WDPN31 PGTW 291500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (NALGAE) WARNING NR 011// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 14.3N 120.8E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 21 NM SOUTH-SOUTHWEST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL STORM 26W IS CURRENTLY LOCATED OVER THE CENTRAL PHILIPPINE ISLAND OF LUZON, VERY CLOSE TO EMERGING BACK INTO THE SOUTH CHINA SEA (SCS), WHILE TRACKING WEST-NORTHWESTWARD OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DISORGANIZED DEEP CONVECTION THAT CONTINUES TO FLARE UP AND OBSCURE THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON MULTI-AGENCY FIX POSITIONS, ALONG WITH THE ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND ANIMATED RADAR IMAGERY. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE A COMBINATION OF OBJECTIVE DVORAK INTENSITY ESTIMATES. ENVIRONMENTAL CONDITIONS ARE CURRENTLY FAVORABLE AND CONDUCIVE FOR DEVELOPMENT WITH LOW (5-10 KNOTS) VERTICAL WIND SHEAR (VWS), WARM (28-29C) SEA SURFACE TEMPERATURES (SSTS), AND GOOD WESTWARD AND EQUATORWARD OUTFLOW INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: NO CURRENT ESTIMATE RJTD: T3.0 - 45 KTS CIMSS ADT: 55 KTS AT 291130Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM 26W HAD SINCE BEEN MOVING OVER THE CENTRAL PHILIPPINE ISLAND OF LUZON, JUST SOUTH OF MANILA, BUT IS FORECAST TO EMERGE BACK INTO THE SCS BY TAU 12. THE SYSTEM WILL CONTINUE TO TRACK WEST-NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE STR TO THE NORTHEAST THROUGH TAU 24. AFTER TAU 24, TS 26W WILL BEGIN TO TURN AND TRACK NORTHWESTWARD AS MODEL GUIDANCE INDICATES THE WESTERN SIDE OF THE STR WILL ERODE AND WEAKEN AHEAD OF AN APPROACHING MID-LATITUDE TROUGH. AS THIS OCCURS TS 26W WILL HOLD STEADY ON A NORTH-NORTHWEST TRACK THROUGH TAU 72. AFTER TAU 72, THE STEERING PATTERN CHANGES ONCE MORE AS THE MID-LATITUDE TROUGH BECOMES MORE ZONAL, ALLOWING THE STR TO THE EAST TO BUILD WESTWARD, WHICH WILL THEN INFLUENCE AND STEER THE SYSTEM SHARPLY TO THE NORTHWEST AND THEN WEST-NORTHWEST THROUGH TAU 120. TS 26W IS FORECAST TO GRADUALLY INTENSIFY OVER THE NEXT 24 HOURS AS THE SYSTEM REEMERGES INTO THE SCS. BETWEEN TAU 36 AND TAU 48 AN UPPER-LEVEL POINT SOURCE ALOFT IS ANTICIPATED TO DEVELOP ALONG WITH WARM SSTS, WHICH WILL ENABLE A PERIOD OF HIGHER INTENSIFICATION, UP TO A PEAK OF 75 KNOTS. HOWEVER, BY TAU 72, COOLING SSTS, INCREASING VERTICAL WIND SHEAR, ALONG WITH DRY AIR ENTRAINMENT WILL LEAD TO A STEADY WEAKENING TREND. ENVIRONMENTAL FACTORS WILL CONTINUE TO DEGRADE LEADING TO TROPICAL DEPRESSION STRENGTH BY TAU 120. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN OVERALL GOOD AGREEMENT ON THE TRACK FORECAST WITH ALL CONSENSUS MODELS IN TIGHT AGREEMENT THROUGH TAU 48. BETWEEN TAU 72 AND TAU 120, TRACK GUIDANCE INCREASES TO A 300NM CROSS-TRACK SPREAD. THE JTWC FORECAST REMAINS CONSISTENT WITH THE PREVIOUS FORECAST THROUGH TAU 48. BETWEEN TAU 72 AND TAU 120 THE TRACK HAS SHIFTED SLIGHTLY TO THE WEST-NORTHWEST AND THE MAJORITY OF THE NUMERICAL MODELS HAVE ALL COME INTO BETTER AGREEMENT. THE ENSEMBLE MEMBERS IN BOTH OF GEFS AND ECENS SHOW A WIDE CROSS-TRACK SPREAD, HOWEVER, BOTH THE ENSEMBLE MEAN'S GENERALLY AGREE ON A SIMILAR OVERALL TRACK THROUGH TAU 120. THEREFORE, THE JTWC TRACK FORECAST IS PLACED WITH MEDIUM CONFIDENCE. THE RELIABLE INTENSITY GUIDANCE REMAINS MIXED, WITH DECAY SHIPS (GFS) REPRESENTING THE HIGH END OF INTENSITY GUIDANCE, WHILE CTCI, COTI REPRESENTS THE LOW END OF INTENSITY GUIDANCE. ADDITIONALLY, GEFS CONTINUES TO SHOW MODEST PROBABILITIES OF MODERATE INTENSIFICATION OVER THE NEXT 48-60 HOURS. THEREFORE, THE JTWC INTENSITY FORECAST IS PLACED WITH MEDIUM CONFIDENCE AND LIES CLOSE TO AND SLIGHTLY ABOVE THE CONSENSUS MEAN. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN