WDIO31 PGTW 090300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 06B (MANDOUS) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 10.9N 81.4E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 145 NM SOUTH-SOUTHEAST OF CHENNAI, INDIA MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP CONVECTION OVER THE SOUTHWESTERN PERIPHERY OF AN ASSESSED LOW LEVEL CIRCULATION (LLC) TRACKING WEST-NORTHWEST OVER THE SOUTHERN BAY OF BENGAL. AN 082142Z 89 GHZ GMI PASS SHOWS FRAGMENTED BANDING IN THE WESTERN AND SOUTHERN QUADRANTS WRAPPING INTO THE CENTER OF THE LLC. THIS PASS ALSO INDICATES A MAJORITY OF THE CONVECTIVE ACTIVITY TO BE IN THE SOUTHERN PERIPHERY. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE PGTW AGENCY POSITION FIX, ALONG WITH THE AFOREMENTIONED EIR DATA. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON PGTW DVORAK ESTIMATES OF T3.5, IN ADDITION TO ADT WHICH SHOWS 53 KTS. ENVIRONMENTAL ANALYSIS INDICATES TC 06B IS IN A MARGINAL AREA FOR FURTHER DEVELOPMENT WITH MODERATE UPPER-LEVEL OUTFLOW, AND WARM (28-29 C) SEA SURFACE TEMPERATURES, OFFSET BY STRONG (20-25 KTS) VERTICAL WIND SHEAR (VWS). INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS CIMSS ADT: 53 KTS AT 082115Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 20-25 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE POLEWARD 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: TC 06B MANDOUS IS EXPECTED TO CONTINUE TO TRACK NORTHWESTWARD AND MAKE LANDFALL TO THE SOUTHWEST OF CHENNAI ALONG THE COAST OF SOUTHEAST INDIA. THE INTENSITY WILL STEADILY DECREASE TO 45 KNOTS BY TAU 12 DUE TO MODERATE TO STRONG VERTICAL WIND SHEAR (VWS) IN ADDITION TO TERRAIN INFLUENCE. BY TAU 24 TC 06B WILL MAKE LANDFALL AND MOVE INLAND AND CONTINUE TO DECREASE IN INTENSITY AND BEGIN DISSIPATION DUE TO LAND INTERACTION. BY TAU 36 THE SYSTEM IS EXPECTED TO BE DISSIPATED WITH THE INTESNITY FALLING TO 25 KNOTS. MODEL DISCUSSION: THE JTWC TRACK CONSENSUS ENVELOPE CONTINUES TO BE RELATIVELY TIGHT AIMING NORTHWESTWARD WITH A GRADUAL SPREAD TO 40 NM BY TAU 12, INCREASING TO 80 NM AFTER LANDFALL BY TAU 24. DUE TO THE OVERALL GOOD CONFIDENCE IN MODEL TRACK GUIDANCE THE JTWC FORECAST TRACK IS SET CLOSE TO THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS IN BETTER AGREEMENT THAN THE PREVIOUS MODEL RUN WITH A 5-10 KNOT SPREAD AT TAU 12 ASIDE FROM DECY SHIPS WHICH REMAINS AN OUTLIER. THEREFORE, THE JTWC INTENSITY FORECAST IS SET CLOSE TO CONSENSUS AND PLACED WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH INTENSITY 0 - 72 HR: MEDIUM// NNNN