH]
---> Tropical Cyclone 201221 Track Map and Data

WTPS21 PGTW 20120629 10:00z
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
A 160 NM RADIUS OF 13.2S 154.0E WITHIN THE NEXT 06 TO 24 HOURS.
AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF NUMBERED TROPICAL CYCLONE
WARNINGS AT THIS TIME.  WINDS IN THE AREA ARE ESTIMATED TO BE 25 TO
30 KNOTS. METSAT IMAGERY AT 290930Z INDICATES THAT A CIRCULATION
CENTER IS LOCATED NEAR 11.8S 154.7E.  THE SYSTEM IS MOVING
SOUTHEASTWARD AT 08 KNOTS.
2. REMARKS: THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 11.2S
154.2E, IS NOW NEAR 11.7S 154.7E, APPROXIMATELY 465 NM EAST-SOUTHEAST
OF PORT MORESBY, PAPUA NEW GUINEA. RECENT ANIMATED MULTISPECTRAL
SATELLITE IMAGERY DEPICTS PERSISTENT DEEP CENTRAL CONVECTION OVER A
WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC). ALSO, A 290527Z
AMSU-B MICROWAVE IMAGE SHOWS VERY TIGHT SPIRAL BANDING FEEDING INTO
THE LLCC. A 290142Z SCATTEROMETRY PASS SHOWS 25-30 KNOT WIND BARBS IN
THE LLCC. THE CYCLONE IS CURRENTLY TRACKING ALONG THE SOUTHWEST
PERIPHERY OF A SHALLOW NEAR EQUATORIAL RIDGE. HOWEVER, A LOW- TO
MID-LAYERED SUBTROPICAL RIDGE TO THE SOUTH IS EXPECTED TO ASSUME
STEERING OVER THE NEXT 12-24 HOURS AND DEFLECT THE SYSTEM WESTWARD.
THE VWS WILL SIGNIFICANTLY INCREASE AS THE UPPER LEVEL WINDS BECOME
OUT-OF-PHASE WITH LOW-LEVEL WINDS AND STORM MOTION. IT IS DURING THE
TRANSITION IN THE STEERING THAT THE SYSTEM MAY REACH WARNING
CRITERIA, HOWEVER BRIEF, BEFORE THE STRONG VWS DISSIPATES IT. MAXIMUM
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA
LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1005 MB. THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS IS UPGRADED TO HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
301000Z.  //
=========================================================================
WTPS31 PGTW 20120629 15:00z
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 21P (TWENTYONE) WARNING NR 001//
RMKS/
1. TROPICAL CYCLONE 21P (TWENTYONE) WARNING NR 001
   01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
   WARNING POSITION:
   291200Z --- NEAR 12.2S 154.8E
     MOVEMENT PAST SIX HOURS - 165 DEGREES AT 04 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   REPEAT POSIT: 12.2S 154.8E
    ---
   FORECASTS:
   12 HRS, VALID AT:
   300000Z --- 12.6S 154.8E
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   RADIUS OF 034 KT WINDS - 030 NM NORTHEAST QUADRANT
                            035 NM SOUTHEAST QUADRANT
                            030 NM SOUTHWEST QUADRANT
                            030 NM NORTHWEST QUADRANT
   VECTOR TO 24 HR POSIT: 225 DEG/ 03 KTS
    ---
   24 HRS, VALID AT:
   301200Z --- 13.1S 154.3E
   MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
   VECTOR TO 36 HR POSIT: 245 DEG/ 07 KTS
    ---
   36 HRS, VALID AT:
   010000Z --- 13.7S 152.9E
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
    ---
REMARKS:
291500Z POSITION NEAR 12.3S 154.8E.
TROPICAL CYCLONE 21P, LOCATED APPROXIMATELY 475 NM EAST-SOUTHEAST OF
PORT MORESBY, PAPUA NEW GUINEA, HAS TRACKED SOUTH-SOUTHEASTWARD AT 04
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS THE COLD DENSE OVERCAST HAS COOLED AS THE CYCLONE
SLOWED ITS FORWARD MOTION. THE INITIAL POSITION WAS EXTRAPOLATED FROM
A 290816Z TRMM MICROWAVE IMAGE WITH POOR CONFIDENCE. THE INITIAL
INTENSITY WAS BASED ON THE DVORAK ESTIMATE FROM PGTW AND FROM A
291057Z ASCAT PASS THAT SHOWS 25-30 KNOT WIND BARBS FEEDING INTO THE
LOW LEVEL CIRCULATION CENTER. UPPER LEVEL ANALYSIS INDICATES THE
CYCLONE IS TRACKING ALONG THE SOUTHWEST PERIPHERY OF A SHALLOW NEAR
EQUATORIAL RIDGE. HOWEVER, A LOW- TO MID-LAYERED SUBTROPICAL RIDGE TO
THE SOUTH IS EXPECTED TO ASSUME STEERING OVER THE NEXT 12-24 HOURS
AND DEFLECT THE SYSTEM WESTWARD. THE VERTICAL WIND SHEAR (VWS) WILL
SIGNIFICANTLY INCREASE AS THE UPPER LEVEL WINDS BECOME OUT-OF-PHASE
WITH LOW-LEVEL WINDS AND STORM MOTION. DURING THE TRANSITION IN THE
STEERING PATTERN, THE SYSTEM MAY SLIGHTLY INTENSIFY BEFORE THE STRONG
VWS DISSIPATES IT BY TAU 36. THE AVAILABLE NUMERICAL GUIDANCE IS
WIDELY SPREAD, THEREFORE, THERE IS POOR CONFIDENCE IN THE TRACK
FORECAST. THIS WARNING SUPERSEDES AND CANCELS REF A, JOINT TYPHOON
WRNCEN PEARL HARBOR HI 291000Z JUN 12 TROPICAL CYCLONE FORMATION
ALERT (WTPS21 PGTW 291000) MAXIMUM SIGNIFICANT WAVE HEIGHT AT 291200Z
IS 11 FEET. NEXT WARNINGS AT 300300Z AND 301500Z.    //
=========================================================================
WTPS31 PGTW 20120630 03:00z
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 21P (TWENTYONE) WARNING NR 002//
RMKS/
1. TROPICAL CYCLONE 21P (TWENTYONE) WARNING NR 002
   01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
   WARNING POSITION:
   300000Z --- NEAR 11.0S 154.8E
     MOVEMENT PAST SIX HOURS - 335 DEGREES AT 04 KTS
     POSITION ACCURATE TO WITHIN 030 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
   REPEAT POSIT: 11.0S 154.8E
    ---
   FORECASTS:
   12 HRS, VALID AT:
   301200Z --- 10.6S 154.4E
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
    ---
REMARKS:
300300Z POSITION NEAR 10.9S 154.7E.
TROPICAL CYCLONE (TC) 21P, LOCATED APPROXIMATELY 320 NM WEST-
SOUTHWEST OF HONIARA, SOLOMON ISLANDS, HAS TRACKED NORTH-
NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY-EXPOSED,
WEAKENING LOW-LEVEL CIRCULATION CENTER (LLCC) WITH RAPIDLY
DECAYING DEEP CONVECTION SHEARED SOUTHEAST OF THE SYSTEM
A 292323Z ASCAT IMAGE INDICATES NUMEROUS 20-25 KNOT
WINDS WITH AN ISOLATED 30 KNOT WIND OVER THE WEST QUADRANT.
THE ASCAT DATA AS WELL AS THE LATEST DVORAK ESTIMATES OF
25-30 KNOTS FROM PGTW AND KNES SUPPORT THE INITIAL INTENSITY
ASSESSMENT OF 30 KNOTS. MSI AND MICROWAVE IMAGERY SHOW THAT
THE LOW-LEVEL CIRCULATION CENTER (LLCC) DECOUPLED FROM THE
DEEP CONVECTION APPROXIMATELY 12 HOURS AGO AND BEGAN TO
TRACK EQUATORWARD UNDER THE STEERING INFLUENCE OF THE LOW-
LEVEL SOUTHERLY FLOW ASSOCIATED WITH THE STRENGTHENING
SUBTROPICAL RIDGE POSITION OVER THE CORAL SEA. THIS IS THE
FINAL WARNING ON THIS SYSTEM BY THE JOINT TYPHOON WRNCEN
PEARL HARBOR HI. THE SYSTEM WILL BE CLOSELY MONITORED FOR
SIGNS OF REGENERATION. MAXIMUM SIGNIFICANT WAVE HEIGHT AT
300000Z IS 10 FEET.//

Tropical cyclone tracks developed by Michael Bath using operational warnings and advisories.


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Document: tropical_cyclone_201221_jtwc_advisories.htm Updated: 2 May 2017