WDPN31 PGTW 071500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (FENGSHEN) WARNING 
NR 03//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 13W (FENGSHEN), LOCATED APPROXIMATELY 341 NM
SOUTH-SOUTHEAST OF SASEBO, JAPAN, HAS TRACKED EAST-NORTHEASTWARD
AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED 
(EIR) SATELLITE IMAGERY SHOWS IMPROVEMENT IN THE ORGANIZATION OF THE 
CONVECTIVE BANDING AROUND THE LOW-LEVEL CIRCULATION CENTER, AS 
EVIDENT IN A 070917Z SSMIS MICROWAVE IMAGE. THE CURRENT POSITION IS 
BASED ON THE EIR ANIMATION AND AFOREMENTIONED MICROWAVE IMAGE WITH 
GOOD CONFIDENCE. THE INITIAL INTENSITY HAS INCREASED TO 45 KNOTS 
BASED ON MATCHING DVORAK INTENSITY ESTIMATES FROM ALL REPORTING 
AGENCIES. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM IS LOCATED IN AN 
AREA OF MODERATE (10 TO 20 KNOT) VERTICAL WIND SHEAR (VWS) OFFSET BY 
EXCELLENT EQUATORWARD AND POLEWARD OUTFLOW, AS EVIDENT IN THE WATER 
VAPOR IMAGERY. TS 13W CONTINUES TO ACCELERATE ALONG THE NORTHWESTERN 
PERIPHERY OF A DEEP LAYERED SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST.
3. FORECAST REASONING.
   A. THE INITIAL INTENSITY HAS BEEN INCREASED DUE TO INCREASED 
CONSOLIDATION OVER THE PAST SIX HOURS. THEREFORE, THE INTENSITY 
FORECAST HAS INCREASED THROUGHOUT THE FORECAST PERIOD.
   B. TS 13W IS FORECAST TO CONTINUE TRACKING NORTHEASTWARD ALONG 
THE STR THROUGH TAU 72. 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 
48 HOURS, LEADING TO A PEAK INTENSITY OF 60 KNOTS. INTERACTION WITH 
THE BAROCLINIC ZONE AROUND TAU 36 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.//
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