WDPN33 PGTW 120300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (EIGHTEEN) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 18W (EIGHTEEN), LOCATED APPROXIMATELY 
287 
NM NORTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 10 
KNOTS 
(KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY (MSI) REVEALS FLARING DEEP CONVECTION OVERHEAD A DEFINED LOW-
LEVEL CIRCULATION CENTER (LLCC) WITH CONVECTIVE BANDING WRAPPING 
INTO 
IT. AN 112300Z GMI 89 GHZ MICROWAVE IMAGE LENDS HIGH CONFIDENCE TO 
THE INITIAL POSITION AS IT DEPICTS THE CONVECTIVE BANDS WRAPPING 
INTO 
THE LLCC. A 120029Z ASCAT-B IMAGE DEPICTS A SWATH OF 25-30 KT WINDS 
IN THE NORTHEAST QUADRANT WITH WEAKER WINDS TO THE SOUTH. THE 
INITIAL 
INTENSITY IS SET AT 30 KTS, HEDGED HIGHER THAN MULTI-AGENCY DVORAK 
CURRENT INTENSITY ESTIMATES OF T1.5 (25 KTS) BY PGTW, RJTD, AND KNES 
BASED ON THE AFOREMENTIONED ASCAT DATA. SUPPORTED BY LOW (<10 KTS) 
VERTICAL WIND SHEAR (VWS), ESTABLISHED EQUATORWARD OUTFLOW, AND WARM 
(29-30 CELSIUS) SEA SURFACE TEMPERATURES (SST), TD 18W IS MOVING 
THROUGH A HIGHLY FAVORABLE ENVIRONMENT FOR DEVELOPMENT. A DEEP-
LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH IS ACTING AS THE 
PRIMARY 
STEERING MECHANISM AS TD 18W TRACKS ALONG ITS SOUTHERN PERIPHERY. 
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. THE AFOREMENTIONED STR WILL ACT AS THE STEERING MECHANISM 
THROUGHOUT THE ENTIRE FORECAST PERIOD. THROUGH TAU 36, TD 18W IS 
FORECAST TO TRACK GENERALLY WESTWARD AS IT STEADILY STRENGTHENS TO A 
PEAK INTENSITY OF 60 KTS BY TAU 36 DUE TO CONTINUED FAVORABLE 
ENVIRONMENTAL CONDITIONS. AFTERWARDS, THE SYSTEM WILL SHIFT TO A 
WEST-NORTHWESTWARD TRACK THROUGH TAU 72, GRADUALLY WEAKENING AS IT 
TRACKS OVER HAINAN AND INTO THE GULF OF TONKIN. PRIOR TO TAU 72, TD 
18W IS EXPECTED TO MAKE LANDFALL SOUTH OF HANOI, VIETNAM. NUMERICAL 
MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 36 WITH A SPREAD OF 
ONLY 46 NM. HOWEVER, THIS SPREAD INCREASES TO 180 NM BY TAU 72, 
PLACING SOME UNCERTAINTY IN THE EXACT LANDFALL LOCATION.
   C. IN THE EXTENDED RANGE, TD 18W WILL TURN WEST-SOUTHWESTWARD 
AFTER LANDFALL AND RAPIDLY WEAKEN AS IT TRANSITS OVER THE RUGGED 
TERRAIN OF NORTHERN VIETNAM. THE SYSTEM IS FORECAST TO DISSIPATE 
OVER 
LAND BY TAU 96. THE JTWC FORECAST TRACK LIES NEAR THE MULTI-MODEL 
CONSENSUS; HOWEVER, DUE TO THE INCREASING MODEL SPREAD IN THE 
EXTENDED RANGE, THERE IS OVERALL FAIR CONFIDENCE IN THE JTWC 
FORECAST 
TRACK.//
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