WDPN31 PGTW 190300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (LEEPI) WARNING NR 
06//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 04W (LEEPI), LOCATED APPROXIMATELY 329 NM SOUTH-
SOUTHWESTWARD OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTH-
NORTHWESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED 
MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS DEEP CONVECTIVE BANDING 
WRAPPING INTO A POORLY DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC). 
THE INITIAL POSITION IS BASED ON A 182351Z AND A 182110Z SSMIS 
MICROWAVE IMAGE WITH POOR CONFIDENCE. THE MICROWAVE IMAGES REVEAL 
THAT THE CONVECTIVE BANDING HAS BECOME FRAGMENTED SURROUNDED THE 
LLCC, MAKING IDENTIFICATION OF THE CENTER POSITION AND FIXING 
DIFFICULT. THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS BASED ON 
DVORAK INTENSITY ESTIMATES FROM PGTW AND RJTD. UPPER-LEVEL ANALYSIS 
INDICATES A FAVORABLE ENVIRONMENT WITH SLIGHTLY INCREASING, BUT 
STILL MODERATE (10-20 KNOT) VERTICAL WIND SHEAR (VWS) ENHANCED BY 
STRONG RADIAL OUTFLOW. ALONG-TRACK SEA SURFACE TEMPERATURES (SSTS) 
ARE ALSO FAVORABLE AT 28-30 DEGREES CELSIUS. TS 04W CONTINUES TO 
TRACK 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 18 HOURS. 
IT WILL THEN ROUND THE STR AND ACCELERATE NORTHEASTWARD AS IT 
BECOMES EMBEDDED IN THE PREVAILING WESTERLIES. DUE TO REBESTING THE 
18/18Z POSITION FURTHER TO THE NORTHWEST FROM ITS ORIGINAL POSITION 
ALONG WITH SELECTING A BEST TRACK POSITION FOR 19/00Z IN THE SAME 
DIRECTION, THE OBJECTIVE AIDS AND MULTI-MODEL CONSENSUS (CONW) 
INDICATE A BROADER RECURVE TRACK THAN PREVIOUSLY INDICATED. 
SUBSEQUENTLY, THE CURRENT FORECAST TRACK TAKES A WIDER RECURVE TO 
THE WEST OF KADENA AB THAN THE PREVIOUS FORECAST. TS 04W WILL 
EXPERIENCE MODERATE INTENSIFICATION AS FAVORABLE VWS AND SSTS 
PERSIST. PEAK INTENSIFICATION IS EXPECTED AT APPROXIMATELY TAU 36, 
AS THE SYSTEM COMPLETES THE TURN AROUND THE STR AND EXPERIENCES 
INCREASED OUTFLOW FROM INITIAL EXPOSURE TO THE STRONG WESTERLY 
WINDS. INCREASING VWS AND DECREASING SSTS WILL LEAD TO THE 
DETERIORATION OF THE SYSTEM SOON AFTER. AFTER TAU 48, TS 04W WILL 
FURTHER ACCELERATE INTO THE MID-LATITUDES AND COMMENCE EXTRATROPICAL 
TRANSITION, BECOMING A COLD-CORE LOW BY TAU 72. DYNAMIC MODEL 
GUIDANCE CONTINUES TO BE IN TIGHT AGREEMENT, LENDING HIGH CONFIDENCE 
TO THE FORECAST TRACK, WHICH IS INITIALLY LAID SLIGHTLY RIGHT OF 
CONW AND THEN FASTER THAN CONW AFTER TAU 36.//
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