WDPN31 PGTW 151500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (TALIM)         
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.4N 117.5E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 299 NM SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 04W HAS TRACKED SLOWLY NORTHWESTWARD TOWARD A 
BREAK IN THE LOW- TO MID-LEVEL SUBTROPICAL RIDGE ASSOCIATED WITH THE 
PASSAGE OF AN UPPER-LEVEL SHORTWAVE TROUGH TO THE NORTH. ANIMATED 
PROXYVIS SATELLITE IMAGERY REVEALS IMPROVED CONVECTIVE BANDING 
WRAPPING INTO A DEFINED, PARTIALLY EXPOSED LOW-LEVEL CIRCULATION 
CENTER (LLCC). A 150908Z SSMIS 91GHZ COLOR COMPOSITE MICROWAVE IMAGE 
SHOWS SLIGHTLY IMPROVED CORE STRUCTURE WITH CONVECTIVE BANDING 
WRAPPING INTO A BROAD LLCC. ALTHOUGH VERTICAL WIND SHEAR (VWS) 
REMAINS AT LOW TO MODERATE LEVELS, ANIMATED WATER VAPOR IMAGERY SHOWS 
A MODEST IMPROVEMENT IN EASTWARD OUTFLOW, WHICH APPEARS TO BE KEY TO 
THE RECENT IMPROVEMENT IN CORE STRUCTURE, AND VIGOROUS EQUATORWARD 
OUTFLOW. POLEWARD OUTFLOW IS LIMITED DUE TO CONVERGENT FLOW ALONG THE 
NORTHWESTERN PERIPHERY OF THE SYSTEM. THE INITIAL POSITION IS PLACED 
WITH MEDIUM CONFIDENCE BASED ON THE PROXYVIS IMAGERY AND THE RECENT 
SSMIS IMAGE. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM 
CONFIDENCE AND IS HEDGED ABOVE THE PGTW, KNES, RJTD DVORAK ESTIMATES 
BASED ON THE CIMSS ADT ESTIMATE AND A 151200Z D-PRINT ESTIMATE OF 41 
KNOTS.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: WEAK EXTENSION OF THE LOW- TO MID-LEVEL
SUBTROPICAL RIDGE POSITIONED TO THE NORTH AND NORTHEAST WITH AN
UPPER-LEVEL SHORTWAVE TROUGH OVER EAST CENTRAL CHINA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 39 KTS AT 151140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TS 04W IS EXPECTED TO TRACK STEADILY WEST-
NORTHWESTWARD ALONG THE SOUTHWESTERN FLANK OF THE SUBTROPICAL
RIDGE, WHICH IS FORECAST TO REBUILD AS THE SHORTWAVE TROUGH FILLS 
AND PROPAGATES NORTHEASTWARD OVER THE NEXT 12 HOURS. ENVIRONMENTAL 
CONDITIONS ARE EXPECTED TO GRADUALLY IMPROVE WITH DECREASING 
NORTHEASTERLY VWS AND IMPROVED POLEWARD OUTFLOW INTO THE SUBTROPICAL 
WESTERLIES OVER CENTRAL CHINA. THIS SHOULD ALLOW THE SYSTEM TIME TO 
RAPIDLY CONSOLIDATE AFTER TAU 12 WITH A HIGH PROBABILITY OF RAPID 
INTENSIFICATION PRIOR TO LANDFALL NEAR TAU 60. THUS THE PEAK OF 85 
KNOTS IS EXPECTED IN THE TAU 48 TO TAU 60 WINDOW. AFTER TAU 60, TS 
04W WILL WEAKEN SIGNIFICANTLY AS IT INTERACTS WITH HAINAN ISLAND AND 
SOUTHERN CHINA THEN QUICKLY CROSSES THE GULF OF TONKIN MAKING 
LANDFALL OVER VIETNAM NEAR TAU 72. THE SYSTEM WILL RAPIDLY DISSIPATE 
OVER NORTHERN VIETNAM THROUGH THE EXTENDED FORECAST PERIOD.       

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
THROUGH TAU 72 WITH A 165NM CROSS-TRACK SPREAD AT TAU 72. NAVGEM
AND ECMWF REMAIN ON THE SOUTHERN EDGE OF THE AIDS ENVELOPE WITH A
TRACK OVER THE SOUTHERN LEIZHOU PENINSULA WHILE THE BULK OF THE 
MODELS INDICATE A MORE WEST-NORTHWESTWARD TRACK OVER OR TO THE NORTH 
OF THE LEIZHOU PENINSULA. AFTER TAU 72, NUMERICAL MODEL GUIDANCE 
DIVERGES DUE TO THE WEAKENING LOW-LEVEL VORTEX. THE 150000Z COAMPS-TC 
ENSEMBLE CONTINUES TO INDICATE A PEAK RAPID INTENSIFICATION 
PROBABILITY OF 80 PERCENT IN THE TAU 18 TO TAU 48 PERIOD.    

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: HIGH//
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