WDXS31 PGTW 041500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11S (FAIDA) WARNING NR 
016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.6S 50.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 170 NM EAST-SOUTHEAST OF ANTANANARIVO,
MADAGASCAR
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) MOVING SOUTHWARD ALONG
THE EAST COAST OF MADAGASCAR. THIS ROTATION WAS FIRST SEEN OVER 12
HOURS AGO BUT WAS NOT THOUGHT TO BE THE ACTUAL CENTER OF THE SYSTEM
AT THAT TIME. SUBSEQUENT ANALYSIS HAS DETERMINED THAT THIS IS THE
PRIME SUSPECT IN BEING THE TRUE CENTER OF CIRCULATION OF THE
REMNANTS OF TC 11S. THE LLCC HAS BEEN RELOCATED OVER 90NM SOUTHEAST
OF THE PREVIOUS BEST TRACK POSITION, AND THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC IN THE MSI.
THE INITIAL INTENSITY IS ASSESSED WITH LOW CONFIDENCE, HEDGED ABOVE
THE LIMITED INTENSITY ESTIMATES NOTED ABOVE BASED ON PERSISTENCE.
ANALYSIS REVEALS AN UNFAVORABLE ENVIRONMENT, WITH MODERATE
SOUTHEASTERLY SHEAR, WEAK OUTFLOW ALOFT AND WARM SSTS. DRY
MID-LEVEL AIR IS ENGULFING THE SYSTEM AND KEEPING A SOLID LID ON
CONVECTIVE DEVELOPMENT.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   CIMSS D-MINT: 31 KTS AT 041221Z
   CIMSS D-PRINT: 28 KTS AT 041230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: VERY DRY MID-LEVEL AIR. 

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE SYSTEM HAS BEEN RELOCATED AND THE
FORECAST TRACK HAS SHIFTED SIGNIFICANTLY SOUTHWARD, NOW EXPECTED TO
CROSS MADAGASCAR FURTHER SOUTH THAN ANTICIPATED. THE INTENSITY
FORECAST HAS ALSO BEEN LOWERED SIGNIFICANTLY. 

FORECAST DISCUSSION: THE RELOCATION OF TC 11S HAS RESULTED IN A
SIGNIFICANT CHANGE IN THE FORECAST PHILOSOPHY. THE SYSTEM IS
RELATIVELY SHALLOW AND THUS BEING STEERED BY THE LOW- TO MID-LEVELS
OF THE STR TO THE EAST, WHICH ARE ORIENTED ROUGHLY NORTH TO SOUTH.
THE ORIENTATION OF THE RIDGING SHIFTS SUBTLY AFTER TAU 12, TO A
MORE NORTHEAST-SOUTHWEST AXIS, AND THE REMNANTS OF TC 11S ARE
EXPECTED TO TURN SOUTHWESTWARD, MAKING LANDFALL ALONG THE EAST
COAST OF MADAGASCAR AROUND TAU 18. THE SYSTEM WILL WEAKEN RAPIDLY
PRIOR TO LANDFALL AND CONTINUE WEAKENING THEREAFTER, WITH THE
REMNANT VORTEX QUICKLY CROSSING THE MOUNTAINS AND REEMERGING IN THE
MOZAMBIQUE CHANNEL BY TAU 48. ONCE THE SYSTEM MOVES BACK INTO OPEN
WATERS, IT WILL MOVE WESTWARD ALONG THE NORTH SIDE OF A STR
CENTERED NEAR THE SOUTHERN TIP OF MADAGASCAR. CONDITIONS GENERALLY
BECOME MORE FAVORABLE CONDITIONS, WITH VERY WARM SSTS, RELATIVELY
LOW SHEAR AND INCREASED MOISTURE IN THE MID-LEVELS, THOUGH OUTFLOW
WILL REMAIN CONSTRAINED AND LIMITED. THUS, ONLY A SMALL AMOUNT OF
REINTENSIFICATION IS EXPECTED AT THIS TIME. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS A HOT MESS, WITH
MOST OF THE MODELS LOSING THE VORTEX ENTIRELY AFTER ABOUT TAU 48 OR
MOVING IT IN AN ERRATIC FASHION. THROUGH TAU 48, THE JTWC TRACK 
GENERALLY FOLLOWS THE CONSENSUS MEAN, THEN REJOINS THE PREVIOUS
JTWC FORECAST TRACK AND THE HAFS-A TRACKER THROUGH THE REMAINDER OF
THE FORECAST PERIOD. CONFIDENCE IS EXTREMELY LOW THROUGHOUT THE
FORECAST. INTENSITY GUIDANCE IS HOWEVER IN MUCH BETTER AGREEMENT,
WITH THE LIMITED GUIDANCE AVAILABLE SUPPORTING A NEAR-TERM
WEAKENING AS THE SYSTEM CROSSES MADAGASCAR, FOLLOWED BY A
REINTENSIFICATION AFTER TAU 48. THE HAFS-A IS THE MOST AGGRESSIVE
IN SHOWING A PEAK AROUND 45 KNOTS IN THE CHANNEL, WHILE THE JTWC
FORECAST IS SITUATED ABOUT 10 KNOTS WEAKER. SIMILAR TO THE TRACK
FORECAST, THE LACK OF A FULL SUITE OF GUIDANCE AND THE FACT THAT
MULTIPLE MODELS LOSE THE VORTEX ALL TOGETHER AFTER LANDFALL, MAKES
FOR A VERY LOW CONFIDENCE FORECAST. 

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