WDXS31 PGTW 021500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (ELEVEN) WARNING 
NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.3S 55.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 77 NM NORTH-NORTHEAST OF ST DENIS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 11S WITH CENTRAL CONVECTION BUILDING OVER THE CENTER OF THE
OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC). ENVIRONMENTAL
ANALYSIS INDICATES THAT 11S IS IN A MARGINALLY FAVORABLE
ENVIRONMENT CHARACTERIZED BY MODERATE EQUATORWARD OUTFLOW ALOFT,
LOW (10-15 KTS) VERTICAL WIND SHEAR, AND WARM (28-29 C) SEA SURFACE
TEMPERATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE
BASED ON LOW-LEVEL CLOUD TRACING IN THE ANIMATED MSI. THE INITIAL
INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
AGENCY DVORAK AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: NORTHEASTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) POSITIONED TO THE SOUTHWEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   FMEE: T2.5 - 35 KTS
   CIMSS ADT: 34 KTS AT 021200Z
   CIMSS AIDT: 35 KTS AT 021200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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: 11S IS FORECAST IS TO TRACK GENERALLY WESTWARD
THROUGH TAU 24. AROUND TAU 24, THE RIDGE WILL CONTINUE TO BUILD,
WHICH WILL PUSH THE SYSTEM TO THE NORTHWEST THROUGH TAU 48. JUST
BEFORE TAU 48, 11S IS FORECAST TO MAKE LANDFALL, NEAR TOAMASINA.
AFTER TAU 48, THE SYSTEM WILL THEN TRACK FURTHER WESTWARD, ACROSS
THE RUGGED TERRAIN OF CENTRAL MADAGASCAR. NEAR TAU 84, 11S WILL
ENTER THE MOZAMBIQUE CHANNEL AND CONTINUE ITS WESTWARD TRACK
THROUGH THE REMAINDER OF THE FORECAST PERIOD. REGARDING INTENSITY,
11S IS FORECAST TO STEADILY INTENSIFY THROUGH TAU 36, TO AROUND 50
KTS, DUE TO THE LESSENED VERTICAL WIND SHEAR. AFTER MAKING
LANDFALL, TERRAIN INTERACTION WILL CAUSE 11S TO WEAKEN AS IT
CROSSES MADAGASCAR. ONCE WITHIN THE MOZAMBIQUE CHANNEL,
ENVIRONMENTAL CONDITIONS WILL GREATLY IMPROVE WITH VERY WARM SEA
SURFACE TEMPERATURES AND LOW VERTICAL WIND SHEAR. THIS WILL ALLOW
11S TO REINTENSIFY TO AROUND 45 KTS AT TAU 120. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE TRACK OF 11S THROUGH TAU 48. AFTER TAU 48, LAND
INTERACTION CAUSES THE MODELS TO DIVERGE. GALWEM AND UKMET TRACKS
THE SYSTEM SHARPLY TO THE SOUTHWEST AFTER MAKING LANDFALL WHILE THE
REMAINDER OF GUIDANCE HAS THE SYSTEM TRACK NEARLY STRAIGHT
WESTWARD. THE JTWC TRACK FORECAST IS PLACED CLOSER TO THE MAIN
GROUPING OF GUIDANCE WITH MEDIUM CONFIDENCE THROUGH TAU 72 AND LOW
CONFIDENCE THEREAFTER. INTENSITY GUIDANCE IS ALL OVER THE PLACE DUE
TO THE TIMING OF LANDFALL AND TIME OVER LAND. HOWEVER, THE OVERALL
TREND IS SIMILAR, WITH WEAKENING OVER LAND AND REINTENSIFICATION
WITHIN THE CHANNEL. THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO
CONSENSUS WITH OVERALL LOW CONFIDENCE. 

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