WDPN31 PGTW 230300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (VICENTE) WARNING 
NR 10//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 09W (VICENTE), LOCATED APPROXIMATELY 150 NM SOUTH-
SOUTHEAST OF HONG KONG, HAS TRACKED NORTH-NORTHWESTWARD AT 06 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
SHOWS THE PERSISTENT DEEP CENTRAL CONVECTION SHEARING OFF TO THE 
EAST OF THE LOW-LEVEL CIRCULATION CENTER (LLCC) WITH MULTIPLE 
FEEDER BANDS ALONG THE PERIPHERIES. THE CURRENT POSITION IS BASED 
ON A 222249Z SSMIS 37 GHZ IMAGE WITH HIGH CONFIDENCE. STORM MOTION 
OVER THE PAST 12 HOURS UNEXPECTANTLY RETROGRADED TO THE NORTHEAST 
BUT RECENTLY HAS TAKEN A MORE NORTH-NORTHWESTWARD TRAJECTORY. IT 
SEEMS THAT A MESO-SCALE UPPER-LEVEL CYCLONE EXISTS OVER THE LLCC 
WHICH IS CAUSING CONVERGENCE AND WIND SHEAR ALONG THE WESTERN SEMI-
CIRCLE. IT IS SURMISED THAT THIS UPPER-LEVEL CYCLONE, AND 
SOUTHWESTERLY FLOW, HAS MOMENTARILY WEAKENED THE SUBTROPICAL RIDGE 
(STR) THAT HAS BEEN STEERING THE SYSTEM. HOWEVER, DUE TO RECENT 
STORM MOTION THERE IS STILL HIGH CONFIDENCE IN THE OVERALL FORECAST 
PATH TO THE NORTH-NORTHWEST. THE SOUNDING FROM KINGS PARK (22.5N 
114.3E), APPROXIMATELY 155 NM NORTH OF THE CURRENT POSITION, SHOWS 
DEEP LAYER EASTERLY FLOW, EVIDENCE OF THE STR PRESENCE IN THE 
FORECAST PATH. THE CURRENT INTENSITY IS BASED ON A BLEND OF DVORAK 
ESTIMATES RANGING FROM 45-55 KNOTS FROM PGTW/RJTD/KNES, AND THE 
222100Z OBJECTIVE SATCON ESTIMATE OF 61 KNOTS (COMPRISED 
OF CIMSS AMSU = 64 KNOTS, ADT = 55 KNOTS). ANIMATED WATER VAPOR 
IMAGERY SHOWS GOOD EQUATORWARD OUTFLOW WITH INDICATIONS OF POELWARD 
OUTFLOW FORMING. HOWEVER, DUE TO THE STRONG UPPER-LEVEL RIDGING TO 
THE NORTH, THE POLEWARD OUTFLOW IS QUICKLY DEFLECTED TO THE WEST 
AND IN ESSENCE ENHANCES THE EQUATORWARD OUTFLOW.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 09W SHOULD CONTINUE TO TRACK NORTH-NORTHWESTWARDS ALONG 
THE SOUTHWESTERN PERIPHERY OF THE STR ANCHORED TO THE NORTHEAST. 
THE SYSTEM WILL GRADUALLY INTENSIFY DUE TO FAVORABLE UPPER-LEVEL 
CONDITIONS AND WARM SEA SURFACE TEMPERATURES OF 28-30 DEGREES 
CELSIUS. TS VICENTE SHOULD MAKE LANDFALL WEST OF HONG KONG AS A 
MINIMAL STRENGTH TYPHOON OR VERY STRONG TS. THE SYSTEM WILL THEN 
GRADUALLY SPIN-DOWN DUE TO LAND INTERACTION DURING TAUS 36-48 AND 
HAVE DISSIPATED OVERLAND BY TAU 72. THE OBJECTIVE AID GUIDANCE 
CONTINUES TO UNANIMOUSLY INDICATE A NORTH-NORTHWESTWARD TRAJECTORY 
IN A TIGHT ENVELOPE. HIGH CONFIDENCE REMAINS IN THE OFFICIAL JTWC 
TRACK FORECAST DUE TO THIS TREND IN GUIDANCE DESPITE THE PAST 
RETROGRADE.//
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