WDXS31 PGTW 130900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04S (CHIDO) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.1S 49.9E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 488 NM NORTH-NORTHEAST OF ANTANANARIVO,
MADAGASCAR
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 39 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 04S (CHIDO) WITH A CLOUD-FILLED EYE AND PRESSURE ON
ITS EASTERN SIDE IN RESPONSE TO THE MODERATE EASTERLY SHEAR. THE
CENTRAL DENSE OVERCAST HAS REMAINED COMPACT AND SYMMETRICAL THOUGH.
ENVIRONMENTAL ANALYSIS INDICATES THAT 04S IS IN A MARGINALLY
FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE RADIAL OUTFLOW
ALOFT, 15-20 KTS OF EASTERLY SHEAR, AND WARM (28-29 C) SEA SURFACE
TEMPERATURES. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE EYE FEATURE IN THE ANIMATED MSI. THE INITIAL INTENSITY
OF 105 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
EXTRAPOLATION FROM A PARTIAL 130209Z SEN-1 SAR IMAGE SHOWING A VMAX
OF 110 KNOTS IN THE NORTHEASTERN QUADRANT. THE AGENCY DVORAK
CURRENT INTENSITY (CI) ESTIMATES RANGE FROM 5.5 TO 6.0, FURTHER
SUPPORTING THE INITIAL INTENSITY.

INITIAL WIND RADII BASIS: SAR DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   KNES: T5.5 - 102 KTS
   FMEE: T6.0 - 115 KTS
   CIMSS DMINT: 110 KTS AT 130229Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: INFLOW DISRUPTION DUE TO PROXIMITY TO NORTHERN
MADAGASCAR.

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: A QUICKER WEAKENING TREND OVER LAND
THAN PREVIOUSLY FORECASTED.

FORECAST DISCUSSION: TC 04S IS FORECAST TO TRACK WEST-SOUTHWESTWARD
THROUGH THE REMAINDER OF THE FORECAST PERIOD AS IT TRACKS ALONG THE
NORTHWESTERN PERIPHERY OF THE STR CENTERED TO THE SOUTHEAST. 04S IS
EXPECTED TO TRACK JUST NORTH OF MAYOTTE NEAR TAU 30 AND THEN HEAD
TOWARDS THE COAST OF NORTHERN MOZAMBIQUE WITH LANDFALL FORECAST TO
OCCUR AT TAU 48 NEAR THE PEMBA BAY AREA. 04S WILL THEN MOVE FURTHER
INLAND WITH A POSITION NEAR THE SOUTHERN TIP OF LAKE MALAWI AT THE
END OF THE FORECAST. REGARDING INTENSITY, 04S IS FORECAST TO
GENERALLY MAINTAIN INTENSITY THROUGH TAU 36 AS THE ENVIRONMENT
IMPROVES AND BRIEFLY HALTS THE CURRENT WEAKENING TREND. POLEWARD
OUTFLOW IN PARTICULAR IS EXPECTED TO IMPROVE WITHIN THE MOZAMBIQUE
CHANNEL AND SEA SURFACE TEMPERATURES WILL BE HIGHLY CONDUCIVE.
AFTER THE SYSTEM MAKES LANDFALL, IT WILL RAPIDLY WEAKEN DUE TO
TERRAIN INTERACTION AND DROP TO BELOW 35 KTS AROUND TAU 72.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
REGARDING THE TRACK OF 04S WITH A 40 NM CROSS-TRACK SPREAD AT TAU
48 AND A 68 NM CROSS-TRACK AT TAU 72. THE JTWC TRACK FORECAST IS
PLACED CLOSE TO CONSENSUS WITH HIGH CONFIDENCE. INTENSITY GUIDANCE
IS IN MODERATE AGREEMENT WITH MODELS OVERALL SUGGESTING SLIGHT
WEAKENING OVER THE NEXT 12 HOURS AND THEN A CONSTANT INTENSITY
THROUGH TAU 36 AND RAPID WEAKENING THEREAFTER AS THE SYSTEM MOVES
INLAND. THE JTWC INTENSITY FORECAST IS PLACED ON THE HIGH END OF
GUIDANCE WITH MEDIUM CONFIDENCE DUE TO THE EXPECTED FAVORABLE
ENVIRONMENT AS 04S ENTERS THE MOZAMBIQUE CHANNEL. 

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