WTPN21 PGTW 170530
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 12.7N 158.9E TO 14.7N 152.4E
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 15 TO 20 KNOTS. METSAT IMAGERY AT
170500Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 12.6N
158.3E. THE SYSTEM IS MOVING WESTWARD AT 05 KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 91W) PREVIOUSLY LOCATED
NEAR 13.2N 162.0E IS NOW LOCATED NEAR 12.6N 158.3E, APPROXIMATELY
795NM EAST OF GUAM. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS
LOW-LEVEL CLOUD LINES WRAPPING INTO AN EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH ISOLATED DEEP CONVECTION FLARING OVER THE
SOUTHWEST QUADRANT OF THE LLCC. A 170240Z GMI 36GHZ IMAGE SHOWS
FRAGMENTED BANDING OVER THE WESTERN SEMICIRCLE AND SHALLOW BANDING
OVER THE EASTERN SEMICIRCLE WRAPPING INTO A RAGGED LLCC. UPPER-LEVEL
ANALYSIS INDICATES A MARGINALLY-FAVORABLE ENVIRONMENT WITH LOW TO
MODERATE NORTHERLY VERTICAL WIND SHEAR OFFSET BY POLEWARD OUTFLOW
INTO A TUTT CELL POSITIONED TO THE NORTHEAST. SST VALUES ARE
CONDUCIVE FOR FURTHER DEVELOPMENT AT 29C. NUMERICAL MODELS INDICATE
A WESTWARD TO NORTHWESTWARD TRACK OVER THE NEXT TWO DAYS WITH
GRADUAL INTENSIFICATION AS THE SYSTEM MOVES TOWARD THE NORTHERN
MARIANAS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15 TO 20
KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1006 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
180530Z.//
NNNN
(1) THE AREA OF CONVECTION (INVEST 91W) PREVIOUSLY LOCATED
NEAR 12.7N 167.2E, IS NOW LOCATED NEAR 13.4N 163.0E, APPROXIMATELY
750 NM EAST-NORTHEAST OF CHUUK. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS DEEP CONVECTION BUILDING OVER A SLOWLY CONSOLIDATING
LOW LEVEL CIRCULATION CENTER. A 151506Z AMSR2 GW1 89GHZ MICROWAVE
IMAGE DEPICTS FRAGMENTED BANDING BEGINNING TO FORM AROUND THE
SLIGHTLY ELONGATED LOW LEVEL CIRCULATION. THE DISTURBANCE IS LOCATED
IN AN AREA OF EXCELLENT UPPER LEVEL OUTFLOW, LOW (10-15 KT) VERTICAL
WIND SHEAR, AND VERY WARM SEA SURFACE TEMPERATURES (28-30 C). GLOBAL
MODELS ARE IN GOOD AGREEMENT THAT THE SYSTEM WILL GRADUALLY DEVELOP
AS IT TRACKS WESTWARD OVER THE NEXT FEW DAYS. MAXIMUM SUSTAINED
SURFACE WINDS ARE ESTIMATED AT 15 TO 20 KNOTS. MINIMUM SEA LEVEL
PRESSURE IS ESTIMATED TO BE NEAR 1003 MB. THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS IS UPGRADED TO MEDIUM.
