WDPN31 PGTW 231500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (TEMBIN) WARNING NR 19//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 15W (TEMBIN), LOCATED APPROXIMATELY 150 NM SOUTH-
SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED WESTWARD AT 06 KNOTS OVER 
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY 
SHOWS THE EYE HAS BECOME MORE SYMMETRIC WITH THE OVERALL STRUCTURE 
OF THE SYSTEM REMAINING WELL ORGANIZED AND COMPACT. THE DUAL BANDING 
FEATURES ALONG THE NORTHERN AND SOUTHERN HALVES CONTINUE TO FEED THE 
LOW LEVEL CIRCULATION CENTER (LLCC). UPPER LEVEL ANALYSIS INDICATES 
THE DUAL CHANNEL OUTFLOW TO THE POLEWARD AND EQUATORWARD DIRECTIONS 
HAS BEEN INSTRUMENTAL IN THE SYSTEM MAINTAINING THE CURRENT 
INTENSITY OF 105 KNOTS. THE TRACK SPEED HAS INCREASED SLIGHTLY OVER 
THE PAST SIX HOURS AS TY 15W TRACKS ALONG THE SOUTHERN PERIPHERY OF 
A DEEP-LAYERED SUBTROPICAL RIDGE ANCHORED JUST EAST OF HONSHU, 
JAPAN.  
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TY 15W WILL CONTINUE TO STEER WESTWARD INTO TAIWAN WITHIN THE 
NEXT 12 HOURS. INTENSITY IS EXPECTED TO REMAIN STEADY UNTIL MAKING 
LANDFALL, WITH A MINOR WEAKENING TREND OBSERVED DUE TO THE PASSAGE 
OF THE SYSTEM OVER TAIWAN. TY 15W WILL BEGIN TO SLOW AS THE STR 
WEAKENS UNDER THE INFLUENCE OF A DIGGING MID-LATITUDE TROUGH TO THE 
NORTH AND A BUILDING NEAR EQUATORIAL RIDGE (NER) TO THE SOUTHEAST. 
INCREASING VERTICAL WIND SHEAR AND DIMINISHED UPPER LEVEL OUTFLOW 
WILL LEAD TO A SLIGHT WEAKENING THROUGH TAU 72.
   C. AFTER TAU 72, TYPHOON TEMBIN IS EXPECTED TO SLOWLY TRACK EAST-
NORTHEASTWARD IN A TIGHT COUNTER-CLOCKWISE LOOPING MOTION AS THE NER 
BUILDS AND THE APPROACHING TY 16W (BOLAVEN) WILL BE AT ITS CLOSEST 
POINT OF APPROACH TO TY 15W CAUSING POSSIBLE INCREASED BINARY 
INTERACTION. FURTHER HINDRANCE OF THE UPPER LEVEL OUTFLOW WILL 
PERSIST IN WEAKENING TY 15W THROUGH THE REMAINDER OF THE FORECAST 
PERIOD. DYNAMIC MODEL GUIDANCE REMAINS IN FAIR AGREEMENT WITH THE 
LOOP IN THE NEXT 48 TO 72 HOURS HOWEVER THERE IS A LARGE DISPARITY 
WITH THE EXTENDED FORECAST TRACK DEPICTIONS. BASED ON THIS LARGE 
VARIATION IN FORECAST GUIDANCE AND THE TIMING OF THE LOOPING MOTION, 
THERE REMAINS LOW CONFIDENCE IN THE EXTENDED FORECAST TRACK.//
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