WDXS32 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 10S (SEAN) WARNING NR 
018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.9S 107.0E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 511 NM SOUTHWEST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
EXPOSED AND EXTREMELY SMALL LOW LEVEL CIRCULATION CENTER (LLCC).
THE MSI ALSO SHOWS A LARGE STRATOCUMULUS FIELD TO THE WEST OF THE
LLCC, INDICATIVE OF THE DRY AND STABLE AIR MASS MOVING IN ON THE
SYSTEM FROM THE WEST. ANIMATED WATER VAPOR IMAGERY INDICATES THAT
ROBUST POLEWARD OUTFLOW CONTINUES TO POUR SOUTHEASTWARD FROM THE
CENTER, BUT AS THE VORTEX IS LIMITED TO JUST 500MB AND THERE IS NO
SIGNIFICANT CONVECTION ASSOCIATED WITH THE SYSTEM ANY LONGER, THE
OUTFLOW CHANNEL IS NOT MUCH OF A FACTOR. THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC IN THE MSI.
THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, USING A
BLEND OF THE AVAILABLE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES
OUTLINED ABOVE. THE ENVIRONMENT IS NOW HIGHLY UNFAVORABLE, WITH
HIGH WESTERLY WIND SHEAR, VERY COOL SSTS, AND EXTREMELY DRY AIR
SMOTHERING THE SYSTEM ABOVE ABOUT 600MB.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: THE SYSTEM IS AT THE SUBTROPICAL RIDGE
(STR) AXIS AND IS NEARLY QUASI-STATIONARY. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T3.5 - 55 KTS
   APRF: T2.5 - 35 KTS
   CIMSS SATCON: 58 KTS AT 220600Z
   CIMSS ADT: 33 KTS AT 220530Z
   CIMSS AIDT: 41 KTS AT 220600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 20-25 KTS
   SST: 22-23 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: EXTREMELY DRY MID-LEVEL AIR OVER THE MAJORITY OF
THE CIRCULATION. 

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 NOW SITTING AT THE SUBTROPICAL RIDGE
AXIS, WITH FORWARD MOTION EFFECTIVELY COMING TO A HALT OVER THE
LAST HOUR OR TWO. IT IS ANTICIPATED HOWEVER THAT THE SYSTEM WILL
IN SHORT ORDER BEGIN TO TURN TO THE SOUTHEAST AND ACCELERATE AFTER
IT MOVES SOUTH OF THE RIDGE AXIS. THE SYSTEM WILL THEN CONTINUE TO
TRACK SOUTHEASTWARD THROUGH THE REMAINDER OF THE FORECAST PERIOD.
TC 10S IS NOW OVER VERY COOL WATERS, AND THE LATEST FSU PHASE
SPACE DIAGRAMS, AND MANUAL TC PHASE CLASSIFICATIONS SUGGEST THAT IT
IS A BORDERLINE TROPICAL-SUBTROPICAL SYSTEM AT THIS POINT. HOWEVER,
DUE TO THE HIGHLY UNFAVORABLE CONDITIONS, THE SYSTEM IS ALSO
STEADILY WEAKENING, THOUGH AT THIS POINT THE PACE IS RELATIVELY
SLOW DUE TO MOMENTUM CONSERVATION. SO WHILE THE SYSTEM IS
UNDERGOING SUBTROPICAL TRANSITION (STT), IT IS LIKELY TO DISSIPATE
BELOW WARNING CRITERIA PRIOR TO COMPLETION OF STT, AND THEN WILL
RAPIDLY TRANSITION TO AN EXTRATROPICAL LOW SHORTLY AFTER THE END OF
THE FORECAST PERIOD. THUS THE FORECAST CALLS FOR DISSIPATION,
THOUGH IN REALITY BOTH PROCESSES WILL BE OCCURRING SIMULTANEOUSLY. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN STRONG
AGREEMENT, THOUGH BOTH THE GFS AND GEFS ENSEMBLE MEAN MOVE THE
SYSTEM TO THE SOUTHEAST AT A FASTER CLIP THAN THE REMAINDER OF THE
CONSENSUS MEMBERS, LEADING TO A FAIR AMOUNT OF ALONG-TRACK SPREAD
BY THE END OF THE FORECAST. THE JTWC FORECAST IS LAID CLOSE TO THE
CONSENSUS MEAN WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS ALSO IN
SRONG AGREEMENT, WITH MINIMAL SPREAD IN ACROSS THE INDIVIDUAL
MEMBERS OF THE CONSENSUS, LENDING HIGH CONFIDENCE TO THE JTWC
FORECAST INTENSITY. 

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