WDPN31 PGTW 181500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (LEEPI) WARNING 
NR 04//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 04W (LEEPI), LOCATED APPROXIMATELY 428 NM SOUTHWARD
OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTHWARD AT 11 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
SHOWS FORMATIVE BANDS HAVE MAINTAINED A TIGHT WRAP AROUND THE
LOW-LEVEL CIRCULATION CENTER EVEN AS CONVECTION REMAINED SHALLOW AND
FRAGMENTED. THE INITIAL POSITION IS BASED ON THE MSI LOOP AND
POSITION FIXES FROM PGTW AND RJTD WITH POOR CONFIDENCE. THE INITIAL
INTENSITY IS 05 KNOTS HIGHER THAN CONGRUENT ESTIMATES FROM REPORTING
AGENCIES TO REFLECT THE TIGHTER WRAP NOT REFLECTED BY THE DVORAK
TECHNIQUE. UPPER-LEVEL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT WITH
LOW TO MODERATE (10-15 KNOT) VERTICAL WIND SHEAR (VWS) ENHANCED BY
STRONG RADIAL OUTFLOW ESPECIALLY ON THE POLEWARD SIDE. ALONG-TRACK
SEA SURFACE TEMPERATURES (SSTS) ARE ALSO FAVORABLE AT 28-30 DEGREES
CELSIUS. THE CYCLONE IS TRACKING ALONG THE WESTERN PERIPHERY OF A
DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 04W WILL CONTINUE TO TRACK POLEWARD OVER THE NEXT 24 HOURS.
AFTERWARDS, IT WILL ROUND THE STR AND ACCELERATE NORTHEASTWARD AS IT
GETS EMBEDDED IN THE PREVAILING WESTERLIES. THE STORM WILL SEE
MODERATE INTENSIFICATION AS FAVORABLE ENVIRONMENTAL CONDITIONS
PERSIST, PEAKING AT TAU 36-48 DUE INCREASED OUTFLOW FROM ITS INITIAL
EXPOSURE TO THE STRONG WESTERLIES. THIS WILL BE FOLLOWED BY
DETERIORATION AS VWS INCREASES AND SSTS DECREASE.  
   C. AFTER TAU 72, TS LEEPI WILL FURTHER ACCELERATE INTO THE
MID-LATITUDES AND COMMENCE EXTRATROPICAL TRANSITION, BECOMING A
COLD-CORE LOW BY TAU 96. DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT
LENDING HIGH CONFIDENCE TO THE FORECAST WHICH IS INITIALLY LAID
SLIGHTLY RIGHT OF THE MULTI-MODEL CONSENSUS (CONW) THEN FASTER THAN
CONW AFTER TAU 48.  //
NNNN