WTIO21 PGTW 310600
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 91B)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
120 NM EITHER SIDE OF A LINE FROM 9.6N 91.3E TO 13.7N 83.8E
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 28 TO 33 KNOTS. METSAT
IMAGERY AT 310600Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 9.7N 90.9E. THE SYSTEM IS MOVING WEST-NORTHWESTWARD AT 14
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 91B) PREVIOUSLY LOCATED NEAR 
9.5N 93.2E IS NOW LOCATED NEAR 9.7N 90.9E, APPROXIMATELY 159 NM 
SOUTHWEST OF PORT BLAIR. ANIMATED MULTISPECTRAL SATELLITE IMAGE (MSI) 
AND A 302239Z SSMIS F18 91GHZ MICROWAVE IMAGE DEPICT A RAPIDLY 
CONSOLIDATING LLCC WITH DEEP, PERSISTENT CONVECTION BUILDING OVER THE 
CENTER OF THE LLCC. THE IMAGERY ALSO DEPICTS CURVED DEEP CONVECTIVE 
BANDING AND FORMATIVE RAIN BANDS FROM THE SOUTHERN QUADRANT TO THE 
NORTHERN QUADRANT. A PARTIAL 310331Z ASCAT-B PASS REVEALED AN EXTENSIVE 
FIELD OF 25-30KT WINDS ACROSS THE NORTHERN THROUGH SOUTHWESTERN SECTORS, 
WHILE A SMALL REGION OF 30-35KT WINDS WERE PRESENT IN THE SOUTHWESTERN 
QUADRANT OF THE LLCC. ENVIRONMENTAL ANALYSIS REVEALS A FAVORABLE 
ENVIRONMENT FOR DEVELOPMENT WITH LOW TO MODERATE EASTERLY VERTICAL WIND 
SHEAR (VWS) OF 10-20KTS, GOOD UPPER-LEVEL WESTWARD AND POLEWARD OUTFLOW, 
AND WARM SEA SURFACE TEMPERATURES (SST) OF 29-30C. GLOBAL DETERMINISTIC 
AND ENSEMBLE MODELS ARE IN WEAK AGREEMENT ON THE FUTURE EVOLUTION OF 
91B. THE GFS AND GEFS ENSEMBLES ARE PORTRAYING WEAK DEVELOPMENT, WHILE 
AND ECMWF AND ECEPS ARE PORTRAYING A MORE AGGRESSIVE DEVELOPMENT 
TIMELINE. THE OPERATIONAL GOOGLE DEEPMIND (GDM) ENSEMBLE IS ALSO 
AGGRESSIVE IN DEVELOPING 91B, INDICATING A 98 PERCENT PROBABILITY OF A 
TC WITHIN 12-18 HOURS. ALL MODELS ARE IN AGREEMENT IN 91B TRACKING 
NORTHWEST TOWARD MAINLAND INDIA OVER THE NEXT 24HRS. MAXIMUM SUSTAINED 
SURFACE WINDS ARE ESTIMATED AT 28 TO 33 KNOTS. MINIMUM SEA LEVEL 
PRESSURE IS ESTIMATED TO BE NEAR 1009 MB. THE POTENTIAL FOR THE 
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS 
IS HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 
010600Z.//
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