WDPN31 PGTW 202100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (FOUR) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.3N 111.5E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 185 NM EAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY INDICATES
TROPICAL STORM 04W IS DEVELOPING VERY SLOWLY WITHIN THE MONS0ON
TROF DESPITE THE LOW VERTICAL WINDSHEAR AND HEAVY SATURATION OF ITS 
ENVIRONMENT. THE SYSTEM IS ASYMMETRICAL AND TILTED VERTICALLY. THE 
BROAD LOW LEVEL CIRCULATION CENTER (LLCC) IS DUCKING IN AND OUT OF 
THE CONVECTIVE SHIELD AND AT TIMES BECOMING PARTLY EXPOSED. A 201748Z 
AMSR2 SERIES CONFIRMS DEEP CONVECTIVE BANDING IN ALL BUT THE 
SOUTHEAST QUADRANT AND AIDS IN PLACEMENT, FITTING NICELY WITH THE 
AGENCY FIXES. THE INTENSITY ASSESSMENT IS WEIGHTED TOWARDS OBJECTIVE 
DVORAKS FROM ADT AND SATCON BASED ON THE MICROWAVE SIGNATURE. OUTFLOW 
IS DECENT BUT NOTHING SPECTACULAR DESPITE THERE BEING NO IMPINGEMENTS 
IN ANY QUADRANT.

INITIAL WIND RADII BASIS: ESTIMATED BASED ON CONVECTIVE BANDING. 

CURRENT STEERING MECHANISM: THE SOUTHEASTERN FLANK OF THE
SUBTROPICAL RIDGE. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS SATCON: 40 KTS AT 1900Z
   CIMSS ADT: 34 KTS AT 1930Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 9 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 04W WILL STEAM ALONG THE
SOUTHEASTERN FLANK OF THE SUBTROPICAL RIDGE AND INTENSIFY SLOWLY
UNTIL IT MAKES LANDFALL OVER THE SOUTHEASTERN COAST OF HAINAN JUST
PRIOR TO TAU 48. EXPECTED INTENSITY AT LANDFALL IS AT OR BELOW
50KTS. THE RICH MOISTURE AND LOW VERTICAL WINDSHEAR OF ITS CURRENT
ENVIRONMENT COUPLED WITH THE WARM WATERS OF THE GULF OF TONKIN WILL
AID IN REGENERATION PRIOR TO THE SYSTEM'S SECOND LANDFALL, BUT
VERTICAL WINDSHEAR INCREASES SHARPLY OVER THE GULF OF TONKIN SO THE
SYSTEM WILL NOT RISE MUCH ABOVE GALE FORCE. 

MODEL DISCUSSION: MODEL GUIDANCE HAS BEEN STEADY AND CONSISTENT
WITH TS 04W. THE JTWC FORECAST STAYS CLOSE TO THE MULTI-MODEL
CONSENSUS WITH BOTH TRACK AND INTENSITY. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
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