Tropical Storm VICENTE Advisory Sat Jul 21

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 09W (NINE)
WARNING NR 02//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 09W (NINE), LOCATED APPROXIMATELY 285 NM
NORTH-NORTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 14
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS AN ELONGATED LOW-LEVEL CIRCULATION CENTER (LLCC)
WITH MULTIPLE MESO-VORTICE LOCATED IN THE EAST AND NORTHEAST
SECTORS. THE CURRENT POSITION IS BASED ON RECENT SURFACE
OBSERVATIONS FROM LAOAG AIRPORT INDICATING SOUTHERLY WINDS, AND
SOUTHWESTERLIES REPORTED FROM MANILA. THESE REPORTS SUGGEST THE
LLCC IS NORTHWEST OF THE NORTHERN PHILIPPINES. A 210004Z SSMIS 37
GHZ IMAGE DEPICTS THE BROAD LLCC AND WAS ALSO USED FOR THE CURRENT
POSITION, WHICH LIES BETWEEN THE PGTW AND RJTD CENTER FIXES. DUE TO
THE CONTINUED CYCLING OF MESO-VORTICE AND ELONGATED NATURE OF THE
LLCC, THERE REMAINS LOW CONFIDENCE IN THE CURRENT POSITION. THE
CURRENT INTENSITY CONTINUES TO BE BASED ON SURFACE MSLP
OBSERVATIONS OF 1000 MB AND DVORAK ESTIMATES OF 25 KNOTS FROM PGTW,
RJTD, AND KNES. UPPER-LEVEL ANALYSIS INDICATES THAT THE PREVIOUS
TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL THAT WAS LOCATED
EAST OF THE LLCC HAS NOW FILLED AND OPENED INTO A TROUGH-RIDGE-
TROUGH PATTERN. TD 09W IS APPROXIMATELY 10 DEGREES SOUTH OF AN EAST-
WEST ORIENTATED SUBTROPICAL RIDGE (STR) AXIS UNDER MODERATE (15-20
KNOTS) EASTERLY VERTICAL WIND SHEAR WITH GOOD DIVERGENCE ALOFT TO
THE WEST WHERE EQUATORWARD OUTFLOW IS AMPLE.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TD 09W WILL CONTINUE TO TRACK WESTWARDS UNDER THE SOUTHERN
PERIPHERY OF A BUILDING, ZONAL ORIENTATED, STR DURING THE ENTIRE
FORECAST PERIOD. GRADUAL CONSOLIDATION, AND INTENSIFICATION, SHOULD
OCCUR DURING THE NEXT SEVERAL DAYS AS UPPER-LEVEL CONDITIONS BECOME
MORE FAVORABLE AND ALONG TRACK SEA SURFACE TEMPERATURES RANGE FROM
28-30C. SOME ADJUSTMENT TO THE SHORT-TERM POSITION AND TRACK MAY BE
NEEDED AS THE LLCC CONTINUES TO COALESCE.
   C. IN THE EXTENDED FORECAST, TD 09W SHOULD BE ABLE TO MAINTAIN
STRONG TD STRENGTH AS IT TRACKS OVER THE NORTHERN WATERS OF THE
GULF OF TONKIN. BY TAU 120, THE SYSTEM SHOULD BE DISSIPATING
OVERLAND NEAR NORTHERN VIETNAM. NUMERICAL MODEL GUIDANCE CONTINUES
TO REMAIN TIGHTLY CLUSTERED DURING THE FIRST THREE DAYS.
THEREAFTER, THE GUIDANCE BEGINS TO SLIGHTLY DIVERGE WITH THE GFS
RIGHT-MOST OF THE CONSENSUS AND THE GFDN SWITCHING TO THE LEFT-MOST
OUTLIER. DUE TO THE TIGHT GUIDANCE ENVELOPE THERE IS HIGH
CONFIDENCE IN THE OFFICIAL JTWC TRACK FORECAST. HOWEVER, SINCE THE
CURRENT POSITION CONFIDENCE IS LOW A SLIGHT ADJUSTMENT IN THE SHORT-
TERM MAY BE NEEDED IN SUBSEQUENT FORECASTS, BUT THE OVERALL
WESTWARDS FORECAST TRACK IS WELL SUPPORTED BY THE SYNOPTIC
ENVIRONMENT AND MODEL DEPICTION.//
NNNN
NNNN