WDXS32 PGTW 280300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 09S (GRANT) WARNING NR 
022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.3S 86.7E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 896 NM EAST-SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 09S (GRANT) WITH A HIGHLY COMPACT CENTRAL DENSE OVERCAST
(CDO) OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). CLOUD TOPS
WITHIN THE CORE OF THE SYSTEM ARE NOW MEASURING COLDER THAN -90 C
IN SOME AREAS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE ANIMATED EIR IMAGERY. THE INITIAL INTENSITY OF 65 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES
ALL AGREEING ON T4.0. ADDITIONALLY, THE CIMSS OBJECTIVE ESTIMATES
RANGING FROM 59-72 KTS FURTHER SUPPORT THE INITIAL INTENSITY
ASSESSMENT. ENVIRONMENTAL ANALYSIS INDICATES THAT 09S IS IN A
MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE POLEWARD
OUTFLOW ALOFT, LOW (10-15 KTS) EASTERLY VERTICAL WIND SHEAR, AND
WARM (27-28 C) SEA SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: PERSISTENCE FROM THE 1607Z METOP-C ASCAT
PASS WITH SLIGHT ADJUSTMENTS BASED ON THE OBJECTIVE BEST TRACK.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) POSITIONED TO
THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   DEMS: T4.0 - 65 KTS
   FMEE: T4.0 - 65 KTS
   FIMP: T4.0 - 65 KTS
   CIMSS SATCON: 59 KTS AT 272215Z
   CIMSS ADT: 72 KTS AT 280015Z
   CIMSS AIDT: 68 KTS AT 280015Z
   CIMSS D-PRINT: 59 KTS AT 280015Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE 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 09S IS FORECAST TO TRACK
WEST-SOUTHWESTWARD, ALONG THE NORTHERN PERIPHERY OF THE STR TO THE
SOUTH THROUGH TAU 48. NEAR TAU 48, A SECOND STR IS EXPECTED TO
BUILD TO THE SOUTHWEST OF 09S AND PROPAGATE EASTWARD, KEEPING THE
TRAJECTORY FIRMLY WEST-SOUTHWESTWARD THROUGH TAU 96. NEAR TAU 96,
09S IS FORECAST TO BEGIN INTERACTING WITH RIDGING THAT EXTENDS FROM
EASTERN AFRICA OVER NORTHERN MADAGASCAR, CAUSING THE TRACK TO SHIFT
WEST-NORTHWESTWARD NEAR THE END OF THE FORECAST PERIOD. REGARDING
INTENSITY, 09S IS FORECAST TO INTENSIFY OVER THE NEXT 36-48 HOURS
AS EASTERLY SHEAR LESSENS AND POLEWARD OUTFLOW BECOMES ENHANCED BY
A PASSING UPPER-LEVEL TROUGH TO THE SOUTH. AFTER TAU 48, SHEAR IS
EXPECTED TO INCREASE AND OUTFLOW DECREASE CAUSING THE SYSTEM TO
BEGIN WEAKENING. ADDITIONALLY, DRY AIR ENTRAINMENT FROM THE NORTH
WILL FURTHER AID IN WEAKENING THE SYSTEM THROUGH THE REMAINDER OF
THE FORECAST PERIOD. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE REMAINS IN GOOD
AGREEMENT WITH NO NOTABLE OUTLIERS. THE JTWC TRACK FORECAST IS
PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE.
INTENSITY GUIDANCE IS SPLIT WITH GFS AND COAMPS-TC CALLING FOR A
STEADY INTENSITY THROUGH TAU 96 WHILE HAFS-A AND HWRF CALL FOR
INTENSIFICATION THROUGH TAU 48 BEFORE STEADY WEAKENING. HAFS-A
CONTINUES TO BE THE MOST AGGRESSIVE MODEL SHOWING A PEAK INTENSITY OF
AROUND 110 KTS AT TAU 48. THE JTWC INTENSITY FORECAST IS PLACED
NEAR THE CONSENSUS, AND IN LINE WITH THE PREVIOUS FORECAST, WITH
OVERALL MEDIUM CONFIDENCE.

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