WDPN31 PGTW 210300
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.//
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