WDPN32 PGTW 092100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (PEILOU) WARNING NR 012// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 20.5N 145.8E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 411 NM NORTH OF ANDERSEN AFB MOVEMENT PAST 6 HOURS: EASTWARD AT 15 KTS SIGNIFICANT WAVE HEIGHT: 13 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS THE LOW LEVEL CIRCULATION CENTER (LLCC) TROPICAL STORM (TS) 13W (PEILOU) FURTHER OBSCURED BY PERSISTENT CONVECTION CENTERED OVER THE EASTERN FLANK OF THE SYSTEM. A COMPACT CIRCULATION IS SEEN IN A 091620Z AMSR2 89 GHZ MICROWAVE IMAGE AS WELL AS A DEEP BAND OF CONVECTION PARTIALLY WRAPPING ON THE EASTERN AND NORTHERN PERIPHERY. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS WITH WARM (29-30 C) SEA SURFACE TEMPERATURES, LOW (5-10 KTS) VERTICAL WIND SHEAR, AND MODERATE OUTFLOW ALOFT DUE TO A UPPER LEVEL TROUGH SITUATED TO THE NORTHEAST. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE PARTIALLY EXPOSED LOW LEVEL WRAPPING CLOUDS AND REFERENCED MICROWAVE IMAGE. THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON A PARTIAL 091449Z OSCAT IMAGE WITH 30 KTS DISPLACED TO THE SOUTHWEST AS WELL AS THE AGENCY DVORAK FIXES AND OBJECTIVE ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: WIND RADII ADJUSTED BASED ON A 091155Z METOP-C ASCAT IMAGE CURRENT STEERING MECHANISM: LOW-LEVEL MONSOONAL WESTERLIES AND A NEAR EQUITORIAL RIDGE (NER) CENTERED TO THE SOUTHWEST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T1.5 - 25 KTS RCTP: T2.5 - 35 KTS KNES: T2.0 - 30 KTS CIMSS ADT: 37 KTS AT 091730Z CIMSS AIDT: 38 KTS AT 091730Z CIMSS D-MINT: 35 KTS AT 091700Z CIMSS D-PRINT: 32 KTS AT 091900Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE EASTWARD OTHER FACTORS: UPPER LEVEL TROUGH POSITIONED CLOSELY TO THE NORTHWEST ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: HIGH INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 13W IS FORECAST TO TRACK EASTWARD UNTIL TAU 12 AND THEN TURN NORTHEASTWARD AS IT FOLLOWS THE STEERING INFLUENCE OF BOTH A NEAR EQUATORIAL RIDGE (NER) CENTERED TO THE SOUTHWEST AND THE STRONG LOW-LEVEL MONSOONAL WESTERLIES. IN REGARDS TO INTENSITY, A SLIGHT INTENSIFICATION PERIOD IS FORECAST AS THE UPPER LEVEL TROUGH TO THE NORTHWEST REMAINS FAVORABLY POSITIONED TO PROMOTE INCREASED OUTFLOW ALOFT. FOLLOWING TAU 24 TO 36, A WEAKENING TREND IS EXPECTED AND TS 13W IS FORECAST TO ULTIMATELY DISSIPATE BY TAU 60 AS IT EXPERIENCES DRY AIR ENTRAINMENT AND THE UPPER LEVEL TROUGH ULTIMATELY PASSES OVER THE SYSTEM INHIBITING OUTFLOW, AN OUTCOME SUPPORTED ON ALL GLOBAL DETERMINISTIC MODEL FIELDS. MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT FOR THE REMAINDER OF THE FORECAST PERIOD OF THE GENERAL NORTHEASTWARD TRACK, WITH THE LARGER AREA OF DISAGREEMENT BEING THE TRACK SPEED. DISREGARDING NAVGEM AS TOO SLOW OF AN OUTLIER, THE ALONG TRACK SPEED AT TAU 60 IS 200 NM. THE OFFICIAL JTWC FORECAST TRACK IS PLACED WITH HIGH CONFIDENCE, IN BETWEEN THE MULTI-MODEL CONSENSUS AND AI CONSENSUS TRACKS AND SPEEDS. INTENSITY MODEL GUIDANCE IS IN LESS AGREEMENT AS OUTLIERS OF THE DECAY-SHIPS (GFS AND NAVGEM BASED) PREDICT A STRONG INTENSIFICATION OUT TO TAU 96, WHILE THE REMAINDER OF THE GUIDANCE IS IN BETTER AGREEMENT OF A SHORT TERM INTENSIFICATION FOLLOWED BY A LONGER WEAKENING TREND. THE OFFICIAL JTWC FORECAST INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE FOR THE REMAINDER OF THE FORECAST PERIOD, IN GOOD AGREEMENT WITH THE MULTI-MODEL CONSENSUS IN THE SHORT TERM BEFORE DROPPING BELOW GUIDANCE AS NOT ALL INTENSITY GUIDANCE DEPICTS DISSIPATION BY TAU 60. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH INTENSITY 00-72 HR: MEDIUM// NNNN