WDXS31 PGTW 140900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04S (CHIDO) 
WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.6S 45.4E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 397 NM NORTH-NORTHWEST OF ANTANANARIVO,
MADAGASCAR
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 04S (CHIDO) WITH A VERY COMPACT, SYMMETRICAL CENTRAL
DENSE OVERCAST AND AN EYE THAT IS PARTIALLY CLOUD-FILLED. THE
PERSISTENT EASTERLY VERTICAL WIND SHEAR HAS APPEARED TO LESSEN OVER
THE PAST 6 HOURS. O4S IS TRACKING DIRECTLY OVER THE ISLAND OF
MAYOTTE AS IT CONTINUES ITS WEST-SOUTHWESTWARD TRACK. ENVIRONMENTAL
ANALYSIS INDICATES THAT 04S IS IN A FAVORABLE ENVIRONMENT
CHARACTERIZED BY MODERATE RADIAL OUTFLOW ALOFT, LOW TO MODERATE
(15-20 KTS) VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE
TEMPERATURES. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED
ON THE EYE IN THE ANIMATED MSI. THE INITIAL INTENSITY OF 115 KTS IS
ASSESSED WITH LOW CONFIDENCE BASED ON THE DISPARITY BETWEEN THE
AGENCY DVORAK ESTIMATES, OBJECTIVE ESTIMATES, AND AN EARLIER
(AROUND 1500Z) SAR IMAGE. THE SAR IMAGE SHOWED A VMAX OF 130 KTS,
AND THE OVERALL APPEARANCE OF THE SYSTEM IS SIMILAR, IF EVEN
SLIGHTLY BETTER SINCE THEN. THE AGENCY AND OBJECTIVE ESTIMATES ARE
MUCH LOWER, RANGING FROM 97-102 KTS. DUE TO THE COMPACT NATURE OF
THE SYSTEM, THE DVORAK ESTIMATES COULD BE UNDERESTIMATING
INTENSITY. THE INITIAL INTENSITY IS THEREFORE HEDGED HIGHER THAN
THE DVORAK ESTIMATES, BUT WITHOUT FULLY LEANING INTO THE 130 KNOT
SYSTEM THAT THE SAR IMAGE SUGGESTED DUE TO THE SLIGHTLY RAGGED EYE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: THE NORTHWESTERN PERIPHERY OF A
DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   KNES: T5.5 - 102 KTS
   DEMS: T5.5 - 102 KTS
   FMEE: T5.5 - 102 KTS
   CIMSS ADT: 97 KTS AT 140600Z
   CIMSS AIDT: 100 KTS AT 140600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 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: 04S IS FORECAST TO CONTINUE TRACKING GENERALLY
WEST-SOUTHWESTWARD ALONG THE NORTHWESTERN PERIPHERY OF THE STR
CENTERED TO THE SOUTHEAST THROUGH THE REMAINDER OF THE FORECAST
PERIOD. LANDFALL ALONG THE COAST OF NORTHERN MOZAMBIQUE IS EXPECTED
TO OCCUR RIGHT AROUND TAU 24, ABOUT 35 NM SOUTH OF THE PEMBA BAY
AREA. AFTER TAU 24, 04S IS FORECAST TO CONTINUE TRACKING FURTHER
INLAND, TOWARDS THE SOUTHERN TIP OF LAKE MALAWI AS IT DISSIPATES.
REGARDING INTENSITY, 04S IS FORECAST TO MAINTAIN OR EVEN SLIGHTLY
INTENSIFY OVER THE NEXT 12-18 HOURS BEFORE IT MAKES LANDFALL. THE
ENVIRONMENT WILL REMAIN CONDUCIVE AS POLEWARD OUTFLOW INCREASES AND
SEA SURFACE TEMPERATURES REMAIN VERY WARM. AFTER MAKING LANDFALL,
TERRAIN INTERACTION WILL QUICKLY ERODE THE VORTEX, CAUSING RAPID
WEAKENING. DISSIPATION IS EXPECTED TO OCCUR NO LATER THAN TAU 48.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO BE IN TIGHT
AGREEMENT REGARDING THE TRACK OF 04S THROUGHOUT THE FORECAST
PERIOD. AS A RESULT, THE JTWC TRACK FORECAST IS PLACED CLOSE TO
CONSENSUS WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD
AGREEMENT, WITH THE EXCEPTION OF GFS WHICH HAS THE SYSTEM MUCH
WEAKER THAN THE MESOSCALE MODELS. THE JTWC INTENSITY FORECAST IS
PLACED CLOSE TO COAMPS-TC, HWRF, AND HAFS-A THROUGHOUT THE FORECAST
WITH MEDIUM CONFIDENCE DUE TO THE LOW CONFIDENCE IN INITIAL
INTENSITY. 

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