WDPN32 PGTW 100300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (PEILOU) WARNING NR 013// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 20.5N 148.3E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 452 NM NORTH-NORTHEAST OF ANDERSEN AFB MOVEMENT PAST 6 HOURS: EASTWARD AT 24 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM (TS) 13W (PEILOU) AS A SMALL SYSTEM WITH PERSISTENT CONVECTION JUST NORTHEAST OF THE ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC) AS WELL AS A STRONG CONVECTIVE BAND CURVING OFF TO THE SOUTHWEST, SPANNING ACROSS THE NORTHERN MARIANAS. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS OF LOW (5-10 KTS) VERTICAL WIND SHEAR, WARM (29- 30 C) SEA SURFACE TEMPERATURES, AND AN UPPER-LEVEL TROUGH POSITIONED TO THE NORTHWEST OF TS 13W AIDING IN THE UPPER LEVEL OUTFLOW, OBSERVABLE IN MSI. THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PARTIALLY EXPOSED WESTERN FLANK OF THE LLCC IN MSI. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AGREEMENT BETWEEN AGENCY DVORAK FIXES AND CIMSS OBJECTIVE ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: LOW-LEVEL MONSOONAL FLOW AND EASTERN EXTENSION OF A NEAR EQUATORIAL RIDGE (NER) CENTERED TO THE SOUTHWEST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.0 - 30 KTS RCTP: T2.5 - 35 KTS CIMSS ADT: 43 KTS AT 092330Z CIMSS AIDT: 37 KTS AT 092330Z CIMSS D-PRINT: 31 KTS AT 092330Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG POLEWARD OTHER FACTORS: UPPER-LEVEL TROUGH POSITIONED TO THE NORTHWEST ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 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 CONTINUE ON AN EAST- NORTHEASTWARD TRACK OUT TO TAU 12 BEFORE TAKING A MORE POLEWARD TURN AS IT REMAINS UNDER THE STEERING INFLUENCE OF THE STRONG LOW-LEVEL MONSOONAL FLOW AND, TO A LESSER EXTENT, THE EASTERN EXTENSION OF A NEAR EQUATORIAL RIDGE (NER) CENTERED TO THE SOUTHWEST, WITH BOTH CONTRIBUTING TO THE SAME RESULTANT TRACK. REGARDING INTENSITY, TS 13W IS CURRENTLY IN AN AREA OF INCREASED OUTFLOW ALOFT THANKS TO THE UPPER-LEVEL TROUGH POSITIONED TO THE NORTHWEST, HOWEVER THIS TROUGH IS EXPECTED TO PASS OVER TS 13W AND RETREAT BY TAU 36 AT WHICH POINT THE SYSTEM IS EXPECTED TO EXPERIENCE INCREASED NORTHWESTERLY SHEAR CAUSED BY STRONG UPPER LEVEL WESTERLIES AND ENSUING DRY AIR ENTRAINMENT. THEREFORE, TS 13W IS FORECAST TO BEGIN A WEAKENING TREND AT TAU 24 AND ULTIMATELY DISSIPATE BY TAU 60. MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT FOR THE REMAINDER OF THE FORECAST PERIOD WITH A CROSS TRACK SPREAD OF 140 NM AT TAU 60. MODEL TRACK SPEED HAS ALSO COME INTO BETTER AGREEMENT, WITH THE ONLY OUTLIER OF NAVGEM BEING EXCLUDED AS MUCH SLOWER, ALONG TRACK SPREAD IS 85 NM AT TAU 60. THE OFFICIAL JTWC FORECAST TRACK IS PLACED WITH HIGH CONFIDENCE, IN LINE WITH THE MULTI-MODEL CONSENSUS AND SLIGHTLY FASTER MORE IN ACCORDANCE WITH THE AI CONSENSUS. INTENSITY MODEL GUIDANCE HAS ALSO COME INTO BETTER AGREEMENT WITH DECAY-SHIPS (GFS BASED) REMAINING THE ONLY OUTLIER WITH A GRADUAL INTENSIFICATION TREND OUT TO TAU 96, THE REMAINDER OF GUIDANCE AGREES ON A GENERAL WEAKENING PHASE BEYOND TAU 24. THE OFFICIAL JTWC FORECAST INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, CLOSELY IN LINE WITH THE MULTI-MODEL CONSENSUS OUT TO TAU 36 BUT THEN DIVERGING FROM THE BULK OF GUIDANCE EXPECTING DISSIPATION BY TAU 60, IN LINE WITH ALL GLOBAL DETERMINISTIC MODEL FIELDS WHICH PICTURE TS 13W OPENING INTO A TROUGH BY THAT POINT. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH INTENSITY 00-72 HR: MEDIUM// NNNN