WDPN32 PGTW 230300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (MEARI)// /WARNING NR 06// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL STORM (TS) 07W (MEARI), LOCATED APPROXIMATELY 410 NM EAST OF MANILA, PHILIPPINES, HAS TRACKED NORTH-NORTHWESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON ANIMATED MULTISPECTRAL SATELLITE IMAGERY AND A 222114Z SSMIS IMAGE. THE LOW LEVEL CIRCULATION OF TS 07W REMAINS ELONGATED, WITH MULTIPLE SMALL-SCALE VORTICES DEVELOPING AND ROTATING AROUND THE CENTER. DEEP CONVECTION CONTINUES TO CYCLICALLY DEVELOP AND WANE NEAR THESE VORTICES, THE MOST PROMINENT OF WHICH NOW LIES TO THE NORTH OF THE BROADER CIRCULATION CENTER. THE CURRENT INTENSITY OF 40 KNOTS IS CONSISTENT WITH RECENT DVORAK T-NUMBER ESTIMATES AND CONVECTIVE STRUCTURE EVIDENT IN RECENT MICROWAVE SATELLITE IMAGERY. TS 07W HAS TRACKED NORTHWESTWARD OVER THE PAST 12 HOURS UNDER THE INFLUENCE OF A SUBTROPICAL STEERING RIDGE TO THE NORTHEAST. 3. FORECAST REASONING. A. THE FORECAST TRACK HAS BEEN SHIFTED EASTWARD SINCE THE PREVIOUS ISSUANCE OF THE PROGNOSTIC REASONING MESSAGE. TS 07W IS NOW EXPECTED TO UNDERGO EXTRATROPICAL TRANSITION VICE DISSIPATION, ALTHOUGH THE SYSTEM WILL WEAKEN DURING THE TRANSITION. B. TS 07W IS EXPECTED TO ROUND THE AXIS OF THE STEERING RIDGE AHEAD OF AN APPROACHING MID-LATITUDE TROUGH DURING THE FORECAST PERIOD. AS THE SYSTEM MOVES POLEWARD, IT WILL ENCOUNTER INCREASING VERTICAL WIND SHEAR AND SUBSIDENCE ALOFT, INTRODUCED BY AN UPPER LEVEL LOW TO THE NORTH, AND THE LOW LEVEL CIRCULATION WILL STRUGGLE TO CONSOLIDATE. HOWEVER, EQUATORWARD OUTFLOW ALOFT IS EXPECTED TO REMAIN STRONG AND THE SYSTEM WILL PASS OVER VERY WARM WATER FOR AT LEAST THE NEXT 48 HOURS. TS 07W SHOULD SLOWLY INTENSIFY UNDER THESE COMPETING INFLUENCES BEFORE PASSING OVER COOLER WATER AND ENCOUNTERING STRONGER VERTICAL WIND SHEAR AHEAD OF AN APPROACHING MID-LATITUDE TROUGH BY TAU 72. THE CURRENT TRACK FORECAST IS IN GOOD AGREEMENT WITH THE MAJORITY OF THE NUMERICAL MODEL GUIDANCE IN THE NEAR TO MEDIUM TERM, INCLUDING THE LATEST ECMWF, JGSM, UKMET, AND GFS RUNS. THE NOGAPS AND GFDN MODELS CONTINUE TO DEPICT A TRACK A BIT FARTHER TO THE EAST, A SCENARIO DEEMED UNLIKELY GIVEN THE MAJORITY OF THE MODEL GUIDANCE AND CURRENT SYNOPTIC REASONING. HOWEVER, INTERACTION BETWEEN TS 07W AND THE UPPER LEVEL LOW TO THE NORTH COULD RESULT IN A SLIGHT EASTWARD DEFLECTION OF THE TRACK, THOUGH ANY INTERACTION BETWEEN THE CIRCULATIONS SHOULD BE LIMITED IF TS 07W REMAINS A WEAK AND RELATIVELY SHALLOW SYSTEM AS FORECAST. C. TS 07W IS EXPECTED TO ACCLERATE INTO THE MID-LATITUDE FLOW PATTERN AND UNDERGO EXTRATROPICAL TRANSITION IN THE EXTENDED FORECAST PERIOD. THE STEERING RIDGE WILL AMPLIFY AHEAD OF A DEVELOPING MID-LATITUDE TROUGH DURING THIS PERIOD, RESULTING IN A MERIDIONAL STEERING PATTERN. INCREASING VERTICAL WIND SHEAR AND PASSAGE OVER COOLER WATER WILL INDUCE PRONOUNCED WEAKENING DURING THIS TRANSITION PERIOD.// NNNN