WDXS31 PGTW 212100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (EMNATI) WARNING 
NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.5S 52.1E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 217 NM WEST-NORTHWEST OF ST DENIS
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS
INDICATES TC 13S IS STILL UNDERGOING AN EYEWALL REPLACEMENT CYCLE
AS THERE IS STILL EVIDENCE OF AN INNER EYEWALL WITH A 10NM WIDE EYE
AND AN ILL-DEFINED OUTER EYEWALL. AN 211804Z PARTIAL ASCAT-B IMAGE
SHOWS 40 KT WINDS IN THE OUTER WIND FIELD NOW OVER THE COAST OF
MADAGASCAR NEAR TOAMASINA. THE INITIAL POSITION IS BASED ON THE EYE
OBSERVED IN EIR AND THE INITIAL INTENSITY OF 95 KTS IS AVERAGED
BETWEEN AGENCY CURRENT DVORAK INTENSITY ESTIMATES AND ADT BASED ON
PROBABLE WEAKENING DUE TO THE EYEWALL REPLACEMENT CYCLE. SINCE TC
13S IS ALREADY EXPERIENCING LAND INTERACTION, INTENSIFICATION DUE
TO THE CONSTRICTION OF THE OUTER EYEWALL IS UNLIKELY BEFORE
LANDFALL.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A SUBTROPICAL
RIDGE TO THE SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   FMEE: T5.0 - 90 KTS
   CIMSS SATCON: 104 KTS AT 211611Z
   CIMSS ADT: 102 KTS AT 211515Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: EYEWALL REPLACEMENT CYCLE AND UPWELLING OF COOLER
WATER WITH LOW OCEAN HEAT CONTENT. 

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 13S WILL CONTINUE TRACKING SOUTHWESTWARD,
UNDER THE INFLUENCE OF A SUBTROPICAL RIDGE, DOWN THE EASTERN COAST
OF MADAGASCAR WITH THE CENTER OF THE CIRCULATION MAKING LANDFALL
JUST AFTER TAU 24. THIS LAND INTERACTION WILL CAUSE A DECREASE TO
55 KTS IN INTENSITY BY TAU 48. SHORTLY AFTER, THE SYSTEM WILL
EMERGE BACK OVER WATER INTO COOLER SEA SURFACE TEMPERATURES (26C)
WHICH WILL NOT ALLOW FOR REINTENSIFICATION. BY TAU 72, TC 13S WILL
BEGIN TO TURN POLEWARD INTO A BREAK IN THE SUBTROPICAL RIDGE CAUSED
BY AN APPROACHING MID-LATITUDE TROUGH AND BEGIN SUBTROPICAL
TRANSITION, WHICH IS EXPECTED TO BE COMPLETED BY TAU 96 AT AN
INTENSITY OF 45 KTS.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT IN REGARDS
TO TRACK FORECAST WITH ONLY A 90NM CROSS-TRACK SPREAD AT TAU 72,
EXCLUDING NVGM AS AN OUTLIER SLIGHTLY TO THE NORTH. INTENSITY
GUIDANCE IS ALSO IN GOOD AGREEMENT WITH ALL MODELS EITHER
MAINTAINING CURRENT INTENSITY OR WEAKENING THE SYSTEM BEFORE
LANDFALL. NO MODELS INDICATE REINTENSIFICATION ONCE BACK OVER
WATER.

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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