WDPN31 PGTW 221500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 30W (FENGSHEN) WARNING 
NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.2N 109.6E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 104 NM NORTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
OVER THE PAST 6 HOURS TROPICAL STORM (TS) 30W (FENGSHEN) HAS
WEAKENED FROM PROLONGED EXPOSURE TO HIGH VERTICAL WIND SHEAR (15-20
KTS) AND RELATIVELY DRIER AIR BEING WRAPPED IN FROM THE WESTERN
SEMICIRCLE OF THE SYSTEM. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY DEPICTS TEMPERATURES WITHIN THE CIRCULATION HAS
WARMED SIGNIFICANTLY AND THE SYSTEM HAS LOST NEARLY ALL ASSOCIATED
CONVECTIVE ACTIVITY WITH REMAINING POCKETS OF MOISTURE DISPLACED
FROM THE CENTER OF CIRCULATION.  THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON THE EIR SATELLITE IMAGERY AND AGENCY
FIXES. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON MULTI-AGENCY SUBJECTIVE DVORAK AND AUTOMATED
INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T3.5 - 55 KTS
   CIMSS SATCON: 45 KTS AT 221023Z
   CIMSS ADT: 33 KTS AT 221130Z
   CIMSS AIDT: 34 KTS AT 221130Z
   CIMSS D-MINT: 41 KTS AT 221022Z
   CIMSS D-PRINT: 39 KTS AT 221200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TS FENGSHEN WILL CONTINUE WEST-SOUTHWESTWARD
FOR THE REMAINDER OF THE FORECAST PERIOD DRIVEN BY THE SUBTROPICAL
RIDGE TO THE NORTHWEST. CONTINUED WEAKENING IS EXPECTED AS SHEAR
PEELS APART THE STRUCTURE, WHILE COOL, DRY AIR BECOMES MORE
ENTRAINED INTO THE SYSTEM. TS FENGSHEN WILL APPROACH THE COAST OF
VIETNAM AS A WEAK TROPICAL STORM AFTER TAU 12. THE SYSTEM IS
EXPECTED TO FULLY DISSIPATE OVER LAND BY TAU 36.

MODEL DISCUSSION: CROSS TRACK SPREAD IS UNDER 70 NM THROUGH TAU 24,
WITH THE SPREAD ENVELOPE INCREASING TO AROUND 90 NM AFTERWARDS. THE
JTWC OFFICIAL TRACK IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH 
HIGH 
CONFIDENCE. INTENSITY GUIDANCE SPREAD IS BETWEEN 5-10 KTS UNTILL TAU 
24. THE
SPREAD INCREASES TO 15 KTS AFTERWARD AS A RESULT OF LAND INTERACTION. 
THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO THE MULTI-MODEL 
CONSENSUS WITH 
HIGH CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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