WDXS31 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04S (CHIDO) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.5S 58.4E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 579 NM NORTH OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 04S (CHIDO) WITH A NEWLY DEVELOPED EYE-FEATURE AND AN
INCREASINGLY SYMMETRIC STRUCTURE WITH SUPPORTIVE CURVED CONVECTIVE
BANDING WRAPPING NEATLY AROUND THE ENTIRETY OF THE SYSTEM'S
PERIPHERY. ON ANIMATED WATER VAPOR IMAGERY, MODERATE RADIAL OUTFLOW
HAS ALSO BEEN OBSERVED OVER THE LAST FEW HOURS, BURSTING OUTWARD
FROM THE CENTER AS CONVECTIVE STRUCTURES CONTINUE TO WRAP TIGHTLY
AROUND THE AFOREMENTIONED EYE-FEATURE. THE ENVIRONMENT HAS REMAINED
LARGELY CONDUCIVE FOR FURTHER INTENSIFICATION, AS VERTICAL WIND
SHEAR (VWS) REMAINS LOW, BETWEEN 10-15 KTS, AND SEA SURFACE
TEMPERATURES (SST) CONTINUE BETWEEN 28-29 C. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON THE VISIBLE EYE-FEATURE ON
ANIMATED EIR IMAGERY AND A 110538Z METOP-B SCATTEROMETRY IMAGE. THE
INITIAL INTENSITY OF 75 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON MULTI-AGENCY SATELLITE FIXES RANGING BETWEEN 65 KTS AND 77
KTS, AND AUTOMATED CIMSS OBJECTIVE ESTIMATES BETWEEN 59 KTS AND 75
KTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   DEMS: T4.0 - 65 KTS
   FIMP: T4.5 - 77 KTS
   CIMSS ADT: 59 KTS AT 110630Z
   CIMSS AIDT: 75 KTS AT 110630Z
   CIMSS D-PRINT: 61 KTS AT 110630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 04S IS FORECASTED TO CONTINUE TRACKING
WESTWARD THROUGH THE NEXT 24 HOURS ALONG THE NORTHERN PERIPHERY OF
THE SUBTROPICAL RIDGE DIRECTLY TO THE SOUTH. AFTER TAU 24, THE
SYSTEM IS EXPECTED TO BEGIN ITS WEST-SOUTHWEST TREK TOWARD THE
NORTHERN TIP OF MADAGASCAR ALONG THE NORTHWEST PERIPHERY OF A
WESTWARD BUILDING RIDGE. AS TC 04S TRACKS PAST MADAGASCAR NEAR TAU
72, THE SYSTEM WILL CONTINUE WEST-SOUTHWESTWARD SOUTH OF NACALA,
MOZAMBIQUE AT TAU 100. AFTER TAU 100, THE SYSTEM IS FORECASTED TO
MAKE LANDFALL UNTIL THE END OF THE FORECAST PERIOD. WITH REGARD TO
INTENSITY, A LARGELY CONDUCIVE ENVIRONMENT FRAMED WITH LOW VWS AND
WARM SSTS WILL ALLOW FOR RAPID INTENSIFICATION OVER THE NEXT 24
HOURS, INCREASING INTENSITIES FROM 75 KTS TO 110 KTS. AFTER TAU 24
AND AS THE SYSTEM BEGINS ITS WEST-SOUTHWEST TRACK TOWARD
MADAGASCAR, EASTERLY VWS IS EXPECTED TO INCREASE WHILE
OPPORTUNITIES FOR OUTFLOW ALOFT DIMINISH, BEGINNING THE INITIAL
WEAKENING PHASE. JUST BEFORE TAU 72, INTERACTION WITH MADAGASCAR'S
TERRAIN WILL FURTHER WEAKEN TC 04S TO AROUND 70 KTS. FOLLOWING TAU
72, SUSTAINED EASTERLY VWS FROM THE ASSOCIATED RIDGING TO THE SOUTH
WILL CONTINUE TO ERODE TC CHIDO THROUGH LANDFALL NEAR TAU 100.
FOLLOWING LANDFALL SOUTH OF NACALA AT TAU 100, THE SYSTEM IS
FORECASTED TO DISSIPATE BY TAU 120 TO LESS THAN 35 KTS.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT FOR
THE TRACK OF 04S THROUGH TAU 72 WITH A CROSS-TRACK SPREAD OF 124
NM. FOLLOWING TAU 72, THE CROSS-TRACK SPREAD BEGINS TO INCREASE
WITH ENHANCED INFLUENCES FROM THE BUILDING SUBTROPICAL RIDGE TO THE
SOUTH UNTIL THE END OF THE FORECAST PERIOD. WITH THAT BEING SAID, ALL 
DETERMINISTIC AND ENSEMBLE MEAN MEMBERS CONTINUE TO SHOW A GENERAL 
WEST-SOUTHWESTWARD TRACK THROUGHOUT THE FORECAST PERIOD, WITH THE 
EXCEPTION OF NAVGEM, WHICH INDICATES A RECURVE SCENARIO SOUTHWEST OF 
MADAGASCAR AFTER TAU 72. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT 
THAT INTENSIFICATION IS EXPECTED OVER THE NEXT 24 HOURS WITH A SLOW 
BUT STEADY WEAKENING TREND THEREAFTER. ADDITIONALLY, COAMPS-TC EPS 
INTENSITY PROBABILITIES INDICATE A 30 PERCENT CHANCE OF RAPID 
INTENSIFICATION OVER THE NEXT 24-36 HOURS, WITH A MODERATE WEAKENING 
PHASE EXPECTED THEREAFTER. THE JTWC INTENSITY FORECAST IS ALIGNED 
WITH THE MULTI-MODEL INTENSITY 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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