WDXS31 PGTW 010300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04S (ALVARO) WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.7S 40.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 96 NM NORTH-NORTHEAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: EASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM
HAS OVERALL MAINTAINED ITS CORE CONVECTION EVEN AS THE CONVECTIVE
BANDS FROM NORTH TO EAST HAVE EXPANDED. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE MICROWAVE LOW LEVEL 
CIRCULATION (LLC) FEATURE IN THE 312216Z AMSR2 IMAGE AND 
EXTRAPOLATION OF LOW CLOUD LINES FEEDING INTO A PARTLY EXPOSED LLC IN 
THE EIR LOOP. THE INITIAL INTENSITY IS PLACED WITH MEDIUM CONFIDENCE 
BASED ON RECENT SCATTEROMETER DATA AND SUPPORTED BY THE PGTW DVORAK 
ESTIMATE OF T2.5. ANALYSIS INDICATES A MARGINALLY FAVORABLE 
ENVIRONMENT WITH WARM SST AND STRONG POLEWARD OUTFLOW OFFSET BY 
MODERATE VERTICAL WIND SHEAR (VWS) AND DRY AIR ENTRAINMENT FROM THE 
SOUTHWEST.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA.

CURRENT STEERING MECHANISM: NEAR EQUATORIAL RIDGE (NER) TO THE
NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 37 KTS AT 312100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC ALVARO WILL TRACK MORE EAST-SOUTHEASTWARD,
MAKE LANDFALL ALONG THE SOUTHWEST COAST OF MADAGASCAR AROUND TAU 18, 
DRAG ACROSS THE RUGGED TERRAIN THEN EXIT INTO THE SOUTH INDIAN OCEAN 
AFTER TAU 48. THE MARGINALLY FAVORABLE ENVIRONMENT WILL, AT BEST, 
MAINTAIN ITS CURRENT INTENSITY. AFTERWARD, LAND INTERACTION, 
INCREASING VWS AND DRY AIR ENTRAINMENT WILL ERODE AND DISSIPATE THE
SYSTEM BY TAU 24. HOWEVER, AFTER IT EXITS BACK OVER WATER, INCREASED 
MOISTURE AND POLEWARD OUTFLOW WILL REVIVE THE SYSTEM BACK TO 35KTS. 
BY TAU 96, EXTREMELY HIGH VWS, COOLING SST, AND INTERACTION WITH THE 
SUBTROPICAL ENVIRONMENT WILL ONCE AGAIN DISSIPATE THE SYSTEM. THERE 
IS A DISTINCT POSSIBILITY THAT TC 04S WILL NOT RECOVER FROM 
DISSIPATION OVER MADAGASCAR.   

MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL GOOD AGREEMENT
SPREADING OUT TO 310NM BY TAU 96. HOWEVER, GIVEN THE UNCERTAINTY OF
TRACKING OVER RUGGED TERRAIN, THERE IS OVERALL LOW CONFIDENCE IN
THE JTWC TRACK AND INTENSITY FORECASTS.  

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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