WDXS31 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (EMNATI) WARNING NR 
013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.8S 50.3E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 167 NM EAST-SOUTHEAST OF ANTANANARIVO,
MADAGASCAR
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS THE SYSTEM HAS 
MAINTAINED A 6-NM PINHOLE EYE EVEN AS THE CENTRAL CONVECTIVE TOPS HAVE 
SIGNIFICANTLY WARMED AS THE WESTERN FEEDER BANDS ENCOUNTER THE EASTERN 
COAST OF MADAGASCAR. THE INITIAL POSITION IS PLACED WITH HIGH 
CONFIDENCE BASED ON THE EYE THAT LINED UP WELL WITH A LOW LEVEL 
MICROWAVE EYE FEATURE IN THE 220315Z SSMIS 91GHZ IMAGE. THE INITIAL 
INTENSITY IS BASED ON THE LOWER AND MORE RECENT DVORAK ESTIMATES FROM 
AGENCY AND AUTOMATED SOURCES (SEE BELOW) AND REFLECTS THE RAPID 12-HR 
WEAKENING TREND. ANALYSIS INDICATES A MARGINALLY FAVORABLE ENVIRONMENT 
WITH LOW VWS, WARM SST, AND STRONG RADIAL OUTFLOW OFFSET BY THE 
SIGNIFICANT REDUCTION OF TOTAL PRECIPITABLE WATER AS TC 13S IS ABOUT 
TO MAKE LANDFALL INTO MADAGASCAR. TC 13S IS TRACKING ALONG THE 
NORTHWESTERN PERIPHERY OF THE DEEP LAYER STR TO THE SOUTHEAST.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA.

CURRENT STEERING MECHANISM: DEEP LAYER SUBTROPICAL RIDGE (STR) TO
THE SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   FMEE: T5.0 - 90 KTS
   CIMSS SATCON: 90 KTS AT 220316Z
   CIMSS ADT: 80 KTS AT 220445Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG RADIAL

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 ON ITS CURRENT
SOUTHWESTWARD TRACK UNDER THE STEERING INFLUENCE OF THE STR AND MAKE 
LANDFALL OVER THE SOUTH CENTRAL EASTERN COAST OF MADAGASCAR JUST AFTER 
TAU 12, DRAG ACROSS THE ISLAND, AND EXIT INTO THE MOZAMBIQUE CHANNEL 
NEAR TAU 42, THEN TRACKS SOUTHWARD AS IT ROUNDS THE WESTERN EDGE OF 
THE STR. INTERACTION WITH THE RUGGED TERRAIN, THEN THE COOLER (24C) 
SST AND STRONG (30KT+) VWS IN THE MOZAMBIQUE CHANNEL WILL RESULT IN 
RAPID DECAY - DOWN TO 45KTS BY TAU 72. CONCURRENTLY BY TAU 48, TC 13S
WILL BEGIN SUBTROPICAL TRANSITION AND BY TAU 72, WILL TRANSFORM
INTO A SUBTROPICAL SYSTEM WITH AN EXPANDING WIND FIELD.   

MODEL DISCUSSION: NUMERICAL MODELS ARE GENERALLY IN GOOD AGREEMENT 
WITH NAVGEM THE SOLE RIGHT-OF-TRACK OUTLIER BEYOND TAU 36, INDICATING 
A QUASI-STATIONARY VORTEX. DUE TO THE UNCERTAINTY OF A LAND PASSAGE,
THERE IS OVERALL MEDIUM CONFIDENCE IN THE JTWC TRACK AND INTENSITY
FORECASTS.  

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