WDPN31 PGTW 031500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 04W (CHOI-WAN) 
WARNING NR 020//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 04W (CHOI-WAN), LOCATED APPROXIMATELY 289NM NORTH-
NORTHWEST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWARD AT 11 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY (EIR) SHOWS A NEAR FULLY-EXPOSED LOW-LEVEL CIRCULATION (LLC) 
WITH BROAD CENTRAL CONVECTION REMAINING OFFSET TO THE SOUTHWEST. THE 
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE USING THE EIR LOOP 
AND EXTRAPOLATION OF A 031053Z SSMIS 91GHZ IMAGE. THE INITIAL 
INTENSITY OF 35KTS IS SET WITH FAIR CONFIDENCE BASED ON AN OVERALL 
ASSESSMENT OF MULTIPLE AGENCY DVORAK ESTIMATES OF T2.5/35KTS 
(PGTW/RJTD), T3.0/45KTS (ADT), AND SATELLITE CONSENSUS (SATCON) OF 
43KTS, REFLECTING THE CONTINUED DEEPENING STATE AS THE SYSTEM IS 
BEGINNING TO ROUND THE RIDGE AXIS. THE SYSTEM RESIDES IN A MARGINAL 
ENVIRONMENT WITH GOOD EASTERLY AND EQUATORWARD OUTFLOW, VERY WARM 
(30-31C) SEA SURFACE TEMPERATURES, WHICH ARE OFFSET BY MODERATE TO 
STRONG (25-30KT) VERTICAL WIND SHEAR FROM THE NORTHEAST. 
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE 
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 04W WILL TRACK NORTHEASTWARD UNDER THE STEERING INFLUENCE 
OF THE STR. THE SYSTEM WILL REMAIN AT 35KTS AS IT ROUNDS THE RIDGE 
AXIS THROUGH THE NEXT 24 HOURS. BY TAU 36, TS 04W WILL WEAKEN TO 
30KTS DUE TO INCREASING VWS AND LAND INTERACTION FROM THE RUGGED 
TERRAIN OF TAIWAN. THE SYSTEM WILL REMAIN AT 30KTS AS IT PASSES 
NORTH OF KADENA AIR BASE BY TAU 48, AS IT CONTINUES TRACKING 
NORTHEASTWARD. CONCURRENTLY AT TAU 48, TS 04W WILL UNDERGO EXTRA-
TROPICAL TRANSITION (ETT) AS IT ENTERS THE BAROCLINIC ZONE AND WILL 
COMPLETE ETT EAST OF THE RYUKU ISLANDS, JUST SOUTH OF HONSHU, BY TAU 
72. THERE REMAINS A DISTINCT POSSIBILITY THAT TS 04W WILL DISSIPATE 
BEFORE TAU 72. THE FORECAST TRACK IS LAID SLIGHTLY TO THE RIGHT OF A 
TIGHT MODEL CONSENSUS, OFFSETTING NAVGEM, THE LEFT OUTLIER WITH A 
NORTHWARD TRACK TOWARD THE TAIWAN STRAIT, LENDING OVERALL HIGH 
CONFIDENCE TO THE EXTENDED PORTION OF THE JTWC TRACK FORECAST.//
NNNN