WDPN31 PGTW 180300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W WARNING NR 14//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TYPHOON (TY) 12W (FANAPI), LOCATED APPROXIMATELY 270 NM EAST-
SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED WESTWARD AT 07 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL IMAGERY SHOWS A 20 
NM EYE AND A 172216Z SSMIS MICROWAVE IMAGE DEPICTS MULTIPLE 
CONVECTIVE BANDS ALONG THE EASTERN PERIPHERY. THERE IS HIGH 
CONFIDENCE IN THE INITIAL POSITION BASED ON AN EYE FIX. THE INITIAL 
INTENSITY IS BASED ON THE 172301Z AND 180006Z VORTEX DATA MESSAGES 
INDICATING SURFACE WIND SPEED ESTIMATES OF 93 AND 95 KNOTS. THERE IS 
ALSO HIGH CONFIDENCE IN THE WIND RADII STRUCTURE, WHICH WAS BASED ON 
DOTSTAR DROPSONDE OBSERVATIONS. UPPER LEVEL ANALYSIS INDICATES 
INCREASED NORTHEASTERLY VERTICAL WIND SHEAR ALONG THE NORTHERN 
PERIPHERY OF THE SYSTEM. ADDITIONALLY, WATER VAPOR SATELLITE IMAGERY 
SHOWS EXCELLENT UPPER LEVEL EQUATORWARD OUTFLOW AND DECREASING 
POLEWARD OUTFLOW AS A MID-LATITUDE TROUGH MOVES FARTHER 
NORTHEASTWARD. TY 12W IS CURRENTLY TRACKING ALONG THE SOUTHERN 
PERIPHERY OF A SUBTROPICAL STEERING RIDGE LOCATED TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE IN FORECAST PHILOSOPHY AND TRACK SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 12W IS FORECAST TO CONTINUE TRACKING WESTWARD ALONG THE 
SOUTHERN PERIPHERY OF THE SUBTROPICAL STEERING RIDGE THROUGHOUT THE 
FORECAST PERIOD. ALTHOUGH POLEWARD OUTFLOW IS DECREASING, FAVORABLE 
EQUATORWARD OUTFLOW WILL ALLOW TY FANAPI TO SLIGHTLY INCREASE IN 
INTENSITY WITHIN THE NEXT 12 HOURS. AFTER TAU 24, TY FANAPI IS 
EXPECTED TO MAKE LANDFALL OVER TAIWAN, WHERE IT WILL WEAKEN 
SIGNIFICANTLY. THE SYSTEM SHOULD CONTINUE WESTWARD MAKING LANDFALL 
OVER CHINA BY TAU 48. NUMERICAL MODEL GUIDANCE IS IN TIGHT 
AGREEMENT, THEREFORE THERE IS HIGH CONFIDENCE IN THE TRACK FORECAST.
   C. IN THE EXTENDED PERIOD, TY 12W IS EXPECTED TO DISSIPATE BY
TAU 96.//
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