WDXS31 PGTW 242100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04S (CHENGE) WARNING NR 
018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 8.8S 53.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 702 NM NORTH-NORTHEAST OF ANTANANARIVO,
MADAGASCAR
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WHICH IS
TILTED WESTWARD BY STRONG 20-25KT VERTICAL WIND SHEAR.  DESPITE THE
EASTERLY SHEAR, OUTFLOW REMAINS RADIAL ALOFT. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON A 241724Z METOP-B MHS 89GHZ
MICROWAVE IMAGE DEPICTING A PARTIALLY EXPOSED LLCC ALONG WITH THE
AFOREMENTIONED ANIMATED EIR. THE INITIAL INTENSITY OF 35 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE
FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE TO THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   DEMS: T3.0 - 45 KTS
   FMEE: T2.5 - 35 KTS
   CIMSS SATCON: 41 KTS AT 241453Z
   CIMSS ADT: 32 KTS AT 241800Z
   CIMSS AIDT: 35 KTS AT 241700Z
   CIMSS D-MINT: 36 KTS AT 241452Z
   CIMSS D-PRINT: 37 KTS AT 241800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: LOW
   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 CYCLONE (TC) 04S WILL CONTINUE ON A
WESTWARD TRACK FOR THE REMAINDER OF THE FORECAST PERIOD WHILE
REMAINING UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGE TO
THE SOUTH. THE SYSTEM WILL WEAKEN GRADUALLY OVER THE NEXT 36 HOURS
AS VERTICAL WIND SHEAR REMAINS HIGH THROUGHOUT THE FORECAST,
CAUSING TC 04S TO BECOME SHALLOW AND DRY. BY THE END OF THE FORECAST 
AT TAU 48, TC 04S WILL HAVE DISSIPATED OVER WATER BELOW WARNING
THRESHOLD. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
THAT TC 04S WILL TRACK BETWEEN WEST-NORTHWESTWARD AND WESTWARD FOR
THE REMAINDER OF THE FORECAST PERIOD. THE CROSS-TRACK SPREAD BY THE
END OF THE FORECAST IS 72 NM, SUPPORTING THE HIGH CONFIDENCE IN THE
NEAR-TERM TRACK FORECAST.  THE INTENSITY GUIDANCE IS ALSO IN GOOD
AGREEMENT THAT TC 04S WILL REMAIN AT OR SLIGHTLY ABOVE 35KTS FOR
THE NEXT 24-36 HOURS BEFORE REACHING DISSIPATION BY TAU 36-48. 

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