WDXS31 PGTW 222100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04S (CHENGE) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.4S 60.5E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 611 NM NORTH-NORTHEAST OF PORT LOUIS,
MAURITIUS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH
STRUGGLING CONVECTION SHEARED TO THE WEST-SOUTHWEST. THE STORM IS
STRUGGLING TO MAINTAIN STRUCTURE AGAINST THE MODERATE TO HIGH
(20-25 KTS) EASTERLY VERTICAL WIND SHEAR AND DRY AIR FROM THE EAST
ENTRAINING INTO THE CORE. A 221438Z 91GHZ SSMIS IMAGE REVEALS THAT
THE UPPER-LEVEL CENTER IS DISPLACED TO THE WEST OF THE LOW-LEVEL
CENTER. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED
ON THE PARTIALLY EXPOSED LLCC AND EXTRAPOLATION FROM THE
PREVIOUSLY MENTIONED 221438Z 91GHZ SSMIS IMAGE. THE INITIAL
INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
AUTOMATED OBJECTIVE INTENSITY ESTIMATES AND AGENCY DVORAK FIXES
LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   CIMSS ADT: 51 KTS AT 221900Z
   CIMSS AIDT: 42 KTS AT 221900Z
   CIMSS D-MINT: 41 KTS AT 221914Z
   CIMSS D-PRINT: 49 KTS AT 221900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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 CYCLONE (TC) 04S (CHENGE) WILL
CONTINUE ALONG A WESTWARD TRACK AS IT REMAINS UNDER THE STEERING
INFLUENCE OF THE STR TO ITS SOUTHEAST FOR THE NEXT 24 HOURS.
BEGINNING AROUND TAU 24, THE STEERING STR WILL BUILD AND EXTEND
WESTWARD, CAUSING 04S TO ASSUME A WEST-NORTHWESTWARD TRAJECTORY,
WHICH WILL CONTINUE FOR THE REMAINDER OF THE FORECAST PERIOD.
LANDFALL IS FORECAST NEAR DAR ES SALAAM, TANZANIA AROUND TAU 102.
THE ENVIRONMENT WILL REMAIN MARGINALLY UNFAVORABLE OVER THE
FORECAST DURATION, STIFLING CHANCES FOR REINTENSIFICATION.
SIGNIFICANT DRY AIR ENTRAINMENT ALONG THE EASTERN FLANK AND EASTERLY
VERTICAL WIND SHEAR WILL CONTINUE TO PUMMEL CHENGE, LEADING IT TO
SLOWLY BUT STEADILY WEAKEN, WITH DISSIPATION FORECAST OVER WATER
BETWEEN TAU 96-120. 

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE IS IN GOOD
AGREEMENT THAT 04S WILL TRACK GENERALLY WEST-NORTHWESTWARD OVER THE
FORECAST PERIOD, WITH MARGINAL DISAGREEMENT IN ALONG-TRACK SPEED
AND LANDFALL LOCATION, LENDING MINOR UNCERTAINTY TO THE JTWC TRACK
FORECAST. AS A RESULT, THE JTWC TRACK FORECAST IS PLACED WITH HIGH
CONFIDENCE FROM TAU 0-72, AND MEDIUM CONFIDENCE FROM TAU 72-120.
RELIABLE INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT, WITH ALL
MODELS SIGNALING A GRADUAL TERMINAL WEAKENING WITH DISSIPATION
AROUND TAU 96. THE JTWC INTENSITY FORECAST LIES IN CLOSE
CONCURRENCE WITH THE MULTI-MODEL INTENSITY CONSENSUS WITH OVERALL
HIGH CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: HIGH
   INTENSITY 72-120 HR: HIGH//
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