WDPN31 PGTW 150300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (FOUR) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.1N 117.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 297 NM SOUTH-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A LARGE
SYSTEM (440NM+ ACROSS) IN THE SOUTH CHINA SEA (SCS) THAT CONTINUED
TO CONSOLIDATE AND HAS INTENSIFIED INTO A TROPICAL STORM WITH ITS 
BROAD RAIN BANDS TRAILING SOUTHWESTWARD ALL THE WAY TO BORNEO. THE 
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON A RAGGED 
BUT DEFINED LLC FEATURE IN THE 142155Z SSMIS, THE INTENSITY IS 
ASSESSED WITH HIGH CONFIDENCE FROM 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). 
THE SYSTEM IS ALSO TAPPING INTO A POLEWARD OUTFLOW CHANNEL EMANATING 
FROM A TUTT TO THE NORTHWEST, ALSO EVIDENT IN THE EIR LOOP.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA.

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 31 KTS AT 142330Z
   CIMSS D-PRINT: 37 KTS AT 150100Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD 04W WILL CONTINUE TO TRACK GENERALLY
WEST-NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE STR, OVER THE 
WARM SCS, MAKE LANDFALL ON THE LEIZHOU PENINSULA NEAR ZHANJIANG 
BEFORE TAU 60, AND CROSS THE GULF OF TONKIN BEFORE MAKING A FINAL 
LANDFALL ALONG THE VIETNAM-CHINA BORDER AFTER TAU 72. THE FAVORABLE 
ENVIRONMENT WILL FUEL SIGNIFICANT INTENSIFICATION TO A PEAK OF 90KTS 
AT TAU 48. LAND INTERACTION WITH RUGGED TERRAIN WILL MOSTLY BE 
RESPONSIBLE FOR THE GRADUAL THEN RAPID EROSION AFTER TAU 48, LEADING 
TO DISSIPATION BY TAU 120 AS IT TRACKS DEEP INTO THE CHINESE 
INTERIOR.   


MODEL DISCUSSION: THERE IS OVERALL GOOD AGREEMENT AMONG THE
NUMERICAL TRACK MODELS WITH AN EVEN AND GRADUAL SPREAD TO A MERE 
158NM BY TAU 72. AFTERWARD, THE TRACKERS SIGNIFICANTLY SPREAD OUT TO 
670NM+ BY TAU 120, AN INDICATION OF A WEAK VORTEX, LENDING 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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