WDXS32 PGTW 301500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 09S (GRANT) WARNING NR 
027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.7S 75.6E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 491 NM SOUTH-SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 33 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 09S (GRANT) HAS RETAINED ITS COMPACT
STRUCTURE AS THE SYSTEM CONTINUES TO TRACK WEST-SOUTHWESTWARD WITH
SPIRALING BANDS OF DEEP CONVECTION SURROUNDING THE EYE FEATURE AS
DEPICTED VIA ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY.
LITTLE CHANGE IN THE STRUCTURE OF THE TC HAS BEEN OBSERVED AS CLOUD
TEMPERATURES HAVE REMAINED CLOSE TO -90 C. THE EYE HAS BEEN
VISIBLY TILTED AT TIMES AND BECAME CLOUD FILLED ONLY TO CLEAR AGAIN
AND ALIGN BETTER LATER. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE EVIDENT EYE FEATURE SEEN ON EIR IMAGERY.
THE INITIAL INTENSITY OF 120 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON OBJECTIVE ESTIMATES AND AGENCY FIXES WITH NO NEW WIND 
SCATTEROMETRY OR SAR DATA SINCE THE 300013Z RCM-2 SAR PASS.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE SOUTH 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   DEMS: T6.0 - 115 KTS
   FMEE: T6.0 - 115 KTS
   FIMP: T6.0 - 115 KTS
   CIMSS SATCON: 103 KTS AT 301030Z
   CIMSS ADT: 109 KTS AT 301230Z
   CIMSS AIDT: 105 KTS AT 301230Z
   CIMSS D-MINT: 96 KTS AT 301119Z
   CIMSS D-PRINT: 95 KTS AT 301230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG RADIAL

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 09S IS FORECASTED TO CONTINUE WEST-
SOUTHWESTWARD UNTIL AFTER TAU 48 UNDER THE INFLUENCE OF THE
SUBTROPICAL RIDGE TO THE SOUTH. AFTERWARDS, A BUILDING SUBTROPICAL 
RIDGE OVER MADAGASCAR WILL CAUSE THE SYSTEM TO SHIFT NORTHWESTWARD 
UNTIL TAU 96 WHEN THE INFLUENCE OF THE RIDGE BEGINS TO WANE. A 
WEAKENING TREND IS FORECASTED UNTIL TAU 96 AS THE SYSTEM IS NOW 
BATTLING THE SURROUNDING DRY AIR AND AN INCREASE IN VERTICAL WIND 
SHEAR. AFTER TAU 96 THE SECOND RIDGE WILL BE ABLE TO STEER THE
SYSTEM INTO A MORE FAVORABLE ENVIRONMENT WITH DECREASED VERTICAL
WIND SHEAR AND INCREASED AVAILABLE MOISTURE, AS SUCH THE END OF THE
FORECAST REFLECTS POTENTIAL FOR SLIGHT INTENSIFICATION.

MODEL DISCUSSION: CROSS TRACK SPREAD AMONGST MODEL GUIDANCE IS
UNDER 100 NM UNTIL TAU 48. AFTER TAU 48 NAVGEM FORECASTS A
SIGNIFICANTLY MORE NORTHWARD TRACK APPARENTLY DISREGARDING THE
HANDOFF OF THE STEERING BETWEEN THE TWO SUBTROPICAL RIDGES. THE JTWC
FORECASTED TRACK IS PLACED SLIGHTLY SOUTH OF THE MULTI MODEL
CONSENSUS WITH MEDIUM CONFIDENCE AFTER TAU 72 ACCOUNTING FOR THE
MORE SOUTHERN TRACK PREFERRED BY THE MAJORITY OF THE MODEL GUIDANCE 
ENVELOPE. INTENSITY GUIDANCE IS SPREAD UP TO 45 KTS AT TAU 48 AND 
CONTINUES TO SPREAD AFTERWARDS. THE MAJORITY OF THE MODELS REFLECT A 
STEADY WEAKENING TREND UNTIL TAU 72. COAMPS-TC DISAGREES DEPICTING A 
STRENGTHENING TREND AFTER TAU 36. THE JTWC FORECASTED INTENSITY 
REFLECTS VALUES IN LINE WITH THE MULTI MODEL CONSENSUS WITH MEDIUM 
CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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