(2) AN AREA OF CONVECTION (INVEST 91W) HAS PERSISTED NEAR
17.9N 126.0E, APPROXIMATELY 306 NM NORTHEAST OF MANILA. A 300645Z
85GHZ SSMI IMAGE DEPICTS LOW LEVEL BANDING WITH SCATTERED
CONVECTION. UPPER LEVEL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT
WITH GOOD EQUATORWARD OUTFLOW AND LOW (<15 KNOTS) VERTICAL WIND
SHEAR. SSTS ARE FAVORABLE AT 29-30 DEGREES CELSIUS. GLOBAL MODELS
SHOW 91W TRACKING WESTWARD WITH STEADY INTENSIFICATION OVER THE NEXT
24 TO 48 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15
TO 20 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 LOW.
(2) THE AREA OF CONVECTION (INVEST 91W) PREVIOUSLY LOCATED
NEAR 17.9N 126.0E, IS NOW LOCATED NEAR 18.9N 122.9E, APPROXIMATELY
78 NM EAST-NORTHEAST OF APARRI, PHILIPPINES. AMSI SHOWS A
CONSOLIDATING LOW LEVEL CIRCULATION CENTER WITH FORMATIVE BANDING
WRAPPING FROM THE WEST. A 310107Z MHS METOP-A 89GHZ MICROWAVE IMAGE
REVEALS THE AREA LARGELY DEVOID OF ANY DEEP CONVECTION. A 310150Z
ASCAT-C PARTIAL ASCAT PASS SHOWS 20 TO 25 KNOT WINDS ON THE NORTH
SIDE OF THE LLC. 91W IS CURRENTLY IN A MARGINAL ENVIRONMENT WITH
MODERATE EQUATORWARD OUTFLOW AND WARM (29 TO 30 CELSIUS) SSTS BEING
OFFSET BY HIGH (20 TO 25 KNOT) VWS. GLOBAL MODELS ARE IN GOOD
AGREEMENT THAT 91W WILL TRACK WESTWARD INTO THE SOUTH CHINA SEA AND
INTENSIFY. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15 TO 20
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 UPGRADED TO MEDIUM.
WTPN21 PGTW 311900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 91W)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
160 NM EITHER SIDE OF A LINE FROM 18.8N 119.0E TO 18.2N 109.4E
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 20 TO 25 KNOTS. METSAT
IMAGERY AT 311800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 18.8N 118.3E. THE SYSTEM IS MOVING WEST-SOUTHWESTWARD AT 13
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 91W) LOCATED NEAR 18.8N
118.3E, APPROXIMATELY 295 NM NORTH-NORTHWEST OF MANILA, THE
PHILIPPINES. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A
311332Z 89GHZ MHS MICROWAVE IMAGE DEPICT A PARTIALLY EXPOSED LOW
LEVEL CIRCULATION CENTER (LLCC) WITH FLARING CONVECTION ALONG THE
SOUTHWESTERN ARC OF THE SYSTEM. A 311334Z PARTIAL ASCAT PASS SHOWS A
BROAD REGION OF 20-25 KNOT WINDS THROUGH THE STRAIT OF LUZON, TAKING
ON SOME CURVATURE NEAR THE LLCC. THE ENVIRONMENT IS OVERALL
FAVORABLE FOR DEVELOPMENT, WITH WARM (30-32C) SEA SURFACE
TEMPERATURES, LOW (5-15 KNOT) VERTICAL WIND SHEAR AND EQUATORWARD
OUTFLOW OVER THE LLCC. UPPER LEVEL CONVERGENCE AND HIGH SHEAR ARE
CURRENTLY LIMITING CONVECTION OVER THE EASTERN PORTION OF THE
DISTURBANCE. GLOBAL MODELS ARE IN GOOD AGREEMENT THAT 91W WILL
CONTINUE TO DEVELOP AS IT TRACKS WEST OVER THE NEXT 24 HOURS.
HOWEVER, THE DISTURBANCE WILL REMAIN BROAD AND CONTINUE TO EXHIBIT
CHARACTERISTICS OF A MONSOON DEPRESSION. 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
011900Z.//
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