WTPN22 PGTW 180030
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/171430Z AUG 25//
AMPN/REF IS TROPICAL CYCLONE FORMATION ALERT (WTPN21 PGTW 171430)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
080 NM EITHER SIDE OF A LINE FROM 19.2N 108.1E TO 21.7N 107.2E
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 180030Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 19.4N 108.0E. THE SYSTEM IS MOVING WEST-NORTHWESTWARD AT 16
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 91W) PREVIOUSLY LOCATED NEAR 
17.9N 111.1E IS NOW LOCATED NEAR 19.4N 108.0E, APPROXIMATELY 155 NM 
SOUTHEAST OF HANOI. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) 
DEPICTS DEEP CONVECTION BUILDING OVER A CONSOLIDATING LOW-LEVEL 
CIRCULATION CENTER (LLCC), ALSO HAVING CURVED CONVECTIVE BANDING TO THE 
SOUTHEAST. A CONTRACTING WIND FIELD AND REDUCTION OF THE RADIUS OF 
MAXIMUM WINDS INDICATES THAT A TRANSITION FROM A MONSOON DEPRESSION INTO 
A TROPICAL DEPRESSION IS COMMENCING. ENVIRONMENTAL ANALYSIS FOR THE AREA 
INDICATES FAVORABLE CONDITIONS FOR DEVELOPMENT WITH LOW VERTICAL WIND 
SHEAR (10-15 KTS), WARM SEA SURFACE TEMPERATURES (30-31 C), AND MODERATE 
EQUATORWARD OUTFLOW ALOFT. GLOBAL MODELS ARE IN GOOD AGREEMENT THAT 91W 
WILL TRACK NORTHWARD OVER THE NEXT 24-36 HOURS. ECENS AND GEFS ENSEMBLE 
GUIDANCE SHOW A FAIR AGREEMENT THAT 91W WILL DEVELOP, BUT WITH THE ECENS 
MODEL BEING MORE AGGRESSIVE THAN THE GEFS. MAXIMUM SUSTAINED SURFACE 
WINDS ARE ESTIMATED AT 23 TO 28 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 HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 
190030Z.
4. SEE REF A FOR DETAILS ON A TROPICAL CYCLONE FORMATION ALERT
LOCATED NEAR 21.5N 127.1E.//
NNNN