WDPN31 PGTW 091500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W WARNING NR 07//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TYPHOON (TY) 11W (MERANTI), LOCATED APPROXIMATELY 180 NM 
SOUTHWEST OF TAIPEI, TAIWAN, HAS TRACKED NORTH-NORTHWESTWARD AT 10 
KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED (IR) SATELLITE 
IMAGERY SHOWS A MIDGET SYSTEM WITH A WELL-DEFINED LOW LEVEL 
CIRCULATION CENTER (LLCC) AND A 091128Z SSMIS DEPICTS A DEEP 
CONVECTIVE MICROWAVE EYE. THE INITIAL POSITION IS BASED ON A RADAR 
FIX FROM TAIWAN AND THE AFOREMENTIONED SSMIS IMAGE WITH HIGH 
CONFIDENCE. THE INITIAL INTENSITY IS BASED ON THE CONVECTIVE 
SIGNATURE AND NOT ON DVORAK ESTIMATES BECAUSE THEY ARE 
UNDERESTIMATING THIS MIDGET SYSTEM. UPPER LEVEL ANALYSIS INDICATES 
A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL HAS CONTINUED TO 
MOVE FARTHER NORTHWESTWARD, WHICH HAS ALLOWED IMPROVED POLEWARD 
OUTFLOW AND DECREASED VERTICAL WIND SHEAR (VWS). ADDITIONALLY, TY 
11W CONTINUES TO MAINTAIN A GOOD EQUATORWARD OUTFLOW CHANNEL, 
ALLOWING IT TO RAPIDLY INTENSIFY.
3. FORECAST REASONING.
   A. THE CURRENT INTENSITY HAS INCREASED SIGNIFICANTLY SINCE THE 
PREVIOUS FORECAST BECAUSE OF THE DECREASED VWS AND DUAL OUTFLOW 
CHANNELS. THE FORECAST TRACK PHILOSOPHY HAS GENERALLY REMAINED THE 
SAME EXCEPT FOR AN INCREASE IN TRACK SPEED DUE TO A STRAIGHTER TRACK.
   B. TY 11W IS CURRENTLY TRACKING ALONG THE WESTERN PERIPHERY OF A 
SUBTROPICAL STEERING RIDGE AND IS EXPECTED TO MAKE LANDFALL IN 
APPROXIMATELY 12 HOURS OVER SOUTHEASTERN CHINA. TY 11W SHOULD BEGIN 
TO FEEL THE AFFECTS OF LAND AND BEGIN TO WEAKEN BY TAU 12. BY TAU 
36, TY MERANTI IS EXPECTED TO DISSIPATE AS A SIGNIFICANT TROPICAL 
CYCLONE OVER THE MOUNTAINOUS TERRAIN OF CHINA. NUMERICAL MODEL 
GUIDANCE IS IN GOOD AGREEMENT WITH THE EXCEPTION OF THE UKMO MODEL 
WHICH ERRONEOUSLY TRACKS THE SYSTEM NORTHEASTWARD TOWARDS TAIWAN 
BEFORE TURNING IT NORTHWARD. THIS FORECAST IS SLIGHTLY WEST OF 
CONSENSUS TO ACCOUNT FOR THE UKMO MODEL AND IS WITHIN THE TIGHT 
MODEL PACKING OF WBAR, ECMWF, NOGAPS, JGSM, AND GFS.//
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