WDPN31 PGTW 051500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 02W (PENHA) WARNING NR 007// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 8.5N 127.0E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 364 NM WEST-NORTHWEST OF SONSOROL MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 17 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL STORM (TS) 02W (PENHA) WITH A PARTIALLY OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC). CONVECTION HAS CONTINUED TO FLARE IN CLOSE PROXIMITY TO THE LLCC AS THE SOUTHERN AND EASTERN QUADRANTS HAVE REMAINED LARGELY VOID OF ANY SUPPORTIVE CONVECTION. POLEWARD OUTFLOW ALOFT HAS INCREASED OVER THE LAST FEW HOURS, OBSERVED ON ANIMATED ENHANCED WATER VAPOR IMAGERY WITH ASSOCIATED TRANSVERSE BANDING EJECTING INTO THE WESTERN AND NORTHERN SEMICIRCLES. THE ENVIRONMENT HAS REMAINED MARGINALLY FAVORABLE SINCE THE PREVIOUS WARNING, WITH WARM SEA SURFACE TEMPERATURES BETWEEN 28-29 C, ROBUST OUTFLOW ALOFT, AND UNFAVORABLE VERTICAL WIND SHEAR (VWS) OF 25-30 KTS. THE INITIAL POSITION HAS BEEN PLACED WITH MEDIUM CONFIDENCE BASED ON ANIMATED EIR SATELLITE IMAGERY AND EXTRAPOLATION FROM 051223Z METOP-C ASCAT DATA. THE INITIAL INTENSITY HAS BEEN ASSESSED WITH HIGH CONFIDENCE BASED ON A 050942Z RCM-1 SAR PASS. INITIAL WIND RADII BASIS: 050942Z RCM-1 DATA CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTH-NORTHEAST, EXTENDING WESTWARD OVER NORTHERN LUZON AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.5 - 35 KTS KNES: T3.0 - 45 KTS CIMSS ADT: 43 KTS AT 051130Z CIMSS AIDT: 38 KTS AT 051130Z CIMSS D-MINT: 34 KTS AT 050916Z CIMSS D-PRINT: 40 KTS AT 051200Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 25-30 KTS SST: 28-29 CELSIUS OUTFLOW: STRONG POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: HIGH INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 02W IS FORECASTED TO TRACK WEST-NORTHWESTWARD THROUGHOUT THE NEXT 12 HOURS, ALONG THE SOUTHWESTERN EXTENT OF THE STR CENTERED DIRECTLY TO THE NORTH-NORTHEAST. FOLLOWING TAU 12, THE SYSTEM IS EXPECTED TO BEGIN ITS TERMINAL NORTHWEST TRACK THROUGH THE REMAINDER OF THE FORECAST (TAU 48), AS THE STR TO THE NORTH-NORTHEAST RETREATS EASTWARD INTO THE PHILIPPINE SEA. AS THE STR RETREATS EASTWARD, TS 02W WILL TRACK NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE STR UNTIL DISSIPATION OVER WATER AS THE SURFACE VORTEX WEAKENS DUE TO INFLUENCES FROM AN EXPECTED NORTHEASTERN COLD SURGE EVENT THROUGH THE SULU SEA AND WEST PHILIPPINE SEA. REGARDING INTENSITY, TS PENHA IS FORECASTED TO BE NEAR MAXIMUM INTENSITY (40 KTS) NOW BEFORE TOPOGRAPHICAL INTERACTION BEGINS THE SYSTEMS INITIAL WEAKENING PHASE DURING THE NEXT 12 HOURS. DURING THIS PERIOD, TS 02W IS EXPECTED TO BEGIN A GRADUAL DECAY AS MODERATE VWS PERSISTS INTO THE SULU SEA. SURFACE INTENSITIES WILL CONTINUE WEAKENING TOWARD 35 KTS BY TAU 24 WHILE THE NORTHEAST COLD SURGE EVENT PROGRESSES SOUTHWESTWARD INTO THE SULU SEA. AT THIS TIME, A SIGNIFICANT SWATH OF DRY AIR WILL BEGIN ERODING THE SYSTEMS VORTEX FROM THE WEST, ELONGATING THE LLCC THROUGH PERSISTENT NORTHEAST TO SOUTHWEST GRADIENT FLOW AND WEAKENING THE SYSTEM TO 25 KTS BY TAU 48 WITH A LACK OF UPPER-LEVEL OUTFLOW. LASTLY, NORTHEASTERLY GRADIENT FLOW WITH ASSOCIATED DRY AIR WILL LIMIT SUPPORTIVE CONVECTION NEAR THE LLCC, SHALLOWING THE SYSTEM FURTHER AS THE VORTEX OPENS INTO A SURFACE TROUGH WITHIN THE FORECASTED EASTERN EXTENT OF THE NORTHEAST COLD SURGE. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE AND ARTIFICIAL INTELLIGENCE (AI) TRACK GUIDANCE CONTINUES TO REMAIN IN TIGHT AGREEMENT THROUGH THE INITIAL 24 HOURS OF THE FORECAST PERIOD, WITH A 49 NM CROSS-TRACK SPREAD. FOLLOWING TAU 24, NUMERICAL MODEL GUIDANCE BEGINS TO DIVERGE THROUGH THE TERMINAL DISSIPATION PHASE AS TS 02W ENCOUNTERS THE EXPECTED NORTHEAST SURGE EVENT. NAVGEM REMAINS THE ONLY OUTLIER WITH REGARD TO THE FORECASTED TRACK, WITH A NORTHWARD TRACK EXPECTED AFTER TAU 24 UNTIL DISSIPATION. ALL OTHER JTWC TRACK CONSENSUS MEMBERS ILLUSTRATE A GENERALLY NORTHWESTWARD TRACK TOWARD NORTHERN PALAWAN UNTIL TAU 48. THE JTWC TRACK FORECAST HAS BEEN PLACED WITH HIGH CONFIDENCE AND ALIGNED CLOSELY TO THE JTWC MULTI-MODEL CONSENSUS THROUGHOUT THE FORECAST PERIOD. REGARDING INTENSITY, THE MAJORITY OF THE JTWC INTENSITY CONSENSUS MEMBERS CHARACTERIZE A GRADUAL WEAKENING PHASE THROUGHOUT THE FORECAST PERIOD, WITH THE EXCEPTION OF AVAILABLE MESOSCALE SOLUTIONS, SHOWING STEADY INTENSITIES NEAR 35-45 KTS OVER THE NEXT 48 HOURS. DUE TO IMPENDING TOPOGRAPHICAL INTERACTION OVER MINDANAO AND UNFAVORABLE ENVIRONMENTAL CONDITIONS INTRODUCED BY THE NORTHEAST SURGE EVENT, THE JTWC INTENSITY FORECAST HAS BEEN ALIGNED CLOSELY TO THE MULTI-MODEL CONSENSUS THROUGH TAU 24. THE JTWC INTENSITY FORECAST HAS BEEN PLACED BELOW THE JTWC INTENSITY CONSENSUS AFTER TAU 24 AS THE ENVIRONMENT GROWS INCREASINGLY NON-CONDUCIVE, LENDING MEDIUM CONFIDENCE TO THE JTWC INTENSITY FORECAST. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM// NNNN