WDPN31 PGTW 081500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (FENGSHEN) WARNING 
NR 07//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 13W (FENGSHEN), LOCATED APPROXIMATELY 264 NM 
SOUTH OF YOKOSUKA, JAPAN, HAS TRACKED EAST-NORTHEASTWARD AT 23 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE 
IMAGERY (MSI) DEPICTS TIGHTLY-CURVED BANDING OVER THE NORTHERN 
PERIPHERY WRAPPING INTO A WELL-DEFINED LOW LEVEL CIRCULATION CENTER 
(LLCC). A 081210Z METOP-B MICROWAVE IMAGE ALSO REVEALS A ROUND 
MICROWAVE EYE WITH THE BULK OF THE DEEP CONVECTIVE BANDING OVER THE 
NORTHERN SEMI-CIRCLE WRAPPING INTO THE LLCC. THE CURRENT POSITION IS 
BASED ON THE EIR ANIMATION AND AFOREMENTIONED MICROWAVE IMAGE WITH 
HIGH CONFIDENCE. THE INITIAL INTENSITY OF 55 KNOTS IS BASED ON 
MATCHING DVORAK INTENSITY ESTIMATES FROM ALL REPORTING AGENCIES. 
UPPER-LEVEL ANALYSIS INDICATES TS FENGSHEN CONTINUES TO HAVE 
EXCELLENT POLEWARD OUTFLOW OFFSETTING THE MODERATE TO HIGH LEVELS 
(20 TO 30 KNOTS) OF VERTICAL WIND SHEAR (VWS). TS 13W CONTINUES TO 
TRACK ALONG THE NORTHWESTERN PERIPHERY OF A DEEP LAYERED SUBTROPICAL 
RIDGE (STR) TO THE SOUTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 13W IS EXPECTED TO TRACK NORTHEASTWARD ALONG THE STR 
THROUGHOUT THE FORECAST PERIOD. DESPITE THE SUBSIDENCE ALONG THE 
WESTERN PERIPHERY AND INCREASING VWS, FAVORABLE SEA SURFACE 
TEMPERATURES AND STRONG POLEWARD OUTFLOW WILL ALLOW TS 13W TO 
INTENSIFY OVER THE NEXT 24 HOURS, LEADING TO A PEAK INTENSITY OF 60 
KNOTS. INTERACTION WITH THE BAROCLINIC ZONE AROUND TAU 24 WILL BEGIN 
THE EXTRA-TROPICAL TRANSITION PROCESS AND COMPLETE ITS 
TRANSFORMATION INTO A STORM-FORCE COLD-CORE LOW BY THE END OF THE 
FORECAST. ADDITIONALLY, THE INCREASING INTERACTION WITH THE MID-
LATITUDE WESTERLIES, AS THE SYSTEM BECOMES EMBEDDED, WILL LEAD TO 
FASTER TRACK SPEEDS IN THE LATER TAUS. DYNAMIC MODEL GUIDANCE 
REMAINS IN GOOD AGREEMENT, LENDING HIGH CONFIDENCE IN THE JTWC 
FORECAST.//
NNNN