WDXS31 PGTW 060300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 08S (BATSIRAI) 
WARNING NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.3S 46.9E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 148 NM SOUTH-SOUTHWEST OF ANTANANARIVO,
MADAGASCAR
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 0 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TC 08S MADE LANDFALL ALONG THE COAST OF MADAGASCAR, JUST NORTH OF
THE TOWN OF MANANJARY, AROUND 051700Z. AS THE SYSTEM WAS MAKING
LANDFALL, THE EYE SHRUNK DOWN FROM 25-NM TO LESS THAN 12-NM, WHILE
CLOUD TOP TEMPERATURES FELL TO -80C OR COLDER AND THE LAST
OBSERVATION FROM MANANJARY AT 051500Z INDICATED SUSTAINED 10-MIN
WINDS OF 90 KNOTS. HENCE, THE 051800Z INTENSITY WAS HELD AT 100
KNOTS THROUGH THE LANDFALL EVENT. SUBSEQUENTLY THE SYSTEM HAS MOVED
OVER THE RUGGED TERRAIN OF SOUTH-CENTRAL MADAGASCAR AND BEGUN TO
RAPIDLY WEAKEN. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY
DEPICTS A RAPIDLY ERODING STRUCTURE, WITH DRAMATICALLY WARMER CLOUD
TOP TEMPERATURES AND WEAK, FRAGMENTED BANDING. THE LACK OF RECENT
MICROWAVE IMAGERY, SURFACE OBSERVATIONS OR RADAR DATA LEND ONLY LOW
CONFIDENCE TO THE INITIAL POSITION. WITH THE POSITION OVER LAND,
THERE ARE NO DVORAK-BASED INTENSITY ESTIMATES AND NEARBY SURFACE
OBSERVATION POINTS ARE NOT REPORTING AT THIS TIME, THEREFORE THE
INITIAL INTENSITY IS BASED STRICTLY OFF EXPECTED OR MODELED
WEAKENING OVER COMPLEX TERRAIN, WITH LOW CONFIDENCE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHWEST PERIPHERY OF DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 0-5 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: DRY AIR OVER LAND AND TERRAIN INFLUENCES

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: LOW
   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 08S IS BEING STEERED TO THE WEST-SOUTHWEST
ALONG THE NORTHWESTERN PERIPHERY OF A DEEP STR TO THE SOUTH, AT A
SPEED OF ROUGHLY 12 KNOTS. SOME ADDITIONAL SLOWING CAN BE EXPECTED
IN THE NEAR-TERM, BUT ONCE THE SYSTEM CROSSES THE RIDGE OF THE
MOUNTAIN RANGE, IT WILL LIKELY PICK UP SPEED AS IT TRACKS TOWARDS
THE WEST COAST OF MADAGASCAR. AS THE SYSTEM CROSSES THE ISLAND, LOW
LEVEL FLOW DISRUPTION AND FRICTIONAL EFFECTS WILL LEAD TO CONTINUED
WEAKENING. TC 08S IS EXPECTED TO REEMERGE INTO THE MOZAMBIQUE
CHANNEL WITHIN THE NEXT 18-24 HOURS AT A GREATLY REDUCED INTENSITY
OF NEAR 40 KNOTS. THE SYSTEM IS EXPECTED TO REACH THE AXIS OF THE
STEERING RIDGE BY TAU 36 AND SLOW DOWN UNDER A WEAKENED STEERING
FLOW, THEN ACCELERATE POLEWARD AFTER TAU 48 AS IT ROUNDS THE RIDGE
AXIS. CONDITIONS WILL BE MARGINALLY FAVORABLE AS THE SYSTEM MOVES
INTO THE CHANNEL, WITH WARM (27-28C) WATERS AND ENHANCED POLEWARD
OUTFLOW OFFSETTING MODERATE SHEAR FOR ABOUT 24 HOURS, ALLOWING FOR
AN INTENSIFICATION TO 50 KNOTS. INCREASING SHEAR AND DRY AIR WILL
BEGIN TO OVERWHELM TO EFFECT OF THE ENHANCED OUTFLOW AFTER TAU 48,
LEADING TO A STEADY WEAKENING TREND THROUGH THE REMAINDER OF THE
FORECAST PERIOD. TC 08S WILL BEGIN SUBTROPICAL TRANSITION BY TAU 72
AS IT CROSSES THE 26C ISOTHERM AND BEGINS TO MOVE UNDER A MID-LEVEL
LOW. SUBTROPICAL TRANSITION IS EXPECTED BY TAU 96 AS SSTS DROP
BELOW 24C AND THE SYSTEM BECOMES EMBEDDED IN THE UPPER-LEVEL
WESTERLY FLOW. 

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT ON THE
OVERALL SCENARIO, AND EXHIBITS A 135NM SPREAD AT TAU 72, INCREASING
TO 150NM AT TAU 96. WHILE CROSS-TRACK SPREAD IS MINIMAL,
ALONG-TRACK SPREAD INCREASES SIGNIFICANTLY AFTER TAU 72, UP TO
600NM BETWEEN OUTLIERS. THE JTWC FORECAST LIES ON THE RIGHT SIDE OF
THE GUIDANCE PACKAGE THROUGH TAU 24, THEN JUST WEST OF THE
CONSENSUS MEAN THROUGH TAU 72 WITH HIGH CONFIDENCE. THE INCREASED
ALONG-TRACK SPREAD AFTER TAU 72 LENDS MEDIUM CONFIDENCE TO THAT
PORTION OF THE TRACK FORECAST. INTENSITY GUIDANCE IS IN STRONG
AGREEMENT WITH THE SYSTEM EMERGING INTO THE CHANNEL AT 40 KNOTS,
FOLLOWED BY A REINTENSIFICATION TO A PEAK BETWEEN 45-55 KTS. THE
JTWC FORECAST LIES CLOSE TO THE CONSENSUS MEAN IN THE EARLY TAUS,
THEN JUST BELOW THE HWRF PEAK THROUGH THE REMAINDER OF THE
FORECAST.

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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