WDXS31 PGTW 092100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 07S (DIKELEDI) WARNING 
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.6S 60.1E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 422 NM NORTH-NORTHEAST OF PORT LOUIS,
MAURITIUS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 07S WITH PERSISTENT CONVECTION OVER THE OBSCURED LOW-LEVEL
CIRCULATION CENTER (LLCC). STRONG WESTWARD AND POLEWARD OUTFLOW IS
APPARENT WITH THE PRESENCE OF WELL-DEFINED CIRRUS FILAMENTS
EXPANDING OUTWARD IN THOSE DIRECTIONS. ENVIRONMENTAL ANALYSIS
INDICATES THAT 07S IS IN A FAVORABLE ENVIRONMENT FOR DEVELOPMENT
CHARACTERIZED BY THE ROBUST 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 THE
ANIMATED EIR. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES LISTED BELOW.
ADDITIONALLY, A 091137Z CIMSS DMINT ESTIMATE WAS 42 KTS.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   FMEE: T3.5 - 55 KTS
   FIMP: T3.5 - 55 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: 07S IS FORECAST TO CONTINUE TRACKING
WEST-NORTHWESTWARD ALONG THE NORTHERN PERIPHERY OF THE STR TO THE
SOUTH THROUGH TAU 48. LANDFALL IS FORECAST TO OCCUR AROUND TAU 48
ALONG THE NORTHERN TIP OF MADAGASCAR. AFTER TAU 48, THE SYSTEM IS
EXPECTED TO MAKE A SOUTHWESTWARD TURN AS IT ROUNDS THE RIDGE AXIS.
AROUND TAU 96, 07S WILL BEGIN TO TRACK MORE SOUTHWARD THROUGH THE
MOZAMBIQUE CHANNEL AS IT RUNS ALONG THE WESTERN PERIPHERY OF THE
STR. REGARDING INTENSITY, 07S IS FORECAST TO STEADILY INTENSIFY
OVER THE NEXT 36 HOURS TO A PEAK OF AROUND 70 KTS AS THE
ENVIRONMENT REMAINS CONDUCIVE. NEAR TAU 48, 07S WILL MAKE LANDFALL
AND BEGIN TO WEAKEN. THE AMOUNT OF WEAKENING WILL DEPEND HIGHLY ON
THE AMOUNT OF TERRAIN INTERACTION WITH NORTHERN MADAGASCAR. IF IT
MAKES LANDFALL FURTHER SOUTH, THEN IT COULD WEAKEN MUCH MORE THAN
CURRENTLY FORECAST. AS IT STANDS, 07S WILL BRUSH THE NORTHERN TIP
AND THEN WEAKN TO AROUND 60 KTS. IT WILL MAINTIAN INTENSITY THROUGH
TAU 120 AS INCREASED SHEAR (20-25 KTS) FIGHTS THE WARM (30 C) SEA
SURFACE TEMPERTAURES WITHIN THE MOZAMBIQUE CHANNEL. IN THE EXTENDED
FORECAST (PAST TAU 120), FURTHER INTENSIFICATION IS PROBABLE AS THE
POLEWARD OUTFLOW CHANNEL WILL GREATLY IMPROVE. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE TRACK OF 07S THROUGH TAU 48. AFTER TAU 48, MODELS
DIVERGE DUE TO THE SHARPNESS OF THE TURN AROUND THE STR. GFS TAKES
A WIDER TURN, CLOSER TO MOZAMBIQUE, WHILE ECMWF TAKES A SHARPER
TURN, CLOSER TO THE WESTERN COAST OF MADAGASCAR. INTENSITY GUIDANCE
IS IN WORSE AGREEMENT. RAPID INTENSIFICATION (RI) PROBABILITIES
OVER THE NEXT 36 ARE HOVERING AROUND 20 PERCENT, SO IT SHOULD NOT
BE OUT OF THE QUESTION. THE JTWC INTENSITY FORECAST IS PLACED WITH
OVERALL LOW CONFIDENCE DUE TO THE RI CHANCE AND THEN THE VARIANCE
REGARDING THE AMOUNT OF LAND INTERACTION WITH NORTHERN MADAGASCAR.

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