WDXS32 PGTW 222100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 10S (SEAN) WARNING NR 
020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.4S 107.5E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 512 NM SOUTHWEST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 10S (SEAN) WITH A COMPLETELY EXPOSED AND SHALLOW LOW-LEVEL
CIRCULATION CENTER (LLCC). REMNANT CONVECTION CAN BE SEEN DRIFTING
POLEWARD, PULLED BY A BRANCH OF THE UPPER-LEVEL JET. THE ENVIRONMENT 
CONTINUES TO BE HIGHLY UNFAVORABLE DUE TO THE HIGH VERTICAL WIND SHEAR 
(VWS), COOL SEA SURFACE TEMPERATURES (SST), AND SIGNIFICANT DRY AIR 
ENTRAINMENT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED 
ON THE EXPOSED LLCC IN THE ANIMATED EIR IMAGERY. THE INITIAL INTENSITY 
OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A NARROW BAND OF 
50-55 KTS VISIBLE ON THE 221116Z SAR PASS, CONTINUOUS WEAKENING TREND, 
AS WELL AS CURRENT CIMSS MICROWAVE SOUNDERS INTENSITY ASSESSMENT OF 40 
KTS. DVORAK ESTIMATES ARE TOO LOW, DUE TO LACK OF CONVECTION 
ASSOCIATED WITH THE REMAINING CIRCULATION.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA AND SAR DATA 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) POSITIONED TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS SATCON: 34 KTS AT 221900Z
   CIMSS ADT: 25 KTS AT 221900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 25-30 KTS
   SST: 23-24 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TC 10S IS FORECAST TO TRAVEL ALONG THE
SOUTHWESTERN PERIPHERY OF THE STR ON A SOUTH-SOUTHEASTERLY TRACK,
WHILE CONTINUING TO WEAKEN, DRIVEN BY HIGHLY UNFAVORABLE ENVIRONMENTAL 
CONDITIONS. DESPITE RELATIVELY SLOW SPEED OVER WATER, SIGNIFICANT VWS 
OF NEARLY 30 KTS IS PUSHING ANY REMAINING CONVECTION FURTHER POLEWARD, 
WHILE THE SYSTEM CONTINUES TO UNDERGO A SUBTROPICAL TRANSITION (STT), 
AS INDICATED BY THE FSU CYCLONE PHASE DIAGRAM. VWS IS EXPECTED TO ONLY 
INCREASE, ALONG WITH DRY AIR CONTINUING TO ERODE THE VORTEX, TC 10S IS 
FORECAST TO DISSIPATE WITHIN THE NEXT 24 HOURS, BEFORE IT COMPLETES 
THE STT.

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE IS IN GOOD
AGREEMENT THROUGHOUT THE FORECAST PERIOD, WITH THE CROSS-TRACK
SPREAD OF 85NM. THE JTWC FORECAST IS LAID CLOSE TO THE MULTI-MODEL
CONSENSUS, OFFSETTING THE ONLY OUTLYING GUIDANCE FROM NAVGEM, WHICH
PREDICTS A MORE SOUTHERLY INITIAL TRACK. INTENSITY GUIDANCE IS ALSO
IN GOOD AGREEMENT, WITH ALL MEMBERS INDICATING STEADY WEAKENING.
THEREFORE, THE JTWC FORECAST IS ASSESSED TO REACH BELOW WARNING
LEVELS BY THE END OF THE FORECAST PERIOD.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: HIGH//
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