WDPN31 PGTW 270300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (SON-TINH) WARNING NR 14//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 24W (SON-TINH), LOCATED APPROXIMATELY 190 NM EAST OF 
HUE, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD AT 15 KTS OVER THE PAST 
SIX HOURS. ANIMATED ENHANCED INFRARED IMAGERY DEPICTS TIGHTLY-CURVED 
CONVECTIVE BANDING WRAPPING INTO A LOW LEVEL CIRCULATION CENTER 
(LLCC). A 270027Z SSMIS 91GHZ IMAGE REVEALS GOOD BANDING, HOWEVER 
THE CONVECTION IS BEGINNING TO WEAKEN IN THE WESTERN SEMICIRCLE. THE 
INITIAL POSITION IS BASED ON THE PGTW FIX AND RECENT MICROWAVE 
IMAGERY WITH HIGH CONFIDENCE. THE INITIAL INTENSITY IS BASED ON 
DVORAK ESTIMATES OF 65 KTS FROM PGTW AND KNES. UPPER-LEVEL ANALYSIS 
CONTINUES TO DEPICT A FAVORABLE ENVIRONMENT WITH GOOD RADIAL OUTFLOW 
AND WEAK (05-10 KTS) VERTICAL WIND SHEAR (VWS). ADDITIONALLY, THE 
MOST RECENT AMSU CROSS-SECTION REVEALS A FOUR-DEGREE WARM CORE 
ANOMALY, INDICATIVE OF A STRONG SECONDARY CIRCULATION. A SEA SURFACE 
TEMPERATURE ANALYSIS INDICATES THAT TY 24W WILL MOVE OVER SLIGHTLY 
WARMER WATER AS IT ENTERS THE GULF OF TONKIN, PROVIDING SUPPORT FOR 
SLIGHT INTENSIFICATION.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING BULLETIN.
   B. TY 24W IS FORECAST TO CONTINUE TRACKING WEST-NORTHWESTWARD 
OVER THE NEXT 36 HOURS UNDER THE STEERING INFLUENCE OF THE DEEP SUB-
TROPICAL RIDGE POSITIONED TO THE NORTH. THE GOOD ENVIRONMENT NOTED 
IN THE ANALYSIS SHOULD ALLOW FOR SLIGHT INTENSIFICATION, WITH A PEAK 
FORECAST INTENSITY OF 75 KNOTS PRIOR TO LANDFALL. AFTER TAU 36, SUB-
TROPICAL WESTERLIES ARE FORECAST TO INCREASE OVER NORTHERN VIETNAM, 
RESULTING IN A TURN TO THE NORTHEAST AS THE SYSTEM RAPIDLY 
DISSIPATES DUE TO LAND INTERACTION. NUMERICAL MODEL GUIDANCE IS IN 
GOOD AGREEMENT WITH THIS GENERAL SCENARIO, ALTHOUGH THERE IS A 
GROWING SPREAD IN THE TRACK SPEEDS AFTER TAU 36 DUE TO UNCERTAINTIES 
IN THE INTERACTION WITH THE SUB-TROPICAL WESTERLIES. GFDN IS THE 
SOLE OUTLIER, WHICH TRACKS THE SYSTEM WESTWARD INTO LAOS. TY 24W IS 
FORECAST TO DISSIPATE OVER LAND BY TAU 72. BASED ON THE TIGHT 
GROUPING OF MODELS THROUGH LANDFALL, THERE IS HIGH CONFIDENCE IN THE 
JTWC FORECAST.//
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