WDPN32 PGTW 112100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (VAMCO) WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 25W (VAMCO), LOCATED APPROXIMATELY 30 NM NORTHEAST 
OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 15 KNOTS OVER THE 
PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY 
INDICATES THE SYSTEM INTENSIFIED SLIGHTLY JUST PRIOR TO LANDFALL, 
WHICH OCCURRED AT ABOUT 11/1630Z TO 11/17Z. BASED ON A 15-20NM 
RAGGED EYE, ADT ESTIMATES AT THAT TIME RANGED FROM 5.7-5.9 (105-115 
KNOTS); UNOFFICIAL PGTW SUBJECTIVE DVORAK ESTIMATES RANGED FROM T5.0 
(90 KNOTS) TO A WEAK T5.5 (102 KNOTS); A PARTIAL 111716Z ASMR2 
WINDSPEED PRODUCT INDICATED MAXIMUM WINDS OF 88 KNOTS OVER THE 
NORTHEAST QUADRANT; AND AN EARLIER 110935Z SMAP ESTIMATE INDICATED 
MAXIMUM WINDS OF 99 KNOTS (10-MINUTE AVERAGE). OVERALL, THIS 
SUPPORTS THE 11/18Z INTENSITY ESTIMATE OF 95 KNOTS. AFTER LANDFALL, 
EIR AND A 111716Z AMSR2 89GHZ IMAGE REVEAL AN ABRUPT WEAKENING TREND 
WITH THE LOSS OF THE EYE FEATURE AND TIGHTLY-CURVED BANDING WRAPPING 
INTO A DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC), WHICH SUPPORTS 
THE INITIAL POSITION WITH GOOD CONFIDENCE. UPPER-LEVEL ANALYSIS 
DEPICTS A FAVORABLE ENVIRONMENT WITH RADIAL OUTFLOW AND ENHANCED 
POLEWARD OUTFLOW ASSOCIATED WITH THE WESTERLIES TO THE NORTH, AND 
LOW VERTICAL WIND SHEAR (VWS). HOWEVER, INTERACTION WITH THE 
MOUNTAIN RANGES OVER SOUTHERN LUZON IS CONTRIBUTING TO THE CURRENT 
WEAKENING TREND. TY 25W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY 
OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE 
NORTHEAST.  
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TY 25W IS FORECAST TO TRACK WESTWARD THROUGH TAU 48 UNDER THE 
STEERING INFLUENCE OF THE STR POSITIONED TO THE NORTH. TRACK SPEEDS 
ARE EXPECTED TO DECREASE AS THE SYSTEM TRANSITS SOUTH OF A BREAK IN 
THE STR. AFTER TAU 48, TY 25W SHOULD TURN WEST-NORTHWESTWARD AS IT 
TRACKS ALONG THE SOUTHWEST PERIPHERY OF THE STR. AFTER TRACKING OVER 
WARM WATER (28-29C), TY 25W SHOULD RE-INTENSIFY TO A PEAK OF 80 
KNOTS BY TAU 36. HOWEVER, SST VALUES ARE EXPECTED TO COOL TO 26-27C, 
WITH VERY LOW OCEAN HEAT CONTENT VALUES, WHICH SUPPORTS THE GRADUAL 
WEAKENING TREND THROUGH TAU 72. NUMERICAL MODEL GUIDANCE DIVERGES 
THROUGH THE FORECAST PERIOD WITH A 175NM SPREAD IN SOLUTIONS AT TAU 
72.       
   C. AFTER TAU 72, TY 25W WILL WEAKEN AS IT APPROACHES THE COAST OF 
VIETNAM AND SHOULD MAKE LANDFALL NEAR TAU 84. AFTER TAU 84, THE 
SYSTEM WILL RAPIDLY DISSIPATE AS IT TRACKS WEST-NORTHWESTWARD OVER 
THE MOUNTAINOUS TERRAIN OF VIETNAM AND CAMBODIA. NUMERICAL MODEL 
GUIDANCE IS IN FAIR AGREEMENT LENDING MODERATE CONFIDENCE IN THE 
JTWC FORECAST TRACK.//
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