THE AREA OF CONVECTION (INVEST 90W) PREVIOUSLY LOCATED NEAR
5.7N 153.4E IS NOW LOCATED NEAR 6.4N 153.0E, APPROXIMATELY 89 NM
SOUTHEAST OF CHUUK. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICT
A BROAD AREA OF CYCLONIC TURNING WITH DENSE FLARING CONVECTION OBSCURING
THE LOW LEVEL CENTER. THE POSITION IS BASED ON THE CENTROID OF THE
OVERALL CIRCULATION AND PROMINENT MID-LEVEL FLOW. ENVIRONMENTAL ANALYSIS
INDICATES 90W IS CURRENTLY IN A FAVORABLE ENVIRONMENT FOR DEVELOPMENT
BEING CENTERED IN A LOWER POCKET (10-15 KT) OF VERTICAL WIND SHEAR, WARM
(29-30 C) SEA SURFACE TEMPERATURES, AND A POINT SOURCE JUST EAST OF THE
LOW-LEVEL CIRCULATION CENTER (LLCC) ASSISTING WITH MODERATE POLEWARD
OUTFLOW. GLOBAL MODELS ARE IN GOOD AGREEMENT ON A WESTWARD TRACK WITH
INTENSIFICATION OVER THE NEXT 24-48 HOURS. MAXIMUM SUSTAINED SURFACE
WINDS ARE ESTIMATED AT 13 TO 18 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 REMAINS MEDIUM.
WTPN21 PGTW 081800
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 90W)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
120 NM EITHER SIDE OF A LINE FROM 8.6N 153.4E TO 9.3N 149.7E
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 18 TO 23 KNOTS. METSAT
IMAGERY AT 081730Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 9.2N 152.4E. THE SYSTEM IS MOVING NORTHWESTWARD AT 06 KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 90W) PREVIOUSLY LOCATED NEAR
5.7N 153.4E IS NOW LOCATED NEAR 9.2N 152.4E, APPROXIMATELY 520 NM EAST-
SOUTHEAST OF GUAM. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS DEEP
CONVECTION OBSCURING THE BROAD LOW-LEVEL CIRCULATION CENTER (LLCC) WITH
CONVECTIVE BANDING WRAPPING ALONG THE SOUTHERN SEMICIRCLE. ENVIRONMENTAL
ANALYSIS REVEALS A FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH STRONG
EQUATORWARD OUTFLOW, LOW VERTICAL WIND SHEAR (10-15 KTS), AND WARM SEA
SURFACE TEMPERATURES (28-29 C). GLOBAL MODELS AGREE ON 90W SLOWLY
TRACKING GENERALLY WESTWARD AS IT CONSOLIDATES OVER THE NEXT 24-48
HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 18 TO 23 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1005 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
091800Z.//
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