WDXS32 PGTW 210900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 15S (EWETSE) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.3S 43.4E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 217 NM SOUTHEAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 15S (EWETSE) JUST OFF THE SOUTHWESTERN COAST OF MADAGASCAR
WITH A DECOUPLED AND ELONGATED LOW-LEVEL CIRCULATION CENTER (LLCC).
THE REMNANT CONVECTION HAS STARTED TO DRIFT OFF TO THE SOUTHEAST,
AWAY FROM THE SYSTEM, LEAVING BEHIND A SHALLOW VORTEX.
ENVIRONMENTAL ANALYSIS INDICATES THAT 15S IS NOW IN A MARGINALLY
UNFAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD OUTFLOW
AND WARM (28-29 C) SEA SURFACE TEMPERATURES GREATLY OFFSET BY
MODERATE TO HIGH (20-25 KTS) NORTHWESTERLY VERTICAL WIND SHEAR, DRY
AIR ENTRAINMENT, AND TERRAIN INTERACTION. THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON THE MOSTLY EXPOSED LLCC IN
ANIMATED MSI. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: LOW-LEVEL WESTERLY FLOW ON THE
EQUATORWARD SIDE OF A SHEAR LINE

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   DEMS: T3.0 - 45 KTS
   FMEE: T2.5 - 35 KTS
   CIMSS ADT: 47 KTS AT 210600Z
   CIMSS AIDT: 44 KTS AT 210515Z
   CIMSS D-MINT: 33 KTS AT 210325Z
   CIMSS D-PRINT: 32 KTS AT 210630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE NORTH AND TERRAIN
INTERACTION WITH SOUTHWESTERN MADAGASCAR

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 15S IS FORECAST TO DRIFT NORTHEASTWARD INTO
SOUTHWESTERN MADAGASCAR OVER THE NEXT 12 HOURS. AFTER MAKING
LANDFALL, THE REMNANT VORTEX IS FORECAST TO DEFLECT NORTHWARD DUE
TO THE MOUNTAINOUS TERRAIN OF SOUTHERN MADAGASCAR. 15S WILL RAPIDLY
WEAKEN OVER THE NEXT 24 HOURS DUE TO INCREASING DRY AIR ENTRAINMENT
FROM THE WEST AND TERRAIN INTERACTION. DISSIPATION IS EXPECTED TO
OCCUR NO LATER THAN TAU 24. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT WITH A 150 NM CROSS-TRACK SPREAD AT TAU 24. ECMWF IS THE
NORTHERNMOST MEMBER, TRACKING THE VORTEX ALONG THE WESTERN COAST OF
MADAGASCAR. ON THE OTHER HAND, UKMET AND GALWEM BOTH TRACK THE
VORTEX ALMOST STRAIGHT EASTWARD. THE JTWC TRACK FORECAST IS HEDGED
CLOSER TO THE ECMWF WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS
IN GOOD AGREEMENT ON STEADY WEAKENING THROUGHOUT THE FORECAST
PERIOD. THE JTWC INTENSITY FORECAST IS PLACED NEAR THE CONSENSUS
WITH HIGH CONFIDENCE.  

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: HIGH//
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