(1) AN AREA OF CONVECTION (INVEST 99W) HAS PERSISTED NEAR 6.3N
127.8E, APPROXIMATELY 140 NM EAST-SOUTHEAST OF DAVAO, PHILIPPINES.
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS AN EXTENSIVE
REGION OF PERSISTENT DEEP CONVECTION SHEARED TO THE NORTH AND WEST
OF A BROAD LOW-LEVEL CIRCULATION (LLC). A 171654Z AMSR2 91GHZ
COMPOSITE MICROWAVE IMAGE REVEALS A PARTIALLY-EXPOSED LLC WITH
CURVED BANDING OVER THE WESTERN SEMICIRCLE. A 171207Z ASCAT-A IMAGE
SHOWS AN ELONGATED CIRCULATION WITH 20-25 KNOT WINDS OVER THE
NORTHERN AND WESTERN SEMICIRCLES WITH 15-20 KNOT WINDS ELSEWHERE.
UPPER-LEVEL ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH MODERATE
TO STRONG EASTERLY VERTICAL WIND SHEAR OFFSET BY STRONG DIFFLUENCE.
GLOBAL MODELS INDICATE A WEST-NORTHWESTWARD TRACK OVER MINDANAO
WHICH WILL HINDER DEVELOPMENT FOR THE NEXT 36 HOURS, HOWEVER, THE
SYSTEM MAY INTENSIFY AFTER TAU 36 AS IT TRACKS OVER THE SULU SEA AND
INTERACTS WITH NORTHEAST SURGE FLOW. MAXIMUM SUSTAINED SURFACE WINDS
ARE ESTIMATED AT 15 TO 20 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 MEDIUM.
WTPN21 PGTW 182030
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 99W)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
200 NM EITHER SIDE OF A LINE FROM 8.5N 123.7E TO 10.4N 116.0E
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 20 TO 25 KNOTS. METSAT
IMAGERY AT 182000Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 8.7N 123.2E. THE SYSTEM IS MOVING WEST-NORTHWESTWARD AT 12
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 99W) PREVIOUSLY LOCATED
NEAR 6.8N 126.3E IS NOW LOCATED NEAR 8.7N 123.2E, APPROXIMATELY
311NM EAST-SOUTHEAST OF PUERTO PRINCESA, PHILIPPINES. ANIMATED
ENHANCED INFRARED SATELLITE IMAGERY AND AN 181736Z AMSR2 GW1 89GHZ
MICROWAVE IMAGE DEPICT A SLOWLY CONSOLIDATING LOW LEVEL CIRCULATION
(LLC) WITH FLARING CONVECTION SHEARED TO THE NORTHWEST QUADRANT.
UPPER LEVEL ANALYSIS REVEALS THAT 99W IS IN A MARGINALLY FAVORABLE
ENVIRONMENT FOR DEVELOPMENT WITH WARM SST (28-29C), MODERATE
VERTICAL WIND SHEAR (10-20 KNOTS), AND STRONG POLEWARD OUTFLOW.
GLOBAL MODELS INDICATE THE SYSTEM WILL INTENSIFY AS IT BEGINS TO TAP
INTO A NORTHEAST SURGE EVENT AS THE SYSTEM CONTINUES TO TRACK WEST-
NORTHWESTWARD. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20
TO 25 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1004
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
192030Z.
//
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