WDPN31 PGTW 050300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (CHOI-WAN) 
WARNING NR 026//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 04W (CHOI-WAN), LOCATED APPROXIMATELY 237 NM 
WEST-SOUTHWEST OF KADENA AB, HAS TRACKED NORTHEASTWARD AT 20 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
DEPICTS AN ELONGATED CIRCULATION UNDER DEEP CONVECTION ASSOCIATED 
WITH THE MEI-YU BOUNDRY, WHICH IS POSITIONED NORTHWEST OF THE RYUKYU 
ISLANDS. THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED 
ON ANALYSIS OF COMPOSITE RADAR LOOPS. THE INITIAL INTENSITY OF 35 
KTS IS HEDGED SLIGHTLY HIGHER THAN AN ADVANCED DVORAK TECHNIQUE 
INTENSITY ESTIMATE OF T2.2 (32 KTS) AND IS SUPPORTED BY A SURFACE 
WIND OBSERVATION OF 31 KTS AT 050000Z AT ISHIGAKIJIMA. TS CHOI-WAN 
IS TRACKING ALONG THE NORTHWESTERN PERIPHERY OF A SUB-TROPICAL RIDGE 
(STR) POSITIONED TO THE SOUTHEAST AND THROUGH A MARGINALLY 
UNFAVORABLE ENVIRONMENT WITH WARM (28-29 CELSIUS) SEA SURFACE 
TEMPERATURES (SSTS) OFFSET BY MODERATE (15-25 KTS) VERTICAL WIND 
SHEAR (VWS) AND CONVERGENT WESTERLY FLOW IN THE UPPER LEVELS. 
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE 
PREVIOUS PROGNOSTIC REASONING MESSAGE.   
   B. TS CHOI-WAN WILL CONTINUE TO TRACK GENERALLY NORTHEASTWARD 
ALONG MEI-YU BOUNDARY. AROUND TAU 12, AS THE SYSTEM FURTHER 
INTERACTS WITH THE BOUNDARY, THERE IS POTENTIAL FOR 35+ KTS WINDS 
DUE TO THE ADDED VORTICITY IMPARTED BY THE NORTHEASTERLY FLOW. AFTER 
TAU 12, VWS WILL INCREASE DRAMATICALLY TO 40+ KTS AND SSTS WILL 
DECREASE TO 24-25 CELSIUS, LEADING TO A DECREASING TREND IN 
INTENSITY. TS CHOI-WAN WILL CONTINUE IT'S NORTHEASTWARD TRACK AS IT 
GETS EMBEDDED IN THE WESTERLIES AND DISSIPATES OVER WATER BY TAU 36. 
NUMERICAL MODEL SOLUTIONS ARE IN GOOD AGREEMENT REGARDING STORM 
TRACK LEADING TO OVERALL HIGH CONFIDENCE IN THE JTWC FORECAST TRACK, 
WHICH IS PLACED ALONG THE MULTI-MODEL CONSENSUS.//
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