Tropical Storm CHOI-WAN Advisory Paz, 04.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (CHOI-WAN) WARNING
NR 06//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 23W (CHOI-WAN), LOCATED APPROXIMATELY 238 NM
WEST OF WAKE ISLAND, HAS TRACKED WEST-NORTHWESTWARD AT 09 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
CONTINUES TO SHOW DEEP CONVECTIVE BANDING WRAPPING INTO THE
CENTROID. A 031619Z SSMI MICROWAVE IMAGE REVEALS THE BULK OF THE
DEEP CONVECTION ARE OVER THE NORTHEAST AND SOUTHWEST QUADRANTS. DUE
TO MULTIPLE MESOVORTICES ROTATING CYCLONICALLY ABOUT THE CENTROID,
THE CURRENT POSITION IS BASED ON THE EIR LOOP AND SATELLITE FIXES
FROM PGTW AND RJTD WITH LOW CONFIDENCE. THE SYSTEM HAS SLOWED DOWN
OVER THE PAST SIX HOURS INDICATING POSSIBLE CONSOLIDATION. ALTHOUGH
TS 23W IS STILL A VERY LARGE SYSTEM, IT IS GAINING CHARACTERISTICS
TYPICAL OF A TROPICAL STORM, I.E., MORE CENTRALIZED DEEP CONVECTION
AND A CONTRACTING WIND FIELD. THE INITIAL INTENSITY OF 40 KNOTS IS
BASED ON RECENT ASCAT DATA AND CURRENT STRUCTURE. UPPER-LEVEL
ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH GOOD OUTFLOW AND LOW
VWS. ADDITIONALLY, WARM SSTS ARE CONDUCIVE FOR DEVELOPMENT. TS 23W
IS TRACKING ALONG THE SOUTHERN PERIPHERY OF THE STR TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
   B. TS 23W WILL CONTINUE TRACKING WESTWARD UNDER THE INFLUENCE OF
THE STR. FAVORABLE ENVIRONMENTAL CONDITIONS WILL PERSIST; HOWEVER,
DUE TO THE BROAD NATURE OF THE SYSTEM, TS 23W IS EXPECTED TO
GRADUALLY INTENSIFY, LEADING TO A PEAK INTENSITY OF 85 KNOTS BY TAU
72.
   C. IN THE EXTENDED TAUS, TS CHOI-WAN WILL BEGIN TO ROUND THE STR
AND TRACK MORE POLEWARD. AS IT GAINS LATITUDE, VWS WILL INCREASE AND
SSTS WILL DECREASE, RESULTING IN GRADUAL THEN RAPID WEAKENING.
CONCURRENTLY, TS 23W WILL COMMENCE EXTRA-TROPICAL TRANSITION AS IT
ENTERS THE COLD BAROCLINIC ZONE. THE CYCLONE WILL TRANSFORM INTO A
COLD CORE LOW BY TAU 120. AVAILABLE MODEL GUIDANCE IS IN GOOD
AGREEMENT, HOWEVER, GIVEN THE UNCERTAINTY IN THE CURRENT STORM
MOTION AND THE INITIAL PORTION OF THE FORECAST TRACK, THERE IS LOW
CONFIDENCE IN THE JTWC FORECAST TRACK.//
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