WDPN31 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 04W (LEEPI) 
WARNING NR 10//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 04W (LEEPI), LOCATED APPROXIMATELY 132 NM 
WEST-NORTHWESTWARD OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED 
NORTHWARD AT 16 KNOTS OVER THE PAST SIX HOURS. ANIMATED 
MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A SERIES OF SMALLER 
CIRCULATIONS LOCATED WITHIN A LARGER SCALE TOROIDAL CIRCULATION. THE 
CURRENT POSITION HAS BEEN LOCATED AT THE CENTER OF THE TOROID, 
REFLECTING THE POSITION OF GREATEST TURNING. BASED ON AN OLDER 
191455Z OSCAT PASS SHOWING WIND SPEEDS ON THE ORDER OF 30 KNOTS, THE 
CURRENT INTENSITY HAS BEEN DECREASED TO ACCOUNT FOR THE WEAKENING 
OBSERVED IN MSI. UPPER LEVEL ANALYSIS INDICATES THE ANTICYCLONE 
LOCATED OVER EASTERN CHINA HAS BEEN INTERACTING WITH A TUTT CELL TO 
THE EAST OF TD 04W, CREATING MODERATE TO HIGH LEVELS OF VERTICAL 
WIND SHEAR (VWS) (20 TO 30 KNOTS). THIS INCREASE IN VWS HAS CAUSED 
THE LOW LEVEL TO BECOME FULLY EXPOSED. TD 04W CONTINUES TO TRACK 
NORTHWARD AROUND THE WESTERN PERIPHERY OF A LOW- TO MID-LEVEL 
SUBTROPICAL RIDGE (STR). SEA SURFACE TEMPERATURES (SSTS) REMAIN 
FAVORABLE (28 TO 29 DEGREES CELSIUS). 
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 06 TO 12 
HOURS AROUND THE STR, ROUNDING THE NORTHWESTERN PERIPHERY, AND 
TRANSITIONING TO AN EAST-NORTHEASTWARD TRACK. THE SYSTEM WILL BECOME 
EMBEDDED WITHIN THE MID-LATITUDE WESTERLIES BETWEEN TAU 12 AND 24, 
TRACKING THE LOW LEVEL OVER SOUTHERN KYUSHU INTO THE NORTHERN 
PACIFIC OCEAN. DUE TO THE TRACK OVER LAND, HARSH UPPER LEVEL 
ENVIRONMENT (HIGH LEVELS OF VWS) AND UNFAVORABLE SSTS, THE SYSTEM 
WILL UNDERGO A TRANSITION FROM A WARM-CORE TROPICAL TO A COLD-CORE 
EXTRATROPICAL SYSTEM BY TAU 48. HOWEVER, THERE ARE SOME INDICATIONS 
THIS PROCESS COULD OCCUR MORE RAPIDLY AS IT TRACKS OVER KYUSHU. 
DYNAMIC MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT, LEADING TO HIGH 
CONFIDENCE IN THE FORECAST TRACK.//
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