TC 08S(BATSIRAI): set to take on subtropical features// Invest 92P and Invest 93S: Tropical Cyclone Formation Alerts, 08/03UTC

JTWC IS ISSUING 12HOURLY WARNINGS ON TC 08S(BATSIRAI). 3HOURLY SATELLITE BULLETINS ARE ISSUED ON 08S, INVEST 92P AND INVEST 93S.

08/02UTC.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 08S IS FORECAST TO ACCELERATE SOUTHWARD ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE AND BEGIN TO WEAKEN AS VERTICAL WIND SHEAR INCREASES AND SEA SURFACE TEMPERATURES COOL TO BELOW 26C OVER THE NEXT 12 HOURS. AS THE SYSTEM MOVES FURTHER SOUTH AND NEARS THE SUBTROPICAL JET, IT WILL BEGIN TO TAKE ON MORE SUBTROPICAL CHARATERISTICS AND SHOULD COMPLETE SUBTROPICAL TRANSITION BY 24H AT THE INTENSITY OF 40 KTS.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN EXPOSED, BROAD LOW-LEVEL CIRCULATION WITH CONVECTION SHEARED TO THE SOUTH AND SOUTHEAST. THE INITIAL POSITION IS BASED ON AN EXPOSED LOW-LEVEL BANDING IN A 072244Z AMSR2 89GHZ IMAGE AND THE INITIAL INTENSITY IS BASED ON EXTRAPOLATION FROM A 071932Z ASCAT-B IMAGE SHOWING 45-50 KT WINDS IN THE SOUTHWEST QUADRANT. THE SYSTEM IS STRUGGLING TO REINTENSIFY DUE TO SIGNIFICANT DRY AIR ENTRAINMENT FROM THE WEST AND INCREASING VERTICAL WIND SHEAR.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH ONLY A 95KM CROSS-TRACK SPREAD AT 48H. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT, WITH ALL MODELS INDICATING A STEADY WEAKENING TREND FOR THE REMAINDER OF THE FORECAST.

1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 150 KM EITHER SIDE OF A LINE FROM 18.9S 166.9E TO 20.5S 168.3E WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME. WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. METSAT IMAGERY AT 080230Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 18.9S 167.0E. THE SYSTEM IS MOVING EAST-NORTHEASTWARD AT 15 KM/H. 2. REMARKS: THE AREA OF CONVECTION (INVEST 92P) PREVIOUSLY LOCATED NEAR 19.7S 165.9E IS NOW LOCATED NEAR 19.4S 166.3E, APPROXIMATELY 280 KM SOUTHWEST OF PORT VILA, VANUATU. ANIMATED MULTISPECTRAL IMAGERY AND A 071428Z AMSR2 89GHZ IMAGE DEPICT FORMATIVE BANDING WRAPPING INTO A LOW LEVEL CIRCULATION (LLC). IN ADDITION, THERE ARE DEEP, FRAGMENTED POCKETS OF CONVECTION TO THE NORTHERN AND WESTERN PERIPHERIES OF THE LLC. ENVIRONMENTAL ANALYSIS INDICATES FAVORABLE CONDITIONS FOR DEVELOPMENT TO INCLUDE ROBUST POLEWARD OUTFLOW, MODERATE (15-20KT) VERTICAL WIND SHEAR, AND WARM (28-29C) SEA SURFACE TEMPERATURES. GLOBAL MODELS TO INCLUDE GFS, NAVGEM, AND JMA ARE IN AGREEMENT THAT THE INVEST 92P GRADUALLY INTENSIFIES OVER THE NEXT 48 HOURS AND TRACKS EAST TOWARD FIJI. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25 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 HIGH.

GLOBAL MODELS TO INCLUDE GFS, NAVGEM, AND JMA ARE IN AGREEMENT THAT THE INVEST 92P GRADUALLY INTENSIFIES OVER THE NEXT 48 HOURS AND TRACKS EAST TOWARD FIJI.

1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 185 KM EITHER SIDE OF A LINE FROM 14.7S 105.6E TO 19.1S 105.8E WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME. WINDS IN THE AREA ARE ESTIMATED TO BE 25 TO 30 KNOTS. METSAT IMAGERY AT 080230Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 15.0S 105.6E. THE SYSTEM IS MOVING SOUTHWARD AT 22 KM/H. 2. REMARKS: THE AREA OF CONVECTION (INVEST 93S) PREVIOUSLY LOCATED NEAR 11.5S 105.4E IS NOW LOCATED NEAR 13.8S 105.5E, APPROXIMATELY 375 KM SOUTH OF CHRISTMAS ISLAND. ANIMATED MULTISPECTRAL IMAGERY AND A 072335Z SSMIS 91GHZ IMAGE DEPICT A LOW LEVEL CIRCULATION (LLCC) WITH DEEP BANDING WRAPPING INTO THE LLCC. IN ADDITION, THERE IS BROAD, DEEP CONVECTION WITHIN THE CENTRAL AND NORTHERN PERIPHERIES OF THE SYSTEM. ENVIRONMENTAL ANALYSIS INDICATES FAVORABLE CONDITIONS FOR DEVELOPMENT TO INCLUDE FAIR POLEWARD OUTFLOW, LOW (10-15KT) VERTICAL WIND SHEAR, AND VERY WARM (29-30) SEA SURFACE TEMPERATURES. GLOBAL MODELS ARE IN AGREEMENT THAT THE INVEST 93S IS A COMPACT SYSTEM THAT WILL TRACK WEST-SOUTHWEST SLOWLY INTENSIFYING 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 1002 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH.

GLOBAL MODELS ARE IN AGREEMENT THAT THE INVEST 93S IS A COMPACT SYSTEM THAT WILL TRACK WEST-SOUTHWEST SLOWLY INTENSIFYING OVER THE NEXT 24-48 HOURS.

MAP: CIMSS.