WDPN31 PGTW 180900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (NOKAEN) WARNING NR 015// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 14.6N 125.5E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 261 NM EAST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 03 KTS SIGNIFICANT WAVE HEIGHT: 16 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM (TS) 01W (NOKAEN) WITH A COMPLETELY EXPOSED AND INCREASINGLY ELONGATED LOW-LEVEL CIRCULATION CENTER (LLCC). ALL ASSOCIATED CONVECTION HAS BECOME DISLOCATED NEARLY 200 NM TO THE NORTH OVER THE LAST FEW HOURS. ENVIRONMENTAL ANALYSIS REVEALS MARGINALLY UNFAVORABLE CONDITIONS, WITH LOW TO MODERATE VERTICAL WIND SHEAR (10-15 KTS), MODERATE POLEWARD OUTFLOW ALOFT, AND EXCESSIVE DRY AIR IN THE MID-LEVELS ENTRAINING INTO THE SYSTEMS VORTEX. THE INITIAL POSITION HAS BEEN PLACED WITH HIGH CONFIDENCE BASED ON ANIMATED MSI IMAGERY. THE INITIAL INTENSITY HAS BEEN ASSESSED WITH MEDIUM CONFIDENCE BASED ON SUBJECTIVE AGENCY DVORAK ESTIMATES AND CIMSS OBJECTIVE INTENSITY ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED DIRECTLY TO THE EAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.0 - 25 KTS RJTD: T2.0 - 30 KTS RCTP: T2.0 - 30 KTS KNES: T1.5 - 25 KTS CIMSS SATCON: 35 KTS AT 180640Z CIMSS ADT: 30 KTS AT 180640Z CIMSS AIDT: 34 KTS AT 180640Z CIMSS D-PRINT: 25 KTS AT 180640Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY UNFAVORABLE VWS: 10-15 KTS SST: 27-28 CELSIUS OUTFLOW: MODERATE POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 01W IS FORECASTED TO TRACK NORTHEASTWARD AROUND THE NORTHWESTERN PERIPHERY OF THE (STR) LOCATED DIRECTLY TO THE EAST OVER THE NEXT 24 HOURS. FOLLOWING TAU 24, THE STR TO THE EAST WILL WEAKEN SUBSTANTIALLY AS AN ADDITIONAL BUILDING STR CENTERED OVER VIETNAM BUILDS EASTWARD ACROSS THE PHILIPPINES. BY TAU 48, THE EASTWARD BUILDING STR WILL BEGIN TO DRIVE TS 01W SOUTHWARD. BETWEEN TAU 48 AND TAU 96, THE WEAK VORTEX WILL BE USHERED SOUTHWARD INTO TOTAL DISSIPATION BY THE STR POSITIONED TO THE WEST. REGARDING INTENSITY, TS 01W IS FORECASTED TO MAINTAIN STEADY SURFACE INTENSITIES BETWEEN 35 KTS AND 40 KTS INTO TAU 48 WITH A RELATIVELY CONDUCIVE ENVIRONMENT OF WARM SEA SURFACE TEMPERATURES (27-28 C), POLEWARD OUTFLOW ALOFT, AND VERTICAL WIND SHEAR (VWS) BELOW 20 KTS. FOLLOWING TAU 48, THE ENVIRONMENT WILL BECOME INCREASINGLY HOSTILE, WITH AMPLIFIED DRY AIR FROM THE WEST AND SUSTAINED VWS BETWEEN 20-30 KTS. SURFACE INTENSITIES ARE FORECASTED TO WEAKEN BETWEEN TAU 48 AND TAU 96, REACHING COMPLETE DISSIPATION BY THE END OF THE FORECAST PERIOD. DURING THIS SAME TERMINAL WEAKENING PHASE, NORTHERLY FLOW THROUGHOUT THE PHILIPPINE SEA WILL MAINTAIN SURFACE INTENSITIES GREATER THAN 25 KTS THROUGHOUT THE SYSTEMS NORTHWEST QUADRANT, HOWEVER, THE DRY AIR ASSOCIATED WITH THE NORTHERLY SURGE WILL FURTHER EXACERBATE DISSIPATION INTO TAU 96 WITHIN THE SYSTEMS CORE. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE REMAINS IN FAIR AGREEMENT DURING THE INITIAL 36 HOURS OF THE FORECAST PERIOD, PRIOR TO THE SYSTEMS FORECASTED TRACK SOUTHWARD BETWEEN TAU 48 AND TAU 96. WHILE THE STR CENTERED OVER VIETNAM BUILDS WESTWARD, NUMERICAL MODEL GUIDANCE AND ARTIFICIAL INTELLIGENCE (AI) SOLUTIONS CHARACTERIZE VARYING TRACK SOLUTIONS THROUGH THE EXPECTED RECURVE SCENARIO. THROUGH THE INITIAL 36 HOURS, THE JTWC TRACK FORECAST IS CLOSELY ALIGNED WITH THE JTWC CONSENSUS PACKAGE, LENDING MEDIUM CONFIDENCE TO THE TRACK FORECAST. FOLLOWING TAU 36, THE RATE OF DISSIPATION BETWEEN JTWC CONSENSUS SOLUTIONS HAS RESULTED IN A WIDE CROSS-TRACK SPREAD, EXCEEDING 600 NM BY TAU 96. THEREFORE, THE JTWC TRACK FORECAST HAS BEEN PLACED WITH LOW CONFIDENCE BASED ON THE VARYING RATES OF TERMINAL WEAKENING AFTER TAU 48 DUE TO THE ADDITIONAL STEERING RIDGE TO THE WEST AND INFLUENCES FROM THE EXPECTED NORTHERLY SURGE EVENT WITHIN THE PHILIPPINE SEA. REGARDING INTENSITY, THE JTWC INTENSITY CONSENSUS PACKAGE REMAINS IN RELATIVELY GOOD AGREEMENT THAT TS 01W WILL MAINTAIN INTENSITIES BETWEEN 35-40 KTS INTO TAU 48. FOLLOWING TAU 48, ALL JTWC INTENSITY CONSENSUS MEMBERS ILLUSTRATE A GRADUAL WEAKENING PHASE UNTIL THE END OF THE FORECAST PERIOD, HOWEVER, ADDITIONAL DRY AIR FROM THE NORTHERLY SURGE EVENT INTO THE SYSTEMS SHALLOW VORTEX WILL DICTATE HOW LONG 25 KTS IS MAINTAINED. THEREFORE, THE INTENSITY FORECAST BETWEEN TAU 48 AND TAU 96 HAS BEEN ASSESSED WITH LOW CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN