WDXS31 PGTW 181500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (EMNATI) WARNING 
NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.4S 61.3E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 412 NM NORTHEAST OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THE CENTRAL 
CONVECTION HAS SIGNIFICANTLY DEEPENED AND BECOME MORE SYMMETRICAL AS 
CONVECTIVE BANDS WRAPPED TIGHTER INTO AN OBSCURED LOW LEVEL 
CIRCULATION OVER THE LAST 12 HRS. THE INITIAL POSITION IS PLACED 
WITH HIGH CONFIDENCE BASED ON A MICROWAVE EYE IN THE 180951Z AMSR2 
37GHZ IMAGE. THE INITIAL INTENSITY OF 75KTS IS BASED ON AN OVERALL 
ASSESSMENT OF AGENCY AND AUTOMATED DVORAK ESTIMATES (SEE BELOW) AND 
REFLECTS THE 12-HR CONVECTIVE IMPROVEMENT. ANALYSIS INDICATES A 
HIGHLY FAVORABLE ENVIRONMENT WITH WARM ALONG-TRACK SST, STRONG 
RADIAL OUTFLOW AND LIGHT VWS ALOFT. THE CYCLONE 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: T4.0 - 65 KTS
   FIMP: T4.5 - 77 KTS
   CIMSS SATCON: 78 KTS AT 180911Z
   CIMSS ADT: 67 KTS AT 180915Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 EMNATI WILL CONTINUE ON ITS CURRENT
WEST-SOUTHWESTWARD TRACK THROUGHOUT THE FORECAST EVEN AFTER A
SECONDARY STR APPROACHING FROM THE SOUTHWEST SEAMLESSLY ASSUMES
STEERING AFTER TAU 36. SHORTLY AFTER TAU 96, IT WILL MAKE LANDFALL
OVER THE CENTRAL MADAGASCAR COAST EAST OF ANTANANARIVO. THE HIGHLY 
FAVORABLE ENVIRONMENT IS EXPECTED TO CARRY THROUGH THE MID-PORTION 
OF THE FORECAST TRACK AND FUEL STEADY INTENSIFICATION TO A PEAK OF 
100KTS
BY TAU 48. AFTERWARD, LOW OCEAN HEAT CONTENT NEAR MADAGASCAR WILL
CONTRIBUTE TO A GRADUAL WEAKENING - DOWN TO 80KTS BY TAU 96. AFTER
LANDFALL, THE RUGGED TERRAIN WILL RAPIDLY ERODE THE SYSTEM DOWN TO
40KTS BY TAU 120 AS IT APPROACHES THE SOUTHWESTERN COAST OF THE
ISLAND.  

MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY GOOD AGREEMENT WITH
NAVGEM THE SOLE LEFT-OF-TRACK OUTLIER, LENDING HIGH CONFIDENCE IN
THE JTWC TRACK FORECAST THAT IS LAID JUST TO THE RIGHT OF THE MODEL
CONSENSUS TO OFFSET NAVGEM UP TO TAU 72 THEN MEDIUM CONFIDENCE
AFTERWARD AS THE VORTEX TRACKS OVER MADAGASCAR. 

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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