WDPN32 PGTW 050300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (CHOI-WAN) WARNING 
NR 11//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 23W (CHOI-WAN), LOCATED APPROXIMATELY 725 NM
NORTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED WESTWARD AT 13 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
(MSI) DEPICTS TIGHTLY-CURVED BANDS OVER THE NORTHERN AND SOUTHERN 
SEMI-CIRCLE WRAPPING INTO THE CONSOLIDATED LOW-LEVEL CIRCULATION 
CENTER. THE CURRENT POSITION IS BASED ON THE MSI AND SATELLITE FIXES 
FROM PGTW AND RJTD WITH FAIR CONFIDENCE. THE INITIAL INTENSITY OF 55 
KNOTS IS BASED ON THE CURRENT STRUCTURE AND A RECENT 042305Z ASCAT 
IMAGE. UPPER-LEVEL ANALYSIS CONTINUES TO INDICATE TS 23W IS LOCATED 
IN A FAVORABLE ENVIRONMENT WITH RADIAL OUTFLOW AND LOW VERTICAL WIND 
SHEAR (VWS). ADDITIONALLY, WARM SEA SURFACE TEMPERATURES (SSTS) ARE 
CONDUCIVE FOR FURTHER DEVELOPMENT. TS 23W IS TRACKING ALONG THE 
SOUTHERN PERIPHERY OF A DEEP-LAYERED SUB-TROPICAL RIDGE (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 OVER THE NEXT 12 TO 18 HOURS. AFTERWARDS, TS CHOI-WAN IS 
FORECAST TO ROUND THE STR AND TRACK MORE POLEWARD. FAVORABLE 
ENVIRONMENTAL CONDITIONS WILL PERSIST OVER THE NEXT 48 HOURS; 
HOWEVER, DUE TO THE BROAD NATURE OF THE SYSTEM, TS 23W IS EXPECTED 
TO GRADUALLY INTENSIFY AS IT CONTINUES TO CONSOLIDATE. AS THE SYSTEM 
GAINS LATITUDE, IT WILL ENCOUNTER INCREASING VWS AND DECREASING SSTS 
WHICH WILL BEGIN TO WEAKEN THE SYSTEM.
   C. CONTINUED UNFAVORABLE CONDITIONS WILL FURTHER DECAY THE 
SYSTEM. BY TAU 72, TS CHOI-WAN WILL BEGIN EXTRA-TROPICAL TRANSITION 
AS IT INTERACTS WITH THE MIDLATITUDE WESTERLIES. TS 23W WILL BE 
FULLY EMBEDDED IN THE BAROCLINIC ZONE, GAINING FRONTAL 
CHARACTERISTICS, AND TRANSITIONING TO A STRONG COLD-CORE LOW BY THE 
END OF THE FORECAST PERIOD. AVAILABLE MODEL GUIDANCE REMAINS IN GOOD 
AGREEMENT; HOWEVER, GIVEN THE UNCERTAINTY IN THE INITIAL POSITION 
AND THE CURRENT STORM MOTION, THE JTWC FORECAST TRACK CONFIDENCE 
LEVEL REMAINS LOW.//
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