TC 08S(BATSIRAI): challenging forecast intensity-wise// Invest 91W down-graded to LOW//Invest 97P, 28/03utc

JTWC IS ISSUING 12HOURLY WARNINGS ON TC 08S(BATSIRAI) AND 3HOURLY SATELLITE BULLETINS ON 08S AND INVEST 91W.

28/02UTC.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE FIRST 24 HOURS OF THE FORECAST INTENSITY WAS LOWERED TO ACCOUNT FOR THE RAPID WEAKENING THAT OCCURRED. FORECAST DISCUSSION: TC BATSIRAI IS EXPECTED TO TRACK GENERALLY SOUTH-SOUTHWESTERLY TO WESTERLY OVER THE NEXT 48 HOURS WITHIN THE BROADER MONSOONAL GYRE FLOW, WHICH IS MODULATED BY THE STRONG DEEP- LAYER SUBTROPICAL RIDGE TO THE SOUTH. MID-LEVEL DRYING AND PERSISTENT SHEAR IS FORECAST TO HAMPER REDEVELOPMENT DURING THIS PERIOD. HOWEVER, AFTER 48H THE TRACK IS EXPECTED TO DEFLECT EQUATORWARD, ACCOMPANIED BY INCREASED MOISTENING AND A RELAXATION OF THE SHEAR. A WEAKNESS IN THE RIDGE SHOULD THEN ALLOW ANOTHER TURN TO THE SOUTH-SOUTHWEST AT THE END OF THE FORECAST. THE SMALL SIZE OF THE CURRENT CORE, COMBINED WITH THE BROADER INTERACTION WITH THE GYRE FLOW AND THE POOR GUIDANCE RELIABILITY THUS FAR MAKE THE INTENSITY FORECAST CHALLENGING. THE FORECAST IS SLIGHTLY HIGHER THAN THE CURRENT GUIDANCE ENVELOP GIVEN THE POTENTIAL TO RAPIDLY ADJUST TO ANY POSITIVE ENVIRONMENTAL CHANGES, ALTHOUGH THE FORECAST CALLS FOR THE SHEAR AND DRY ENVIRONMENT TO LIMIT INTENSIFICATION THROUGH 48H. A SECONDARY PEAK OF 70 KNOTS/CAT 1 IS ANTICIPATED AROUND 96H AS CONDITIONS IMPROVE. FORECAST CONFIDENCE IS GENERALLY LOW GIVEN THE LARGE SPREAD IN MODEL GUIDANCE AND INTENSITY CHALLENGES DESCRIBED BELOW.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS RAGGED DEEP CONVECTION OVER A COMPACT LOW LEVEL CIRCULATION CENTER, REFLECTING THE RAPID WEAKENING THAT HAS OCCURRED OVER THE PAST TWELVE HOURS FOLLOWING A VERY SHORT-LIVED PERIOD OF EXPLOSIVE DEEPENING. A 012723Z SSMIS PASS REVEALS DEEP CONVECTION IS DISPLACED TO THE SOUTHERN SEMI-CIRCLE DUE TO NORTHERLY VERTICAL WIND SHEAR. THE INITIAL POSITION WAS PLACED WITH GOOD CONFIDENCE BASED ON FIXES FROM PGTW AND FMEE, AND SUPPORTED BY THE SSMIS. THE INTENSITY WAS LOWERED TO 50 KNOTS, WITH BOTH AGENCIES HAVING A FINAL T-NUMBER OF 3.0, AND WITH CIS RANGING FROM 4.0 TO 5.0. THE LATEST CIMSS SATCON INDICATES 46 KNOTS, ALTHOUGH ADT HAS BEEN LOW-BIASED THROUGHOUT THE LAST DAY. SOME CONSIDERATION IS GIVEN TO THE SMALL SIZE OF THE SYSTEM. BATSORAI IS UNDER MODERATE 15 TO 20 KNOT SHEAR IN THE GFS, WHICH IS CONSISTENT WITH THE SSMIS IMAGERY. SST ANALYSIS INDICATES TC 08S IS TRACKING OVER A TONGUE OF SLIGHTLY COOLER (28 DEGREE CELSIUS) WATERS.

MODEL DISCUSSION: MODEL GUIDANCE IS IN FAIRLY GOOD AGREEMENT THROUGH 48H, AND THEN DIVERGES SIGNIFICANTLY. NAVGEM AND UKMET MODELS TAKE TC 08S ON A SOUTHWESTERLY TRACK, INTO THE RIDGE TO THE SOUTH. GFS AND GFS ENSEMBLE ARE NEAR THE TOP OF THE OTHER GROUPING WITH A WESTERLY TRACK, AND ARE ALSO THE FASTEST AIDS. THE ECMWF DETERMINISTIC IS CLOSER TO THE GFS, ALBEIT SLOWER, WHILE THE EC ENSEMBLE HAS A FAIR NUMBER OF MEMBERS THAT SUGGEST A MORE SOUTHWESTERLY TRACK IS POSSIBLE BEYOND 48H. THE FORECAST WAS PLACED BETWEEN THE GFS AND ECMWF DETERMINISTIC SOLUTIONS. INTENSITY GUIDANCE IS MIXED THROUGH 48H, BUT GENERALLY AGREES WITH THE EXPECTED RE-INTENSIFICATION AFTER 48H.

THE AREA OF CONVECTION (INVEST 91W) PREVIOUSLY LOCATED NEAR 9.4N 115.4E IS NOW LOCATED NEAR 11.5N 114.4E, APPROXIMATELY 520 KM WEST-NORTHWEST OF PUERTO PRINCESA, PHILIPPINES. ANIMATED MULTISPECTRAL SATELLITE IMAGERY AND A 272027Z SSMIS 91GHZ MICROWAVE IMAGE DISPLAY SHEARED CONVECTION DISPLACED TO THE NORTHEAST OF A DIMINISHING LOW LEVEL CIRCULATION. UPPER-LEVEL CONDITIONS ARE MARGINALLY-FAVORABLE WITH MODERATE (20 KNOTS) VERTICAL WIND SHEAR, FAIR POLEWARD OUTFLOW AND WARM (28-30C) SEA SURFACE TEMPERATURES. GLOBAL MODELS INDICATE NO SIGNIFICANT DEVELOPMENT AS THE SYSTEM TRACKS SLOWLY POLEWARD. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 10 TO 15 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1008 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS DOWNGRADED TO LOW.

GLOBAL MODELS INDICATE NO SIGNIFICANT DEVELOPMENT AS THE SYSTEM TRACKS SLOWLY POLEWARD.