WDPN31 PGTW 300300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (RUMBIA) WARNING 
NR 09//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 06W (RUMBIA), LOCATED APPROXIMATELY 64 NM 
WESTWARD OF MANILA, PHILIPPINES, HAS TRACKED WEST-
NORTHWESTWARD AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED 
MULTI-SPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A CONSOLIDATION 
OF DEEP CONVECTION INTO A CENTRAL DENSE OVERCAST, WITH TIGHTLY 
CURVED BANDING (TCB) WRAPPING INTO THE LOW LEVEL CIRCULATION CENTER. 
THE TCB IS APPARENT IN A 292147Z SSMIS 91 GHZ IMAGE AS WELL AS 
ANIMATED RADAR IMAGERY FROM SUBIC STATION, WHICH CLEARLY SHOWS THE 
LLCC HAS NOW TRACKED INTO THE SOUTH CHINA SEA. THERE IS GOOD 
CONFIDENCE IN THE INITIAL POSITION BASED ON ALL THE AFOREMENTIONED 
DATA. ALTHOUGH DVORAK INTENSITY ESTIMATES ARE BETWEEN 30-35 KNOTS, 
THE INITIAL INTENSITY IS ASSESSED AT 40 KNOTS, TAKING INTO ACCOUNT 
HIGHER ESTIMATES FROM AUTOMATED TECHNIQUES AS WELL AS THE STRUCTURE 
NOTED IN MICROWAVE IMAGERY. THE 300000Z SURFACE WIND OBSERVATION 
FROM OLONGAPO, PHILIPPINES IS 18 KNOTS FROM THE EAST. TS 06W IS 
TRACKING QUICKLY ALONG THE SOUTHERN PERIPHERY OF A DEEP SUBTROPICAL 
RIDGE (STR). UPPER-LEVEL ANALYSIS INDICATES A GENERALLY FAVORABLE 
ENVIRONMENT WITH GOOD OUTFLOW, PARTICULARLY IN THE EQUATORWARD 
DIRECTION. ANIMATED WATER VAPOR IMAGERY SUGGESTS THE WEAK POLEWARD 
OUTFLOW IS TRYING TO LINK UP WITH A MID-LATITUDE JET EAST OF TAIWAN, 
WHICH COULD FURTHER IMPROVE THE ENVIRONMENT FOR INTENSIFICATION IN 
THE SHORT TERM. THERE IS MODERATE (10-15 KNOTS) VERTICAL WIND SHEAR 
(VWS) FROM THE NORTHEAST. SEA SURFACE TEMPERATURES ARE VERY 
FAVORABLE ALONG THE FORECAST TRACK.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY 
FROM THE PREVIOUS PROGNOSTIC REASONING BULLETIN.
   B. TS 06W IS FORECAST TO TRACK GENERALLY NORTHWESTWARD ALONG THE 
SOUTHERN AND SOUTHWESTERN PERIPHERY OF THE STR THROUGH TAU 72. OVER 
THE PAST 12 HOURS, THE STRENGTH OF THE STR HAS KEPT 06W TRACKING IN 
A MORE WEST-NORTHWESTERLY DIRECTION THAN PREVIOUSLY FORECAST. THIS 
HAS RESULTED IN A WESTWARD SHIFT OF THE EVENTUAL LANDFALL POSITION 
BY APPROXIMATELY 55 NM. THE MAJORITY OF THE DYNAMIC MODEL GUIDANCE 
IS IN SOLID AGREEMENT THROUGH LANDFALL (SHORTLY BEFORE 
TAU 48). GFDN AND THE JGSM ENSEMBLE AVERAGE ARE NOW THE OUTLIERS, 
TAKING A MORE WESTERLY TRACK TOWARDS VIETNAM. AFTER TAU 48, THE 
MODELS DIVERGE WITH SIGNIFICANT DIFFERENCES IN THE TIMING AND DEGREE 
OF THE TURN NORTHWARD, WITH NAVGEM AND GFDN TAKING A MORE WEST-
NORTHWESTWARD TRACK VICE CONTINUING TO TRACK NORTHWARD ALONG THE 
STR. TS 06W IS FORECAST TO INTENSIFY TO A PEAK OF 55 KNOTS OVER THE 
NEXT 24 HOURS. AFTER TAU 36, A SIGNIFICANT INCREASE OF NORTHERLY VWS 
ASSOCIATED WITH THE UPPER-LEVEL STR OVER EASTERN CHINA WILL BEGIN TO 
WEAKEN THE SYSTEM. THE SYSTEM IS FORECAST TO MAKE LANDFALL BEFORE 
TAU 48 APPROXIMATELY 155 NM SOUTHWEST OF HONG KONG, AND IS EXPECTED 
TO RAPIDLY WEAKEN DUE TO LAND INTERACTION AND VWS. THERE IS SOME 
UNCERTAINTY IN THE EXACT TRACK AFTER TAU 48 BUT GOOD CONFIDENCE IN 
THE LANDFALL POSITION. THE SYSTEM WILL DISSIPATE BY TAU 72. 
OVERALL, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
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