WDPN31 PGTW 142100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 04W (FOUR) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.6N 117.9E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 254 NM NORTHWEST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A LARGE
TROPICAL CYCLONE (400+NM ACROSS) THAT CONSOLIDATED FROM A MONSOON
DEPRESSION WITH BROAD RAIN BANDS TRAILING SOUTHWESTWARD ALL THE
WAY TO CELEBES SEA. THE INITIAL POSITION AND INTENSITY ARE ASSESSED
WITH HIGH CONFIDENCE FROM THE 141351Z ASCAT BULLSEYE PASS. THE
INTENSITY IS ALSO SUPPORTED BY THE PGTW AND D-PRINT DVORAK
ESTIMATES AND REFLECTS THE 6-HR CONVECTIVE AND WRAP IMPROVEMENTS.
ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH STRONG POLEWARD
OUTFLOW, LOW VWS ALOFT, AND WARM SST IN THE SOUTH CHINA SEA (SCS).
A TUTT TO THE NORTHWEST, ALSO EVIDENT IN THE EIR LOOP, HAS BEGUN TO
ENHANCE POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER,
EAST-WEST ORIENTED SUBTROPICAL RIDGE.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 25 KTS AT 141730Z
   CIMSS D-PRINT: 31KTS AT 141800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TD 04W WILL CONTINUE GENERALLY
WEST-NORTHWESTWARD UNDER THE STEERING STR, TRACK OVER THE WARM SCS, 
MAKE LANDFALL ON THE LEIZHOU PENINSULA NEAR ZHANJIANG AROUND TAU 72, 
THEN ACROSS THE GULF OF TONKIN BEFORE MAKING A FINAL LANDFALL ALONG 
THE VIETNAM-CHINA BORDER AROUND TAU 84. THE FAVORABLE ENVIRONMENT 
WILL FUEL SIGNIFICANT INTENSIFICATION TO 80KTS BY TAU 48 (PEAK 
INTENSITY TO APPROXIMATELY 90KTS WILL OCCUR AROUND TAU 60). LAND 
INTERACTION WITH RUGGED TERRAIN WILL MOSTLY BE RESPONSIBLE FOR THE 
GRADUAL, THEN RAPID WEAKENING AFTER TAU 72, REDUCING 04W TO 25KTS BY 
TAU 120 AS IT TRACKS ALONG THE NORTHERN BOUNDARY OF VIETNAM.   

MODEL DISCUSSION: THERE IS OVERALL GOOD AGREEMENT WITH THE MAIN
PACK OF NUMERICAL TRACK MODELS WITH AN EVEN AND GRADUAL SPREAD TO
138NM BY TAU 72. AFTERWARD, THE TRACKERS SIGNIFICANTLY SPREAD OUT
TO 630NM+ BY TAU 120. NAVGEM IS THE SOLE OUTLIER WITH A FORECAST
TRACK THAT DEVIATES 60 DEGREES NNW-WARD FROM THE MAIN PACK. IN VIEW
OF THESE, THERE IS MEDIUM CONFIDENCE IN THE JTWC TRACK AND
INTENSITY FORECASTS UP TO TAU 72, THEN LOW CONFIDENCE AFTERWARD. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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