WDXS31 PGTW 102100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04S (CHIDO) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.6S 59.6E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 585 NM NORTH-NORTHEAST OF PORT LOUIS,
MAURITIUS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN
ASYMMETRIC DEEP CONVECTION PERSISTING OVER A LOW-LEVEL CIRCULATION
CENTER EVIDENT IN A 101653Z METOP-B ASCAT PASS. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON MULTI-AGENCY
SATELLITE FIXES AND THE AFOREMENTIONED ASCAT DATA. THE INITIAL
INTENSITY OF 60 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
AVAILABLE AUTOMATED AND SUBJECTIVE ESTIMATES RANGING FROM 48 KNOTS
TO 65 KNOTS. TC 04S IS SLOWLY INTENSIFYING UNDER THE INFLUENCES OF
MODERATE EASTERLY VERTICAL WIND SHEAR, RADIAL OUTFLOW ALOFT, AND
PASSAGE OVER VERY WARM WATER.

INITIAL WIND RADII BASIS: 101653Z METOP-B ASCAT PASS

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   DEMS: T3.5 - 55 KTS
   CIMSS SATCON: 48 KTS AT 101418Z
   CIMSS ADT: 53 KTS AT 101500Z
   CIMSS AIDT: 60 KTS AT 101700Z
   CIMSS D-MINT: 54 KTS AT 101439Z
   CIMSS D-PRINT: 53 KTS AT 101900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: FORECAST INTENSITIES HAVE INCREASED
FROM THE PREVIOUS WARNING BASED ON EXPECTATIONS OF FAVORABLE
ENVIRONMENTAL SUPPORT. OTHERWISE, THERE ARE NO MAJOR CHANGES.

FORECAST DISCUSSION: TC 04S WILL CONTINUE TRACKING WESTWARD TO
WEST-SOUTHWESTWARD THROUGHOUT THE FORECAST PERIOD DUE TO PERSISTENT
RIDGING TO THE SOUTH OF THE SYSTEM. ENVIRONMENTAL CONDITIONS TO
THIS POINT HAVE FAVORED SLOW DEVELOPMENT, BUT OVER THE NEXT 12 TO
24 HOURS, VERTICAL WIND SHEAR IS EXPECTED TO DECREASE AND UPPER-LEVEL
OUTFLOW IS EXPECTED TO IMPROVE MARKEDLY, WITH LIKELY DEVELOPMENT OF
A POLEWARD OUTFLOW CHANNEL ENHANCED TOWARD AN UPPER-LEVEL SHORTWAVE
TROUGH PASSING TO THE SOUTH. TC 04S IS EXPECTED TO STEADILY
INTENSIFY, PERHAPS RAPIDLY, THROUGH TAU 36 UNDER THESE FAVORABLE
CONDITIONS. THEREAFTER, EASTERLY VERTICAL WIND SHEAR IS EXPECTED TO
INCREASE AND OUTFLOW DIMINISH AS THE FLOW ASSOCIATED WITH A
BUILDING DEEP-LAYER RIDGE TO THE SOUTH IMPACTS THE SYSTEM.
INTERACTION WITH THE NORTHERN PORTION OF MADAGASCAR WILL ACCELERATE
WEAKENING AROUND TAU 72 AND THE SYSTEM IS LIKELY TO WEAKEN ONLY
SLOWLY THEREAFTER AS IT MOVES WEST-SOUTHWARD TOWARD LANDFALL IN
MOZAMBIQUE NEAR THE END OF THE FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL MODELS GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE TRACK OF 04S THROUGH TAU 72, WITH SPREAD INCREASING
IN THE EXTENDED TAUS. ALL DETERMINISTIC AND ENSEMBLE MEAN
TRACKERS, ASIDE FROM NAVGEM, DEPICT A CONTINUOUS WESTWARD TO
WEST-SOUTHWESTWARD TRACK THROUGH THE ENTIRETY OF THE FORECAST
PERIOD. NAVGEM DEPICTS RECURVATURE OVER MADAGASCAR, WHICH IS ASSESSED 
AS A VERY UNLIKELY SCENARIO THAT NONE OF THE GEFS OR ECMWF MEDIUM-
RANGE ENSEMBLE SOLUTIONS SUPPORT. INTENSITY MODELS ARE IN GOOD 
AGREEMENT REGARDING THE TREND TOWARD A PEAK INTENSITY AT TAU 36 WITH A 
SLOW TO STEADY WEAKENING THEREAFTER. HOWEVER, SOLUTIONS FOR PEAK 
INTENSITY RANGE FROM 90 TO AS HIGH AS 140 KTS (HAFS). THE CURRENT 
INTENSITY FORECAST IS CONSISTENT WITH THE MULTI-MODEL CONSENSUS.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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