WDPN31 PGTW 121500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 04W (SINLAKU) WARNING NR 015// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 11.1N 150.2E INITIAL INTENSITY: 150 KTS GEOGRAPHIC REFERENCE: 356 NM EAST-SOUTHEAST OF NAVSTA GUAM MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 38 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS SUPER TYPHOON (STY) 04W (SINLAKU) EXHIBITING A HIGHLY AXISYMMETRIC STRUCTURE, CHARACTERIZED BY A NEAR-PERFECTLY SYMMETRIC AND WARM (21 C) 21 NM EYE, ENCIRCLED BY A COHESIVE CENTRAL DENSE OVERCAST. THIS STRUCTURAL PRESENTATION IS A CLEAR INDICATOR OF A RAPID INTENSIFICATION PHASE OCCURRING OVER THE LAST 6 HOURS. ENVIRONMENT ANALYSIS REVEALS A CONTINUOUSLY CONDUCIVE REGIME, INCLUDING SLIGHTLY INCREASED, BUT STILL LOW (10-15 KTS) VERTICAL WIND SHEAR AND WARM (28-29 C) SEA SURFACE TEMPERATURES. FURTHERMORE, EFFICIENT RADIAL OUTFLOW IS BEING DYNAMICALLY ENHANCED BY A FAVORABLE REGIME OF AN UPPER-LEVEL TROUGH TO THE NORTHEAST AND A NEAR-EQUATORIAL RIDGE TO THE SOUTHEAST. AN OTHERWISE DEEPLY MOIST TROPOSPHERIC COLUMN IS BEGINNING TO BE SLIGHTLY DISRUPTED BY DRIER AIR SURROUNDING THE SYSTEM. THE INITIAL POSITION IS PINPOINTED WITH HIGH CONFIDENCE UTILIZING THE SHORTWAVE INFRARED IMAGERY LOOP DEPICTING THE EYE FEATURE. THE INITIAL INTENSITY IS ALSO ESTIMATED WITH HIGH CONFIDENCE AT 150 KTS, A VALUE SUPPORTED BY ALL AGENCY DVORAK INTENSITY ASSESSMENTS AND A CLUSTER OF OBJECTIVE ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT WITH A NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTHEAST AND A SUBTROPICAL RIDGE (STR) TO THE NORTHWEST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T7.5 - 155 KTS RJTD: T7.0 - 140 KTS RCTP: T7.5 - 155 KTS KNES: T7.5 - 155 KTS CIMSS SATCON: 158 KTS AT 121000Z CIMSS ADT: 158 KTS AT 121130Z CIMSS AIDT: 154 KTS AT 121130Z CIMSS D-MINT: 152 KTS AT 120849Z CIMSS D-PRINT: 159 KTS AT 121300Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 28-29 CELSIUS OUTFLOW: STRONG RADIAL OTHER FACTORS: SOME DRIER AIR IS BEGINNING TO WRAP INTO THE OTHERWISE TIGHT CIRCULATION ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH 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 FORECAST TRACK POSITION HAS ONCE AGAIN SHIFTED SLIGHTLY TOWARDS THE ISLAND OF SAIPAN. STY SINLAKU IS CURRENTLY ACCELERATING NORTHWESTWARD AS INDICATED BY ALL AVAILABLE MODEL GUIDANCE. WHILE THE ENVIRONMENT REMAINS HIGHLY FAVORABLE, A FEW MITIGATING FACTORS ARE CURRENTLY BEING INTRODUCED INTO THE OVERALL PICTURE: SURROUNDING DRY AIR IS BEGINNING TO WRAP INTO THE OUTER EDGES OF THE EYEWALL, AND VERTICAL WIND SHEAR IS MARGINALLY INCREASING AND IS EXPECTED TO REACH A MODERATE STRENGTH OF 15-20 KTS WITHIN THE NEXT 24 HOURS. ADDITIONALLY, THE CIMSS MPERC HOVMULLER DIAGRAMS INDICATE A HIGH PROBABILITY FOR EYEWALL REPLACEMENT CYCLE PROCESS TO INITIATE. GLOBAL MODELS INDICATE THAT THE INITIAL PHASE OF WEAKENING WILL ALSO COINCIDE WITH A DECREASING 200MB DIVERGENCE AS THE SYSTEM MOVES SLIGHTLY AWAY FROM THE ENHANCED OUTFLOW CHANNEL PROVIDED BY THE UPPER-LEVEL TROUGH. AS A RESULT, THE SYSTEM HAS EITHER ALREADY REACHED PEAK INTENSITY OR WILL REACH 155-160 KTS WITHIN THE NEXT 6 HOURS. AFTERWARDS, A STEADY, BUT VERY SLOW WEAKENING IS EXPECTED TO INITIATE, WITH MAXIMUM INTENSITY OF 135-140 KTS EXPECTED DURING CPA TO THE NORTHERN MARIANAS. DUE TO THE EXPANSIVE WIND FIELD, GALE-FORCE WINDS ARE EXPECTED TO BEGIN IMPACTING THE MARIANA ISLANDS SHORTLY AROUND TAU 24. AFTER TAU 36, STY 04W WILL CONTINUE TO BE STEERED BY A NORTHWARD-BUILDING EXTENSION OF THE NEAR-EQUATORIAL RIDGE AND BEGIN ITS RECURVATURE AROUND THE RIDGE PERIPHERY, WHILE ENCOUNTERING INCREASING VERTICAL WIND SHEAR AND DRY AIR ENTRAINMENT RESULTING IN FURTHER AND A SLIGHTLY ACCELERATED WEAKENING. MODEL DISCUSSION: CONFIDENCE IN THE TRACK FORECAST IS FAIR AS DYNAMICAL MODELS CONVERGE ON A SCENARIO WHERE THE NORTHWARD-BUILDING NEAR-EQUATORIAL RIDGE BECOMES THE PRIMARY STEERING MECHANISM, FAVORING A CONSISTENT RECURVATURE. HOWEVER, LONG-RANGE TRACK CONFIDENCE REMAINS LOW DUE TO A PERSISTENT 200 NM CROSS-TRACK SPREAD AROUND TAU 96, EXCLUDING THE OUTLIER, NAVGEM, WHICH WOULD OTHERWISE EXTEND THE CROSS-TRACK SPREAD ENVELOPE TO NEARLY 400 NM. NEAR-TERM TRACK GUIDANCE CONFIDENCE IS HIGHER, HOWEVER NAVGEM REMAINS THE MAJOR OUTLIER, WITH ITS TRACK SOUTHWEST OF ROTA. ALL OF THE OTHER MODELS REMAIN CONTAINED WITHIN A 44 NM CROSS-TRACK SPREAD ENVELOPE CENTERED OVER THE ISLAND OF SAIPAN. THE OFFICIAL JTWC TRACK FORECAST FOLLOWS THE MULTI-MODEL CONSENSUS AND IS ONLY OFFSET NORTHEASTWARD, ACCOUNTING FOR THE HIGHER CONFIDENCE IN THE ENVELOPE ASSOCIATED WITH THE DOMINANT GUIDANCE GROUPING. WITH RESPECT TO INTENSITY, THE OFFICIAL FORECAST REMAINS ALIGNED CLOSELY WITH THE HAFS SOLUTION AND IS SET SLIGHTLY ABOVE THE MULTI-MODEL MEAN WITH MEDIUM CONFIDENCE. THIS IS MORE AGGRESSIVE THAN MOST GLOBAL MODELS, ESPECIALLY BEYOND TAU 36. THE OVERALL RI SIGNAL HAS NEARLY COMPLETELY DIMINISHED AT THIS POINT, STRONGLY SUGGESTING THAT STY 04W IS APPROACHING ITS MAXIMUM POTENTIAL INTENSITY OR HAS ALREADY ACHIEVED IT. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN