WDPN32 PGTW 132100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (VAMCO) WARNING NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 25W (VAMCO), LOCATED APPROXIMATELY 296 NM EAST OF DA 
NANG, VIETNAM, HAS TRACKED WESTWARD AT 10 KNOTS OVER THE PAST SIX 
HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS 
SPIRAL BANDS OF DEEP CONVECTION RAPPING INTO A 20NM ELONGATED EYE. 
THE INITIAL POSITION IS SET WITH HIGH CONFIDENCE BASED ON THE WELL 
DEFINED EYE IN THE EIR LOOP. THE INITIAL INTENSITY IS PLACED WITH 
HIGH CONFIDENCE BASED ON MULTI-AGENCY DVORAK CURRENT INTENSITY 
ESTIMATES OF T6.0 (115 KTS, PGTW) T5.5 (102 KTS, RJTD), AN ADVANCED 
DVORAK TECHNIQUE CURRENT INTENSITY ESTIMATE OF T6.6 (130 KNOTS) 
AND A 131117Z SATELLITE CONSENSUS ESTIMATE OF 103 KNOTS. TY VAMCO 
IS CURRENTLY APPROACHING A COL REGION WITHIN THE SUBTROPICAL RIDGE 
(STR) POSITIONED TO THE NORTHEAST. AND THROUGH A MARGINAL ENVIRONMENT 
WITH WARM (27 CELSIUS) SEA SURFACE TEMPERATURES (SST) OFFSET BY VERY 
LOW OCEAN HEAT CONTENT (OHC) (< 10 KILOJOULES PER SQUARE CENTIMETER). 
UPPER-LEVEL ANALYSIS FURTHER INDICATES THAT TY 25W HAS BEGUN TO TRACK 
SLIGHTLY WEST OF THE POINT SOURCE ALOFT AND HAS MAINTAINED NEAR RADIAL 
OUTFLOW IN A LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS) ENVIRONMENT. 
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC 
REASONING MESSAGE. 
   B. TY VAMCO WILL CONTINUE TO TRACK WEST TO WEST-NORTHWESTWARD THROUGH 
THE REMAINDER OF THE FORECAST PERIOD UNDER THE STEERING INFLUENCE OF 
THE AFOREMENTIONED STR CENTERED TO THE NORTHEAST. AFTER A BRIEF PERIOD 
OF RAPID INTENSIFICATION, THE SYSTEM IS NOW FORECAST TO WEAKEN STEADILY 
TO 100 KTS BY TAU 12 DUE TO DECREASING OHC AND SST. THEREAFTER, THE SYSTEM 
WILL BEGIN TO RAPIDLY WEAKEN TO 80 KTS BY TAU 24 DUE TO MODERATE (15-20 KTS) 
VWS AND UNFAVORABLE, COOL (< 26 CELSIUS) SST. THE SYSTEM WILL CONTINUE TO 
TRACK NORTHWESTWARD AFTER TAU 24, CONTINUE TO WEAKEN DUE TO THE UNFAVORABLE 
VWS AND SST, AND MAKE LANDFALL NORTH OF HUE, VIETNAM BY TAU 36 AS A TYPHOON. 
THEREAFTER, THE SYSTEM WILL RAPIDLY DECAY AND BEGIN DISSIPATION OVER LAND 
DUE TO INTERACTION WITH THE UNDERLYING TERRAIN AS WELL AS THE CONTINUED, 
UNFAVORABLE VWS. BY TAU 72 THE SYSTEM IS FORECAST TO FULLY DISSIPATE OVER 
LAND AS IT TRACKS OVER LAOS. NUMERICAL MODEL TRACK GUIDANCE CONTINUES TO 
PROVIDE A HIGH DEGREE OF SPREAD IN MODEL SOLUTIONS WITH A 270NM SPREAD AT 
LANDFALL THAT DECREASES TO 120NM WHEN THE UKMET AND AFUM MODEL TRACKS, 
WHICH BRING THE VORTEX FARTHER NORTH THAN THE OTHER MEMBERS OF THE MULTI-MODEL 
CONSENSUS, ARE REMOVED. THIS SPREAD IN MODEL SOLUTIONS LENDS OVERALL FAIR 
CONFIDENCE IN THE JTWC FORECAST TRACK WHICH IS PLACED ALONG THE MULTI-MODEL 
CONSENSUS.//
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