WDPN32 PGTW 061500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (ATSANI) WARNING NR 
033//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 23W (ATSANI), LOCATED APPROXIMATELY 203 NM 
SOUTH-SOUTHWEST OF TAIPEI, TAIWAN, HAS TRACKED NORTHWESTWARD AT 08 
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED 
(EIR) SATELLITE IMAGERY AND RADAR IMAGERY SHOW TIGHTLY-CURVED 
BANDING WRAPPING INTO A LOW LEVEL CIRCULATION CENTER (LLCC). THE EIR 
IMAGERY FURTHER DEPICTS FLARING DEEP CONVECTION OBSCURING THE LLCC. 
BASED ON THE EIR AND RADAR IMAGERY, THERE IS GOOD CONFIDENCE IN THE 
INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED AT 45 KTS WITH 
GOOD CONFIDENCE BASED ON A 061054Z SATCON ESTIMATE OF 45 KTS, A 
CIMSS ADVANCED DVORAK TECHNIQUE ESTIMATE OF T2.7 (39 KTS), AND 
PGTW/RJTD DVORAK CURRENT INTENSITY ESTIMATES OF T3.0 (45 KTS). LOW 
(10-15 KT) VERTICAL WIND SHEAR (VWS), WARM (27-28 CELSIUS) 
SEA SURFACE TEMPERATURES (SST), AND POLEWARD OUTFLOW ARE 
CONTRIBUTING TO AN OVERALL FAVORABLE ENVIRONMENT AS TS 23W TRACKS 
ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) 
POSITIONED TO THE NORTHEAST. 
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 23W IS EXPECTED TO CONTINUE TRACKING WEST-NORTHWESTWARD 
ALONG THE AFOREMENTIONED STR THROUGH TAU 12, MAINTAINING INTENSITY 
DUE TO FAVORABLE ENVIRONMENTAL CONDITIONS. AFTERWARDS, A STR 
POSITIONED OVER CENTRAL CHINA SHOULD TAKE OVER AS THE PRIMARY 
STEERING MECHANISM AND TURN TS 23W TO A WEST-SOUTHWESTWARD TRACK 
ALONG ITS SOUTHERN PERIPHERY. ON THIS TRACK, THE SYSTEM WILL BEGIN 
TO WEAKEN AS IT ENCOUNTERS INCREASING VWS (20-30 KTS) AND COOLING 
SST, STEADILY WEAKENING UNTIL DISSIPATION AROUND TAU 72, IF NOT 
SOONER. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT. THE NAVGEM 
SOLUTION MAINTAINS A WESTWARD TRACK AFTER TAU 12, HOWEVER, THE GFS 
SOLUTION HAS COME INTO GOOD AGREEMENT WITH THE SOUTHWESTWARD TRACK 
SHOWN BY THE MAJORITY OF MODELS. OVERALL, THERE IS FAIR CONFIDENCE 
IN THE JTWC FORECAST TRACK WHICH IS POSITIONED NEAR THE MULTI-MODEL 
CONSENSUS.//
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