WDXS31 PGTW 131500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04S (CHIDO) WARNING NR 
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.6S 48.8E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 444 NM NORTH OF ANTANANARIVO, MADAGASCAR
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 04S (CHIDO) WITH A NOW CLOUD-FILLED EYE, HOWEVER, THE
EYE WAS BRIEFLY CLEARED OUT AROUND 0900Z-1130Z. THE CENTRAL DENSE
OVERCAST REMAINS VERY COMPACT AND SYMMETRICAL AS THE SYSTEM PASSES
BY THE NORTHERN TIP OF MADAGASCAR, ABOUT 35 NM OFF THE COAST.
ENVIRONMENTAL ANALYSIS INDICATES THAT 04S IS IN A MARGINALLY
FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE RADIAL OUTFLOW
ALOFT, 15-20 KTS OF EASTERLY VERTICAL WIND SHEAR, AND WARM (28-29
C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE EYE FEATURE IN ANIMATED MSI. THE
INITIAL INTENSITY OF 105 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE AGENCY DVORAK CURRENT INTENSITY ESTIMATES RANGING FROM
T5.0-T6.0.

INITIAL WIND RADII BASIS: PERSISTENCE 

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: T5.0 - 90 KTS
   DEMS: T6.0 - 115 KTS
   FMEE: T5.5 - 102 KTS

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: LOW

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 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. 04S IS EXPECTED TO PASS OVER, OR JUST NORTH OF
MAYOTTE AROUND TAU 18 AND THEN HEAD TOWARD THE COAST OF NORTHERN
MOZAMBIQUE. LANDFALL LOCATION HAS SLIGHTLY SHIFTED SOUTH SINCE THE
PREVIOUS FORECAST AND IS NOW ABOUT 25 NM SOUTH OF PEMBA BAY. AFTER
MAKING LANDFALL, THE SYSTEM WILL TRACK TOWARDS THE SOUTHERN TIP OF
LAKE MALAWI AS IS DISSIPATES. REGARDING INTENSITY, 04S IS FORECAST
TO GENERALLY MAINTAIN INTENSITY THROUGH TAU 36 AS THE ENVIRONMENT
WITHIN THE MOZAMBIQUE CHANNEL IS EXPECTED TO BE FAVORABLE. IN
PARTICULAR, POLEWARD OUTFLOW WILL INCREASE AND SEA SURFACE
TEMPERATURES WILL RISE TO AROUND 30C. DUE TO THE FAVORABLE
CONDITIONS, THERE IS A POSSIBILITY FOR A SLIGHT REINTENSIFICATION
PHASE BEFORE MAKING LANDFALL. AFTER MAKING LANDFALL, 04S WILL
RAPIDLY WEAKEN AS TERRAIN INTERACTION QUICKLY ERODES THE VORTEX. 
DISSIPATION IS EXPECTED TO OCCUR NO LATER THAN TAU 72. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO BE IN TIGHT
AGREEMENT WITH A 37 NM CROSS-TRACK SPREAD AROUND THE TIME OF
LANDFALL. MODELS SPREAD TO A 109 NM CROSS-TRACK SPREAD AT TAU 72
DUE TO THE WEAKENED VORTEX. 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. HAFS-A
IS THE MOST AGGRESSIVE WHILE GFS AND HWRF ARE MUCH LESS SO. HAFS-A
SUGGESTS A 100-105 KNOT INTENSITY FROM TAU 12 TO 36 WHILE THE GFS
AND HWRF SUGGEST A 70-75 KNOT INTENSITY FOR THE SAME TIME PERIOD.
THE JTWC INTENSITY FORECAST IS PLACED ON THE HIGHER END OF
GUIDANCE, CLOSER TO THE HAFS-A, DUE TO THE EXPECTED FAVORABLE
ENVIRONMENT AS THE SYSTEM TRAVERSES THROUGH THE MOZAMBIQUE CHANNEL.

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