WDIO31 PGTW 091500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02B (ASANI) WARNING NR 010// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 14.2N 84.7E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 546 NM SOUTH-SOUTHWEST OF KOLKATA, INDIA MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 21 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS INTENSE, FLARING CONVECTIVE BURSTS WITHIN A CENTRAL DENSE OVERCAST (CDO) OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC), WHICH IS POSITIONED UNDER THE NORTHEASTERN EDGE OF THE CDO. A 091224Z SSMIS 91GHZ MICROWAVE IMAGE REVEALS AN AREA OF DISORGANIZED DEEP CONVECTION SHEARED OVER THE WESTERN QUADRANT OF AN EXPOSED, SHALLOW LOW-LEVEL CIRCULATION (LLC). THE 37GHZ IMAGE INDICATES THE LLC REMAINS ORGANIZED WITH SHALLOW BANDING WRAPPING TIGHTLY INTO A DEFINED CENTER, WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. ENVIRONMENTAL CONDITIONS REMAIN MARGINALLY FAVORABLE WITH HIGH (25-30 KNOTS) EASTERLY VERTICAL WIND SHEAR (VWS) OFFSET BY STRONG WESTWARD OUTFLOW. ANIMATED WATER VAPOR IMAGERY INDICATES POLEWARD OUTFLOW HAS EFFECTIVELY CEASED OVER THE PAST TWELVE HOURS. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE PGTW AND DEMS DVORAK CURRENT INTENSITY ESTIMATES AND THE CIMSS ADT ESTIMATE. INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: SOUTHWEST PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS DEMS: T3.5 - 55 KTS CIMSS ADT: 55 KTS AT 091115Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 25-30 KTS SST: 30-31 CELSIUS OUTFLOW: STRONG WESTWARD OTHER FACTORS: DRY AIR ENTRAINMENT IN THE UPPER-LEVELS ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: OVER THE PAST TWO DAYS, THE STR HAS REMAINED ENTRENCHED TO THE NORTHEAST. PREVIOUS MODEL GUIDANCE HAD INDICATED THE STR WOULD ERODE AS A MIDLATITUDE TROUGH DEEPENED TO THE NORTH ALLOWING THE SYSTEM TO RECURVE. UPPER-LEVEL ANALYSIS DOES INDICATE A WEAK TROUGH OVER NORTHEAST INDIA, BARELY DISCERNIBLE IN ANIMATED WATER VAPOR IMAGERY, HOWEVER THE TROUGH IS FORECAST TO PROPAGATE EASTWARD WITH LITTLE EFFECT ON THE STRENGTH OF THE STR. THE CURRENT FORECAST INDICATES THE SYSTEM WILL CONTINUE TO TRACK WEST- NORTHWESTWARD TO NORTHWESTWARD SLOWLY TURNING POLEWARD NEAR VISAKHAPATNAM BY TAU 48 WITHIN A COMPETING STEERING ENVIRONMENT. TC 02B WILL WEAKEN STEADILY DURING THIS PERIOD UNDER PERSISTENT EASTERLY VWS (25-30 KNOTS) AND INTERACTION WITH LAND. AFTER TAU 48, UPPER-LEVEL WESTERLIES ARE EXPECTED TO PUSH INTO THE BAY OF BENGAL WITH THE STR WEAKENING AND SHIFTING EAST. THIS SHOULD ALLOW THE SYSTEM TO ACCELERATE NORTHEASTWARD TOWARD BANGLADESH ALONG THE NORTHWESTERN PERIPHERY OF THE STR. TC 02B WILL BE EMBEDDED WITHIN THE UPPER-LEVEL WESTERLIES IN A MARGINAL ENVIRONMENT WITH DRY AIR ENTRAINING INTO THE SYSTEM OFF THE DECCAN PLATEAU AND IS EXPECTED TO CONTINUE TO WEAKEN AND EVENTUALLY DISSIPATE OVER THE NORTHERN BAY OF BENGAL. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO STRUGGLE WITH THIS COMPLEX STEERING ENVIRONMENT WITH SIGNIFICANT UNCERTAINTY IN THE JTWC FORECAST TRACK. IN GENERAL, MODEL GUIDANCE IS IN POOR AGREEMENT AND SHOWS A LARGE SPREAD IN SOLUTIONS AFTER TAU 24. THE 090600Z ECMWF ENSEMBLE (EPS) STRIKE PROBABILITY PRODUCT, WHICH HAS HANDLED THE SCENARIO FAIRLY WELL THUS FAR, IS NOW INDICATING A BIFURCATION WITH LANDFALL NEAR VISAKHAPATNAM AND DISSIPATION OR A SHARP NORTHEASTWARD RECURVE AND TRACK ALONG THE COAST OF NORTHEAST INDIA AND EVENTUAL DISSIPATION NEAR BANGLADESH. THE BULK OF THE RELIABLE INTENSITY GUIDANCE INDICATES GOOD AGREEMENT ON STEADY WEAKENING WITH A WEAK TROPICAL CYCLONE IN THE EXTENDED PERIOD THUS OVERALL MEDIUM CONFIDENCE. MODEL GUIDANCE DOES INDICATE, HOWEVER, SIGNIFICANT RAINFALL SPREADING ACROSS EASTERN INDIA AND THE NORTHERN BAY OF BENGAL INTO BANGLADESH AND MYANMAR. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN