WDPN32 PGTW 140300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (VAMCO) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 25W (VAMCO), LOCATED APPROXIMATELY 174 NM EAST OF DA 
NANG, VIETNAM, HAS TRACKED WESTWARD AT 11 KNOTS OVER THE PAST SIX 
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SPIRAL 
BANDS OF DEEP CONVECTION WRAPPING INTO A 15NM ELONGATED EYE. THE 
INITIAL POSITION IS SET WITH HIGH CONFIDENCE BASED ON THE WELL DEFINED 
EYE IN THE MSI LOOP. THE INITIAL INTENSITY IS PLACED WITH HIGH 
CONFIDENCE 
BASED ON MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF 
T5.5 (102 KTS, PGTW AND RJTD), AN ADVANCED DVORAK TECHNIQUE CURRENT 
INTENSITY ESTIMATE OF T6.3 (122 KNOTS) AND A 132251Z CIMSS SATELLITE 
CONSENSUS INTENSITY ESTIMATE OF 108 KTS. TY VAMCO RESIDES IN 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 IS 
TRACKING SLIGHTLY WEST OF THE POINT SOURCE ALOFT AND HAS MAINTAINED 
NEAR RADIAL OUTFLOW IN A LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS) 
WEST OF THE SUBTROPICAL RIDGE (STR). 
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. THE 
SYSTEM WILL WEAKEN AS IT MOVES OVER DECREASING OHC AND SST NEAR 
COASTAL VIETNAM BY TAU 12. THEREAFTER, THE SYSTEM WILL 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, AND WEAKEN EVEN MORE DUE TO 
UNFAVORABLE VWS AND SSTS. TY VAMCO WILL MAKE LANDFALL NORTH OF HUE, 
VIETNAM IN BETWEEN TAU 24 AND 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 48 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 194 NM SPREAD AT 
LANDFALL. 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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