WDPN31 PGTW 210300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING NR 01// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 11.2N 147.4E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 210 NM SOUTHEAST OF ANDERSEN AFB MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 9 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH DEEP CONVECTIVE BURSTS OVER THE CENTER AND PERSISTENT CONVECTIVE BANDING DISPLACED OVER THE EASTERN AND NORTHERN SEMICIRCLES. A 202341Z MHS 89GHZ MICROWAVE IMAGE INDICATES FRAGMENTED, FORMATIVE BANDING PRIMARILY OVER THE NORTHERN SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE MSI AND LOW-LEVEL CLOUD LINES OVER THE SOUTHERN QUADRANT WRAPPING INTO THE EASTERN QUADRANT. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PGTW DVORAK ESTIMATE OF T2.0, CONSISTENT WITH THE OVERALL STRUCTURE. THE UPPER-LEVEL ENVIRONMENT IS MARGINALLY FAVORABLE DUE TO THE WEAK POLEWARD OUTFLOW INTO A NARROW, WEAK TUTT POSITIONED TO THE NORTH. THIS IS OFFSET SOMEWHAT BY WARM SST VALUES AND LOW VERTICAL WIND SHEAR. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS KNES: T1.5 - 25 KTS FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: WEAK POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE AND SETS THE FORECAST PHILOSOPHY. FORECAST DISCUSSION: TD 06W IS FORECAST TO TRACK AROUND THE SOUTHWEST PERIPHERY OF THE DEEP-LAYERED STR THEN POLEWARD THROUGH THE REMAINDER OF THE FORECAST PERIOD. THE SYSTEM SHOULD SLOW SLIGHTLY AS IT ROUNDS THE STR THEN ACCELERATE AS IT APPROACHES A SHORTWAVE TROUGH EXPECTED TO DIG SOUTH OF HONSHU. DUE TO THE WEAK OUTFLOW AND FORMATIVE LOW-LEVEL CONVECTIVE STRUCTURE, THE SYSTEM WILL INTENSIFY SLOWLY AS IT APPROACHES GUAM WITH A SLIGHT INCREASE IN INTENSITY TO 35 KNOTS BY TAU 24 THEN GRADUAL INTENSIFICATION TO A PEAK OF 45 KNOTS BY TAU 72. AFTER TAU 72, THE SYSTEM WILL WEAKEN DUE TO INCREASING NORTHERLY VERTICAL WIND SHEAR ASSOCIATED WITH THE UPPER-LEVEL STR TO THE NORTHWEST AND A TUTT CELL FORECAST TO TRACK SOUTHEAST OF HONSHU BY TAU 72. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE, IN GENERAL, SUPPORTS THE FORECAST TRACK JUST SOUTH OF GUAM WITH A SPREAD OF 62NM AT TAU 24. THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS BUT SLIGHTLY POLEWARD TOWARD THE ECMF AND EEMN SOLUTIONS, WHICH ARE ON THE NORTHERN EDGE OF THE AIDS ENVELOPE. THE PRIMARY REASON FOR THIS ADJUSTMENT IS THAT THE ECMF AND EEMN INITIALIZED THE SYSTEM CENTER BETTER THAN GFS, WHICH WAS A BIT FURTHER SOUTH. AFTER TAU 24, THE BULK OF THE GUIDANCE REMAINS IN CLOSE AGREEMENT WITH THE JTWC FORECAST TRACK WITH THE EXCEPTION OF THE UKMO ENSEMBLE MEAN AND THE GFS TRACKERS, WHICH DIVERGE SIGNIFICANTLY ON THE WESTERN AND EASTERN SIDES OF THE AIDS ENVELOPE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: HIGH INTENSITY 72-120 HR: MEDIUM// NNNN