WDXS31 PGTW 150900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 12S (DUMAKO) WARNING 
NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.9S 50.4E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 204 NM NORTHEAST OF ANTANANARIVO,
MADAGASCAR
   MOVEMENT PAST 6 HOURS: WESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A VERY
COMPACT SYSTEM WITH WELL ORGANIZED CONVECTIVE BANDS WRAPPING INTO A
SOMEWHAT ELONGATED AND ASYMMETRIC LOW LEVEL CIRCULATION CENTER
(LLCC). A 150210Z SENTINEL-1A SYNTHETIC APERTURE RADAR (SAR) PASS
SHOWED THE ASYMMETRIC NATURE OF THE WIND FIELD, WITH THE
PREPONDERANCE OF THE GALE FORCE OR HIGHER WINDS LIMITED TO THE
SOUTHERN HEMISPHERE OF THE SYSTEM, WITH A SMALL REGION OF
GALE-FORCE WINDS TO THE NORTHWEST OF THE ELONGATED AND DISORGANIZED
LLCC. THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE BASED
ON AN EXTRAPOLATION OF THE SAR-BASED CENTER AND NEAR THE PGTW AND
FMEE FIX POSITIONS. THE INITIAL INTENSITY IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE SAR DATA, WHICH INDICATED WINDS UP TO 44
KNOTS ROUGHLY 15NM TO THE SOUTH OF THE LLCC. SURFACE OBSERVATIONS
SAINTE MARIE AERODROME SHOW INCREASING SOUTHWESTERLY WINDS, HOWEVER
SURFACE PRESSURES REMAIN HIGH (1009 MB), WHICH INDICATES THE VERY
SMALL NATURE OF THE CORE OF THE SYSTEM. CONVECTION IS ERODING ON
THE NORTHEASTERN PERIPHERY AS LOW LEVEL DRY AIR ENTRAINMENT AND
DOWNWARD VERTICAL MOTION MOVE OFFSHORE NORTHERN MADAGASCAR AND WRAP
INTO THE CORE.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE SOUTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   FMEE: T2.5 - 35 KTS
   CIMSS SATCON: 52 KTS AT 150307Z
   CIMSS ADT: 51 KTS AT 150315Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 12S WILL CONTINUE TRACKING WESTWARD ALONG
THE NORTHERN PERIPHERY OF THE STR THROUGH THE FORECAST PERIOD. THE
SYSTEM IS EXPECTED TO MAKE LANDFALL AT NOSY BORAHA ISLAND WITHIN
THE NEXT FEW HOURS THEN TRACK INLAND ACROSS THE NORTHERN PORTION OF
MADAGASCAR. DUE TO THE SHORT TIME REMAINING BEFORE LANDFALL AND THE
OVERALL MARGINAL ENVIRONMENTAL CONDITIONS, LITTLE TO NO
INTENSIFICATION IS EXPECTED PRIOR TO THE SYSTEM MOVING OVER LAND.
ONCE ASHORE THE SYSTEM WILL GRADUALLY BUT STEADILY WEAKEN AS IT
MOVES OVER THE MOUNTAINOUS TERRAIN AND ULTIMATELY DISSIPATE BELOW
WARNING THRESHOLD PRIOR TO REACHING THE WEST COAST OF MADAGASCAR.
THE REMNANT CIRCULATION IS EXPECTED TO MOVE OUT OVER THE NORTHERN
MOZAMBIQUE CHANNEL AROUND TAU 36. WHILE THE SSTS ARE VERY WARM IN
THE CHANNEL, THE PRESENCE OF MID-LEVEL DRY AIR AND MODERATE TO HIGH
EASTERLY SHEAR WILL PRECLUDE REDEVELOPMENT.  

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN VERY GOOD
AGREEMENT, WITH MINIMAL SPREAD IN THE MODEL TRACKERS, THROUGH THE
FORECAST PERIOD, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST
TRACK. INTENSITY GUIDANCE IS FOR THE MOST PART IN AGREEMENT. WITH
THE EXCEPTION OF THE NAVGEM DECAY SHIPS, ALL AVAILABLE GUIDANCE
INDICATES RAPID WEAKENING OVER LAND TO 25-30 KNOTS, AND REMNANT
CIRCULATION HOLDING ON AT 30 KNOTS AS IT CROSSES THE CHANNEL.  

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