WDPN31 PGTW 150900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 04W (SINLAKU) WARNING NR 026// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 16.0N 144.9E INITIAL INTENSITY: 110 KTS GEOGRAPHIC REFERENCE: 71 NM NORTHWEST OF SAIPAN MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 05 KTS SIGNIFICANT WAVE HEIGHT: 42 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A LARGE, POWERFUL TYPHOON SLOWLY TRACKING AWAY FROM SAIPAN AND TINIAN. THE 4-5 KT FORWARD SPEED HAS LED TO A PROLONGED PERIOD OF DESTRUCTIVE WINDS OVER THE MARIANA ISLANDS. DEEP CONVECTION ASSOCIATED WITH THE CENTRAL DENSE OVERCAST (CDO) CONTINUES TO ROTATE AROUND A LARGE EYE. HAVING COMPLETED AN EYEWALL REPLACEMENT CYCLE (ERC), THE EYE HAS ENLARGED TO 30 NM IN DIAMETER, AND THE WIND FIELD HAS EXPANDED. A 142053Z WSF-M MWI 37 GHZ IMAGE SHOWED AN EYEWALL SLIGHTLY OPEN ON THE NORTHERN SIDE WITH AN EVEN LARGER OUTER RING MEASURING 100-110 NM IN DIAMETER, WHICH SIGNIFIES POTENTIAL FOR ANOTHER ERC. A COINCIDENT 142003Z RCM-3 SAR PASS REVEALED A SIMILAR STRUCTURE WITH A 110 KT AVERAGE PEAK WIND. IN FACT, THE CIMSS MPERC PRODUCT CAPTURES THIS STRUCTURE AND PREDICTS A 77 PERCENT PROBABILITY OF ANOTHER ERC. IN THE PAST 06 HOURS, TY 04W HAS BEEN ATTEMPTING TO CONSOLIDATE ITS INNER CORE AS THE SURROUNDING CLOUD TOPS COOL, AND THE UPPER-LEVEL OUTFLOW EXPANDS RADIALLY. BASED ON THIS TREND, THE INITIAL INTENSITY IS HELD AT 110 KTS WITH MEDIUM CONFIDENCE AND IS CONGRUENT WITH THE AGENCY DVORAK ESTIMATES RANGING FROM T5.5 TO T6.5 AND THE CIMSS SATCON. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE WELL-DEFINED, CIRCULAR EYE ON THE MSI. THE 34 KT WIND RADII WAS EXPANDED IN THE SOUTHWEST QUADRANT TO ACCOUNT FOR THE GALE-FORCE WINDS STILL OBSERVED IN GUAM. ENVIRONMENTAL ANALYSIS INDICATES FAVORABLE CONDITIONS OF WARM SEA SURFACE TEMPERATURES, PLENTIFUL MID-LEVEL MOISTURE, AND LOW VERTICAL WIND SHEAR (VWS). INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: NORTHERN EXTENSION OF THE NEAR-EQUATORIAL RIDGE TO THE SOUTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T6.0 - 115 KTS RJTD: T6.5 - 127 KTS RCTP: T6.5 - 127 KTS KNES: T5.5 - 102 KTS CIMSS SATCON: 114 KTS AT 150600Z CIMSS ADT: 97 KTS AT 150530Z CIMSS AIDT: 99 KTS AT 150630Z CIMSS D-PRINT: 102 KTS AT 150630Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH 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: THE PRIMARY DRIVING MECHANISM FOR TY 04W IS THE NORTHERN EXTENSION OF A NER. THE RIDGE WILL PINCH OFF FROM THE NER AND BUILD, WHICH WILL STEER THE SYSTEM NORTHWARD THROUGH TAU 24. FOR THE REMAINDER OF THE FORECAST PERIOD, THE MID-LATITUDE WESTERLIES WILL INCREASINGLY IMPART A FORCE TOWARDS THE EAST, CAUSING THE STORM TO CURVE AND ACCELERATE NORTH-NORTHEAST FROM TAU 24 TO TAU 72 AND NORTHEAST TO EAST-NORTHEAST TOWARDS THE END OF THE PERIOD. THE INTENSITY FORECAST FOR THE FIRST 24 HOURS HAS BEEN ADJUSTED UPWARD. NOW THAT SINLAKU HAS COMPLETED ERC, THE FAVORABLE ENVIRONMENTAL CONDITIONS WILL HELP MAINTAIN THE INTENSITY. IF A SECOND ERC COMMENCES, IT WOULD SUPPORT CAPPING THE INTENSITY AND POTENTIALLY INDUCE A SLOW WEAKENING TREND. THE INTENSITY FORECAST CAPTURES THIS BY HOLDING THE INTENSITY STEADY THROUGH TAU 12 AND THEN SHOWS SLOW WEAKENING AT TAU 24. TY 04W WILL WEAKEN MORE QUICKLY BETWEEN TAU 24 AND TAU 48 AS IT ENCOUNTERS COOLER WATERS, BECOMES SURROUNDED BY DRIER AIR, AND ENTERTAINS STRONGER POTENTIAL FOR DRY AIR ENTRAINMENT DUE TO A SECOND ERC. RAPID WEAKENING WILL TAKE PLACE AFTER TAU 48 ONCE THE SYSTEM TRAVELS OVER SUB-26 DEGREE CELSIUS SST, AND THE VWS ASSOCIATED WITH THE WESTERLIES INCREASES TO 20-30 KTS. EXTRATROPICAL TRANSITION (ETT) WILL BEGIN AT TAU 72. NEVERTHELESS, THE FORECAST CALLS FOR A POTENT, STORM-FORCE EXTRATROPICAL LOW AT TAU 120. MODEL DISCUSSION: MODELS ARE IN FAIR AGREEMENT WITH A CROSS-TRACK SPREAD OF 45 NM AT TAU 24 AND 120 NM AT TAU 48. NAVGEM IS THE WESTERNMOST TRACKER AND KEEPS THE SYSTEM SOUTHEAST OF IWO TO BY MORE THAN 270 NM, LEADING TO HIGH CONFIDENCE THAT THE ISLAND WILL REMAIN OUTSIDE OF THE GALE-FORCE WIND FIELD. THE FORECAST TRACK IS SIMILAR TO THE PREVIOUS, SHIFTING 20-30 NM NORTHWARD AT TAU 96 AND 120. THE ECMWF, HAFS-A, AND EXPERIMENTAL AI MODELS COMPRISE THE TIGHTEST GROUPING AND ARE CLOSEST TO THE JTWC FORECAST TRACK. NAVGEM, GALWEM, AND THE UKMET MODELS SPAN THE POLEWARD SIDE OF THE GUIDANCE ENVELOPE, WHILE HWRF AND GFS ARE ON THE EQUATORWARD SIDE. THE INTENSITY FORECAST THROUGH TAU 24 IS SET HIGHER THAN ALL BUT THE EXPERIMENTAL AI MODELS AND ECMWF, WHICH APPEAR TO BETTER HANDLE THE RECENT DEVELOPMENT OF TY 04W. COAMPS-TC WEAKEN THE SYSTEM BY 30 KTS IN THE NEXT 12-24 HOURS, WHICH IS DEEMED UNREALISTIC. THE FORECAST IS THEN PLACED CLOSER TO THE CONSENSUS FROM TAU 48 TO TAU 96 AND THEN ALIGNS MORE CLOSELY WITH GFS AS THE SYSTEM BECOMES EXTRATROPICAL. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN