WDXS31 PGTW 280300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 20S (GAMANE) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.9S 48.8E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 309 NM NORTH-NORTHEAST OF ANTANANARIVO,
MADAGASCAR
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 0 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM
CONTINUED TO UNRAVEL AND ITS DEEP CENTRAL AND FEEDER BAND
CONVECTION DISORGANIZE AS IT TRACKED DEEPER INLAND OVER THE RUGGED
TERRAIN OF NORTHERN MADAGASCAR. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE USING LOW CLOUD TRACING INTO AN OBSCURED LOW
LEVEL CIRCULATION (LLC) AND EXTRAPOLATION FROM A MICROWAVE LLC IN THE
272222Z ASMR2 36GHZ IMAGE. THE INITIAL INTENSITY IS ESTIMATED WITH 
MEDIUM CONFIDENCE BASED ON THE RATE OF DECAY OVER LAND. ANALYSIS 
INDICATES AN UNFAVORABLE ENVIRONMENT MOSTLY DUE TO FRICTIONAL EFFECTS 
FROM THE LAND INTERACTION.

INITIAL WIND RADII BASIS: PROPORTIONALLY ADJUSTED FROM LAST KNOWN
SCATTEROMETER COVERAGE. 

CURRENT STEERING MECHANISM: SOUTHWEST PERIPHERY OF SUBTROPICAL
RIDGE TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 5-10 KTS
   SST: OVER LAND
   OUTFLOW: STRONG POLEWARD

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 GAMANE HAS CRESTED THE STR AXIS AND WILL
TRACK SOUTHEASTWARD, EXIT BACK INTO THE SOUTH INDIAN OCEAN (SIO)
JUST BEFORE TAU 36, THEN ACCELERATE TOWARD MAURITIUS. BY TAU 72, IT
WILL APPROACH THE BAROCLINIC ZONE UNDERNEATH THE JET STREAM
ASSOCIATED WITH THE PREVAILING WESTERLIES AND BEGIN SUBTROPICAL
TRANSITION. BY TAU 96, TC 20S WILL TRANSFORM INTO A SUBTROPICAL
SYSTEM WITH AN EXPANDING WIND FIELD AS IT MAKES LANDFALL OVER
MAURITIUS. THE JTWC BEST TRACK CONTINUED TO FISH-BONE WESTWARD
RESULTING IN A MORE PROLONGED TRACK OVER LAND. IF THIS TREND
CONTINUES, THERE IS A DISTINCT POSSIBILITY THAT TC GAMANE MAY
DISSIPATE BEFORE IT REACHES THE SIO.    

MODEL DISCUSSION: NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT
WITH THE NOTABLE EXCEPTION OF AFUM THAT KEEPS THE VORTEX IN A
QUASI-STATIONARY STATE OVER THE NORTHWEST COAST OF MADAGASCAR. SANS
AFUM, THE MODEL ENVELOPE SPREADS OUT TO A MERE 102NM ACROSS TRACK
BY TAU 96 BUT WITH VARYING ALONG-TRACK SPEEDS WITH GFS LEADING THE
PACK. IN VIEW OF THESE, THERE IS ONLY MEDIUM CONFIDENCE IN THE JTWC
TRACK FORECAST THAT IS LAID SLIGHTLY TO THE LEFT OF AND FASTER THAN
CONSENSUS TO OFFSET AFUM. THE INTENSITY FORECAST CONFIDENCE IS LOW
DUE TO THE UNCERTAINTIES WITH THE TRACK OVER LAND THAT MAY RESULT
IN EARLY DISSIPATION.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
NNNN