WDPN31 PGTW 292100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (NALGAE) WARNING NR 012// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 15.8N 120.2E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 86 NM NORTH-NORTHWEST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 13 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: THE TRACK OF TROPICAL STORM 26W (NALGAE) HAS BEEN UPDATED TO REFLECT PASSAGE TO THE EAST OF MANILA VICE THE WEST, OVER THE PAST 12 HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A RELATIVELY DISORGANIZED PRESENTATION AT THE MOMENT, WITH DETERMINATION OF THE CENTER BEING CHALLENGING AT BEST. BASED ON SURFACE OBSERVATIONS AND ANIMATED PAGASA RADAR IMAGERY, THE LOW LEVEL CIRCULATION CENTER (LLCC) IS ASSESSED TO HAVE FOLLOWED THE TERRAIN FEATURES, PASSED EAST OF MANILA AND THEN TRACKED UP THE EAST SIDE OF THE ZAMBALES MOUNTAINS. THE MOST RECENT OBSERVATIONS SUGGEST THE LLCC IS POSITIONED JUST SOUTH OF DAGUPAN, ABOUT TO EMERGE BACK INTO THE SOUTH CHINA SEA (SCS). BUT DUE TO THE LACK OF A DISTINCT RADAR PRESENTATION AND NO LLCC EVIDENT IN THE EIR, THE INITIAL POSITION IS ASSESSED WITH LOW CONFIDENCE. INTENSITY ESTIMATES SHOW A WIDE SPREAD, WITH PGTW OVER LAND, BUT KNES AND RJTD CAME IN WITH A T3.0 CURRENT INTENSITY ESTIMATE, AND THE CIMSS OPEN-AIIR TECHNIQUE REPORTED A 43 KNOT INTENSITY ESTIMATE AT 1800Z. THE ADT AND SATCON ARE UNREALISTICALLY HIGH, AS THEY ARE FOLLOWING THE PREVIOUS FORECAST INTERPOLATION, AND ARE POSITIONED WELL TO THE SOUTHWEST OF THE ACTUAL POSITION. MEAN SEA-LEVEL PRESSURE READINGS FROM CLARK AIR BASE AND DAGUPAN BOTTOMED OUT AROUND 991MB WHICH SUPPORTS THE 45 KNOT INITIAL INTENSITY WITH HIGH CONFIDENCE. THE ENVIRONMENT REMAINS MARGINALLY FAVORABLE, WITH LOW VWS, AND DECENT POLEWARD AND EQUATORWARD OUTFLOW, BUT THE TIME OVER LAND HAS ROBBED THE SYSTEM OF ENERGY AND ERODED THE LOW-LEVEL CORE. ONCE BACK OVER WATER, THE ENVIRONMENT IS EXPECTED TO QUICKLY IMPROVE HOWEVER. THE SYSTEM IS MOVING ALONG THE LOCALIZED TERRAIN FEATURES AND IS CURRENTLY DECOUPLED FROM THE DEEP-LAYER STEERING RIDGE, BUT AGAIN, AS IT MOVES BACK OVER WATER THE SUBTROPICAL RIDGE (STR) WILL RESUME STEERING. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SOUTHWEST PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE EAST, AND LOCALIZED TERRAIN FEATURES. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: NO CURRENT ESTIMATE RJTD: T3.0 - 45 KTS KNES: T3.0 - 45 KTS CIMSS SATCON: 54 KTS AT 291745Z CIMSS ADT: 57 KTS AT 291730Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 10-15 KTS SST: OVER LAND OUTFLOW: MODERATE POLEWARD AND EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: HIGH INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: HAVING MOVED UP THE CENTRAL PLAINS OF LUZON, ALONG THE EAST SIDE OF THE ZAMBALES RANGE, TS 26W IS CURRENTLY MOVING BACK OVER WATER TO THE WEST OF THE LINGAYAN GULF. THE SYSTEM IS EXPECTED TO TRACK GENERALLY WESTWARD FOR THE NEXT 12 TO 18 HOURS AS IT CONTINUES TO RECONSOLIDATE. AS IT CONSOLIDATES AND INTENSIFIES, THE STEERING LEVEL INCREASES AND THE TRACK IS EXPECTED TO TURN POLEWARD AFTER TAU 24 AS THE SYSTEM MOVES UP THE WEST SIDE OF THE DEEP-LAYER STEERING RIDGE TO THE EAST. A RELATIVELY WEAK MID-LATITUDE TROUGH MOVING QUICKLY TO THE EAST IN ZONAL FLOW WILL PASS BY TO THE NORTH AROUND TAU 36, INDUCE A WEAKNESS IN THE STEERING RIDGE, AND ALLOW TS 26W TO TRACK TOWARDS THE WEAKNESS THROUGH 48. AFTER EMERGING BACK OVER WATER AND MOVING AWAY FROM THE INFLUENCE OF TERRAIN, IT IS EXPECTED THAT TS 26W WILL FAIRLY QUICKLY REESTABLISH ITS LOW-LEVEL CORE STRUCTURE AND BEGIN TO INTENSIFY, THOUGH ONLY SLOWLY AT FIRST. AFTER ABOUT TAU 12, INTENSIFICATION IS EXPECTED TO PICK UP AS THE UPPER-LEVEL PATTERN BECOMES MORE FAVORABLE, SHEAR REMAINS LOW, AND SSTS REMAIN WARM. THE SYSTEM IS EXPECTED TO PEAK AT 70 KNOTS BY 48. AS THE SYSTEM INTENSIFIES, IT WILL PUMP WARM AIR POLEWARD ON THE EASTERN SIDE, INTO THE WESTERN SIDE OF THE STEERING RIDGE AND THIS WILL IN TURN BUILD THE RIDGE TO THE NORTH OF THE SYSTEM. THIS EFFECT IS MOST CLEARLY SEEN IN THE ECMWF AND TO A LESSER EXTENT IN GFS. AFTER REACHING THE PEAK INTENSITY AT TAU 48, SSTS BEGIN TO DECREASE, SHEAR BEGINS TO PICK UP, AND THE SYSTEM BEGINS TO ENTRAIN RELATIVELY LOW THETA-E AIR, CURRENTLY LURKING ALONG THE COAST OF CHINA, INTO THE CORE OF THE SYSTEM. THE SYSTEM WILL BEGIN TO RAPIDLY WEAKEN AFTER TAU 48, AND AS IT DOES SO, WILL TURN TO A WESTWARD TRAJECTORY AS IT COMES UNDER THE INCREASING INFLUENCE OF THE LOW-LEVEL FLOW FROM THE NORTH. BY THE END OF THE FORECAST, THE SYSTEM IS FORECAST TO BE A MINIMAL TROPICAL DEPRESSION SOUTH OF HONG KONG. MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE CONCUR ON THE OVERALL TRACK SCENARIO, THOUGH THE ENSEMBLES STILL SHOW A FAIRLY WIDE SPREAD IN POSSIBLE SOLUTIONS. THE DETERMINISTIC CONSENSUS MEMBERS, WITH THE EXCEPTION OF GALWEM, ARE IN TIGHT AGREEMENT, WITH THE ENVELOPE GRADUALLY EXPANDING FROM 50NM AT TAU 36 TO 110NM AT TAU 72. THE ENVELOPE EXPANDS SIGNIFICANTLY AFTER TAU 72 HOWEVER, AS THE MODELS WEAKEN THE VORTEX AT DIFFERING TIMES AND THUS TURN THE SYSTEM WEST AT VARIOUS POINTS AND TIMES. ACROSS-TRACK SPREAD INCREASES TO A MAXIMUM OF 555NM AT TAU 120 BETWEEN THE ECMWF AND THE GALWEM OUTLIERS. THE BULK OF THE CONSENSUS MEMBERS HOWEVER ARE CONTAINED WITHIN A 250NM WINDOW CONCENTRATED TO THE SOUTH OF HONG KONG. THE JTWC FORECAST LIES WEST AND SOUTH OF THE CONSENSUS MEAN, MOSTLY CLOSELY TRACKING THE GFS ENSEMBLE MEAN, WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE HAS IMPROVED SINCE THE PREVIOUS RUN, WITH ALL OF THE RELIABLE MEMBERS CONSTRAINED WITHIN A 20 KNOT ENVELOPE WITH A PEAK BETWEEN 55-75 KNOTS. THE ENSEMBLE INTENSITY PROBABILITY DATA FOR GEFS AND COAMPS-TC ENSEMBLE SUPPORT A HIGH PROBABILITY OF MODERATE INTENSIFICATION THROUGH TAU 48 AND A 30 PERCENT CHANCE OF RAPID INTENSIFICATION (RI). THE JTWC FORECAST LIES ON THE HIGHER END OF ENVELOPE AND ABOUT FIVE KNOTS HIGHER THAN THE CONSENSUS MEAN, WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN