WDPN32 PGTW 070300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (ATSANI) WARNING NR 
035//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 23W (ATSANI), LOCATED APPROXIMATELY 289 NM 
EAST OF HONG KONG, CHINA, HAS TRACKED NORTHWESTWARD AT 05 KNOTS OVER 
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS 
A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH RAPIDLY 
DECAYING DEEP CONVECTION OVER THE NORTHERN SEMICIRCLE. HOWEVER, 
RADAR IMAGERY AND A 062254Z SSMIS COLOR COMPOSITE MICROWAVE IMAGE 
REVEAL TIGHTLY-CURVED BANDING WRAPPING INTO A WELL-DEFINED CENTER, 
WHICH SUPPORTS THE INITIAL POSITION WITH GOOD CONFIDENCE. THE 
INITIAL INTENSITY IS ASSESSED AT 50 KNOTS, HEDGED SLIGHTLY ABOVE THE 
DVORAK CURRENT INTENSITY ESTIMATES OF 3.0 (45 KNOTS) FROM PGTW AND 
KNES. MODERATE (20 KT) VERTICAL WIND SHEAR (VWS), WARM (26 CELSIUS) 
SEA SURFACE TEMPERATURES (SST), AND ENHANCED POLEWARD OUTFLOW ARE 
CONTRIBUTING TO AN OVERALL MARGINAL ENVIRONMENT AS TS 23W TRACKS 
SLOWLY ALONG THE SOUTHWESTERN PERIPHERY OF A WEAK SUBTROPICAL 
RIDGE (STR) POSITIONED TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 23W IS EXPECTED TO TURN SHARPLY SOUTHWESTWARD AFTER TAU 06 
AS LOW-LEVEL RIDGING ASSOCIATED WITH A NORTHEAST SURGE EVENT 
STRENGTHENS OVER THE EAST CHINA SEA. THE SYSTEM IS FORECAST TO 
ACCELERATE SOUTHWESTWARD AND TO WEAKEN STEADILY THROUGH THE 
FORECAST PERIOD AS VWS INCREASES TO 30-40 KNOTS WITH COOLER SST 
VALUES (24-26C). TS 23W SHOULD DISSIPATE BY TAU 48 BUT PERHAPS 
SOONER AS THE ENVIRONMENT QUICKLY DEGRADES. NUMERICAL MODEL GUIDANCE 
IS NOW IN POOR AGREEMENT WITH MAJOR DIFFERENCES IN THE SHORT-TERM 
TRACK AND TIMING OF DISSIPATION. OVERALL, THERE IS LOW CONFIDENCE IN 
THE JTWC FORECAST TRACK.//
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