WDPN32 PGTW 101500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (VAMCO) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 25W (VAMCO), LOCATED APPROXIMATELY 333 NM
EAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT 13 
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE 
SHOWS A CONSOLIDATING SYSTEM WITH CURVED RAIN BANDS THAT HAVE 
WRAPPED TIGHTER INTO AN OBSCURED LOW LEVEL CIRCULATION. THE INITIAL 
POSITION AND INTENSITY ARE PLACED WITH HIGH CONFIDENCE BASED ON A 
101137Z ASCAT BULLSEYE PASS WITH 45KT WIND BARBS ALONG THE NORTHEAST 
QUADRANT, AND CONSISTENT WITH CONGRUENT DVORAK ESTIMATES OF 
T3.0/45KTS FROM PGTW, KNES, AND RJTD. UPPER LEVEL ANALYSIS INDICATES 
THE SYSTEM REMAINS IN A FAVORABLE AREA WITH LOW (05-10KT) VERTICAL 
WIND SHEAR (VWS) AND STRONG RADIAL OUTFLOW ASSOCIATED WITH A POINT 
SOURCE DIRECTLY OVERHEAD. ADDITIONALLY, SEA SURFACE TEMPERATURES 
(SST) IN THE PHILIPPINE SEA REMAIN WARM AT 29-30C. THE CYCLONE IS 
TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE 
(STR) TO THE NORTHEAST.  
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. AS THE STR BUILDS, TS 25W WILL TRACK ON A MORE WESTWARD 
TRAJECTORY TOWARD THE PHILIPPINES, PASSING JUST TO THE NORTH OF 
CAMARINES NORTE BEFORE MAKING LANDFALL OVER THE PROVINCE OF BULACAN 
AROUND TAU 30. AFTERWARD, IT WILL DRAG ACROSS THE NATIONAL CAPITAL 
REGION JUST NORTH OF MANILA BEFORE EXITING INTO THE SOUTH CHINA SEA 
(SCS) SHORTLY BEFORE TAU 36. THE FAVORABLE ENVIRONMENT WILL FUEL A 
RAPID INTENSIFICATION TO 80KTS BY TAU 24 JUST BEFORE LANDFALL. 
AFTERWARD, LAND INTERACTION WILL ERODE THE SYSTEM DOWN TO 70KTS AS 
IT EXITS INTO THE WARM SCS WHERE IT WILL RE-CONSOLIDATE AND 
STRENGTHEN SLIGHTLY TO 75KTS BY TAU 72. NUMERICAL MODELS ARE IN 
TIGHT AGREEMENT, LENDING HIGH CONFIDENCE TO THIS PORTION OF THE JTWC 
TRACK FORECAST.
   C. AFTER TAU 72, TS VAMCO WILL TRACK WEST-NORTHWESTWARD AS THE 
STR IS WEAKENED BY AN APPOACHING MIDLATITUDE TROUGH AND WILL MAKE 
LANDFALL OVER CENTRAL VIETNAM SOUTH OF DANANG JUST AFTER TAU 96. AS 
THE SYSTEM TRACKS FURTHER WEST IN THE SCS, DECREASING SST (24C) AND 
SIGNIFICANTLY LOWER OCEAN HEAT CONTENT (<25KJ/CM^2) WILL WEAKEN THE 
SYSTEM DOWN TO 50KTS BY TAU 96 BEFORE LANDFALL. AFTERWARD, THE 
RUGGED TERRAIN WILL RAPIDLY ERODE THE SYSTEM DOWN TO 30KTS BY TAU 
120 AFTER IT CROSSES INTO LAOS. NUMERICAL MODELS GRADUALLY AND 
EVENLY SPREAD TO OVER 280NM BY TAU 12O. THE EXTENDED PORTION OF THE 
JTWC TRACK FORECAST IS LAID WITH FAIR CONFIDENCE NEAR THE MODEL 
CONSENSUS.//
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