WDPN31 PGTW 281500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (SON-TINH) WARNING NR 20//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 24W (SON-TINH), LOCATED APPROXIMATELY 70 NM SOUTHEAST
OF HANOI, VIETNAM, HAS TRACKED NORTHWARD AT 09 KNOTS OVER THE PAST
SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS THE
CONVECTIVE TOPS CONTINUED TO WARM AS THE SYSTEM VEERED ON A MORE
POLEWARD TRACK. THE INITIAL POSITION IS BASED ON THE ABOVE ANIMATION
AND EXTRAPOLATED FROM A MICROWAVE EYE FEATURE ON A 280908Z TRMM
IMAGE. THE INITIAL INTENSITY REFLECTS A WEAKENING TREND AS REPORTED
FROM DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD. UPPER LEVEL ANALYSIS
INDICATES THE SYSTEM IS CROSSING INTO THE POLEWARD SIDE OF THE RIDGE
AXIS IN AN AREA OF LIGHT TO MODERATE (10-20 KNOTS) VERTICAL WIND
SHEAR (VWS). THE CYCLONE IS ROUNDING THE WESTERN EDGE OF THE
SUBTROPICAL RIDGE (STR) TO THE EAST THAT HAS SINCE WEAKENED AND
RECEDED DUE TO THE IMPACT OF MID-LATITUDE TROUGH THAT PASSED TO
ITS NORTH.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING BULLETIN.
   B. TY SON-TINH WILL MAKE LANDFALL ALONG THE NORTHERN COAST OF
VIETNAM BY TAU 12, DRAG NORTHWARD ALONG THE COASTLINE, CROSS INTO
CHINA, THEN TURN EASTWARD INTO HAINAN. INCREASING VWS, INFLUX OF
RELATIVELY COOLER AND DRIER CONTINENTAL AIR FROM CHINA, AND LAND
INTERACTION WILL RAPIDLY WEAKEN THE CYCLONE BEFORE IT DISSIPATES BY
TAU 48. THE NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT UP TO TAU
36, AFTER WHICH THE MODELS SPREAD DUE TO UNCERTAINTIES IN THE
INTERACTION OF THE SYSTEM WITH THE MID-LATITUDE WESTERLIES AND
TERRAIN EFFECTS. THIS FORECAST IS CLOSE TO CONSENSUS, ECMWF, AND GFS.
THERE IS HIGH CONFIDENCE IN THE TRACK FORECAST UP TO TAU 36.    //
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