TC 08S(CHENESO): just below Typhoon intensity,forecast landfall near Sambava//TC 09P(IRENE) peaked// Invest 92P: TCFA// 1903utc

JTWC IS ISSUING 6HOURLY WARNINGS ON TC 09P AND 12HOURLY WARNINGS ON TC 08S. 3HOURLY SATELLITE BULLETINS ARE ISSUED ON BOTH SYSTEMS.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A RAPIDLY CONSOLIDATING SYSTEM WITH A CENTRAL DENSE OVERCAST FEATURE OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). THIS IMPROVEMENT IS EVIDENT IN AN 181418Z SSMIS 91GHZ MICROWAVE IMAGE, WHICH REVEALS A COMPACT CORE SURROUNDING A SMALL MICROWAVE EYE FEATURE AND DEEP CONVECTIVE BANDING OVER THE WESTERN SEMICIRCLE. OVERALL ENVIRONMENTAL CONDITIONS ARE FAVORABLE WITH ROBUST POLEWARD OUTFLOW, LOW TO MODERATE VERTICAL WIND SHEAR AND WARM SST VALUES. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE SSMIS IMAGE. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE KNES AND FMEE DVORAK ESTIMATES AS WELL AS A TIMELY 181432Z SMAP IMAGE SHOWING 58 KNOT (1-MINUTE AVERAGE) WINDS OVER THE NORTHERN QUADRANT.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 08S IS TRACKING ALONG THE NORTHERN PERIPHERY OF THE STR AND IS FORECAST TO MAKE LANDFALL OVER NORTHEASTERN MADAGASCAR WITHIN THE NEXT 12 HOURS. DUE TO FAVORABLE CONDITIONS, TC 08S WILL CONTINUE TO INTENSIFY PRIOR TO LANDFALL TO A PEAK OF 60-65 KNOTS. THE STR IS EXPECTED TO REALIGN TO THE EAST WHICH WILL TURN THE SYSTEM SOUTH-SOUTHWESTWARD AS IT TRACKS OVER THE MOUNTAINOUS TERRAIN OF MADAGASCAR. CONSEQUENTLY, THE SYSTEM WILL WEAKEN RAPIDLY AND DISSIPATE BY TAU 36. AFTER TAU 36, THE SYSTEM WILL STALL OVER MADAGASCAR DUE TO COMPETING STEERING INFLUENCES AND WILL CONTINUE TO WEAKEN RAPIDLY.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 24 THEN DIVERGES WITH INCREASING UNCERTAINTY IN THE TRACK. THE MAJORITY OF THE TRACK GUIDANCE KEEPS THE REMNANTS OVERLAND, HOWEVER, THE 181200Z ECMWF (EPS) ENSEMBLE INDICATES SOME POTENTIAL FOR THE REMNANTS TO MOVE BACK OVER WATER AFTER THREE DAYS.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPOSED, BROAD LOW-LEVEL CIRCULATION (LLC) WITH DEEP CONVECTION SHEARED TO THE SOUTHEAST. AN 182136Z MHS 89GHZ MICROWAVE IMAGE INDICATES A CLUSTER OF INTENSE CONVECTION SHEARED TO THE EAST OF AN EXPOSED, WEAKLY DEFINED LLC. AN 182231Z ASCAT-C IMAGE REVEALS AN ELONGATED CIRCULATION WITH 40-45 KNOT WINDS OVER THE EASTERN AND SOUTHERN QUADRANTS. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THIS ASCAT-C IMAGE. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE ASCAT DATA. RECENT SURFACE OBSERVATIONS FROM WHITEGRASS AIRPORT ON THE ISLAND OF TANNA INDICATE SOUTHERLY WINDS AT 10 KNOTS WITH SLP NEAR 996MB. BASED ON THE WIND SHIFT AT WHITEGRASS AIRPORT OVER THE PAST FEW HOURS, THE SYSTEM CENTER IS PASSING DIRECTLY OVER THE ISLAND.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 09P IS TRACKING QUICKLY EAST-SOUTHEASTWARD WITHIN THE ENHANCED FLOW BETWEEN A DEEP TROUGH AND THE STR POSITIONED TO THE EAST. TC 09P WILL WEAKEN STEADILY THROUGHOUT THE FORECAST DUE TO INCREASING VERTICAL WIND SHEAR UNDER THE SUBTROPICAL WESTERLIES. THEREFORE, THE SYSTEM IS EXPECTED TO TRANSITION TO A SUBTROPICAL CYCLONE WITHIN THE NEXT 36 TO 48 HOURS AS IT ACCELERATES SOUTHEASTWARD.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN TIGHT AGREEMENT LENDING HIGH CONFIDENCE TO THE JTWC TRACK FORECAST. RELIABLE INTENSITY GUIDANCE ALSO SUPPORTS THE JTWC INTENSITY FORECAST WITH MEDIUM CONFIDENCE WITH GUIDANCE INDICATING A SHORT-TERM INCREASE FOLLOWED BY STEADY WEAKENING.

THE AREA OF CONVECTION (INVEST 92P) PREVIOUSLY LOCATED NEAR 18.1S 48.4E IS NOW LOCATED NEAR 16.6S 150.8E, APPROXIMATELY 50 NM EAST-SOUTHEAST OF WILLIS ISLAND. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A PARTIALLY EXPOSED, ELONGATED AND DEFINED LOW LEVEL CIRCULATION CENTER (LLCC) WITH DISORGANIZED FLARING CONVECTION SHEARED TO THE EAST. ANIMATED RADAR IMAGERY DEPICTS LOW LEVEL RAIN BANDS WRAPPING INTO A DEFINED CENTER JUST EAST OF WILLIS ISLAND. RECENT OBSERVATIONS FROM WILLIS ISLAND REPORT WINDS AT 25-30 KNOTS AND PRESSURE AS LOW AS 996MB WITH 999MB BEING THE AVERAGE. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS FOR DEVELOPMENT WITH MODERATE EQUATORWARD OUTFLOW AND WEAK POLEWARD OUTFLOW ALOFT, LOW (10-15KT) VWS, AND WARM (28-29C) SST. GLOBAL MODELS ARE IN AGREEMENT THAT 92P WILL DEVELOP GALE-FORCE WINDS ALONG THE SOUTHERN QUADRANT AS IT TRACKS EAST-SOUTHEASTWARD OVER THE NEXT 24-48 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 998 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO HIGH.

GLOBAL MODELS ARE IN AGREEMENT THAT 92P WILL DEVELOP GALE-FORCE WINDS ALONG THE SOUTHERN QUADRANT AS IT TRACKS EAST-SOUTHEASTWARD OVER THE NEXT 24-48 HOURS.