WDXS31 PGTW 072100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 19S (GOMBE) WARNING NR 001// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 15.6S 51.3E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 294 NM NORTHEAST OF ANTANANARIVO, MADAGASCAR MOVEMENT PAST 6 HOURS: WESTWARD AT 05 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A MEDIUM-SIZED, FAIRLY SYMMETRICAL SYSTEM WITH MINIMAL RAIN BANDS THAT HAS SIGNIFICANTLY DEEPENED AS IT IS ABOUT TO MAKE LANDFALL OVER NORTHEASTERN MADAGASCAR. THE INITIAL INTENSITY IS BASED WITH MEDIUM CONFIDENCE ON A PARTLY EXPOSED LOW LEVEL CIRCULATION FEATURE IN THE 071810Z AMSU-B MICROWAVE IMAGE. THE INITIAL INTENSITY OF 35KTS IS HELD SLIGHTLY HIGHER THAN THE 30-KT MAX INTENSITY INDICATED IN THE 071456Z SMAP PASS AND MORE IN LINE WITH THE FMEE DVORAK ESTIMATE OF T2.5. ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH LOW TO MODERATE (15-2OKT) VWS, MODERATE RADIAL, OUTFLOW, AND WARM SST OFFSET BY LAND INTERACTION WITH MADAGASCAR. THE CYCLONE IS TRACKING SLOWLY ALONG THE NORTHERN PERIPHERY OF THE STR TO THE SOUTH. INITIAL WIND RADII BASIS: SMAP DATA. CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE SOUTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS FMEE: T2.5 - 35 KTS FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 15-20 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY. FORECAST DISCUSSION: TC GOMBE WILL MAKE LANDFALL OVER THE NEXT FEW HOURS, TRACK WEST-NORTHWESTWARD UNDER THE STEERING STR, EXIT INTO THE MOZAMBIQUE CHANNEL BY TAU 36, DRIFT WEST-SOUTHWESTWARD, THEN SOUTHWARD BY TAU 96 AS IT ROUNDS THE WESTERN EDGE OF THE STR AXIS. INTERACTION WITH THE RUGGED TERRAIN ACROSS NORTHERN MADAGASCAR WILL WEAKEN THE CYCLONE DOWN TO 30KTS UP TO TAU 36. AFTERWARD, THE WARM SST IN THE MOZAMBIQUE CHANNEL PLUS CONTINUED FAVORABLE VWS AND OUTFLOW WILL FUEL STEADY INTENSIFICATION TO A PEAK OF 65KTS BY TAU 96. AFTERWARD, INCREASING VWS WILL OFFSET THE OTHER DYNAMICS AND WEAKEN THE CYCLONE DOWN TO 45KTS BY TAU 120. MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL GOOD AGREEMENT BUT GIVEN THE UNCERTAINTIES IN THE INITIAL TRACK OVER LAND, THERE IS OVERALL MEDIUM CONFIDENCE IN THE JTWC TRACK FORECAST. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN