WTXS21 PGTW 181800
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
160 NM EITHER SIDE OF A LINE FROM 12.8S 96.8E TO 15.7S 95.0E
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 181200Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 13.1S 96.6E. THE SYSTEM IS MOVING WESTWARD AT 12 KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 91S) PREVIOUSLY LOCATED NEAR
12.8S 98.1E IS NOW LOCATED NEAR 13.1S 96.6E, APPROXIMATELY 57.2 NM
SOUTH-SOUTHWEST OF COCOS ISLANDS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY FROM HIMAWARI-9 DEPICTS CURVED DEEP CONVECTIVE
BANDING OVER A CONSOLIDATING LLCC. A 1532Z AMSU-B MICROWAVE IMAGE SHOWS
THAT THE VORTEX REMAINS SLIGHTLY TILTED WESTWARD WITH HEIGHT, BUT
CONVECTIVE ORGANIZATION HAS IMPROVED IN THE WESTERN SEMICIRCLE OVER THE
PAST SIX HOURS.  A 181730Z SURFACE OBSERVATION FROM COCOS ISLAND
INTERNATIONAL AIRPORT SHOWS NORTHWESTERLY 26 KNOT WINDS WITH GUSTS OF
37 KNOTS AND AN MSLP VALUE OF 1004MB. ENVIRONMENTAL ANALYSIS INDICATES
THAT INVEST 91S IS IN A FAVORABLE ENVIRONMENT FOR FURTHER DEVELOPMENT
DUE TO WARM (29-30C) SEA SURFACE TEMPERATURES, MODERATE (15–20 KNOTS)
VERTICAL WIND SHEAR, AND STRONG POLEWARD OUTFLOW ALOFT. GLOBAL MODELS
ARE IN AGREEMENT THAT 91S WILL STEADILY DEVELOP AND TRANSIT TO THE
SOUTHWEST DURING THE NEXT 24 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE
ESTIMATED AT 28 TO 33 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO
BE NEAR 998 MB.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 191800Z.
//
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