WDXS32 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 09S (GRANT) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.1S 98.2E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 76 NM EAST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 09S (GRANT) WITH SIGNIFICANTLY IMPROVED CENTRAL CONVECTION
AND AN APPARENT DROP IN VERTICAL WIND SHEAR OVER THE PAST 6 HOURS.
CLOUD ELEMENTS WITHIN THE EASTERN PORTION OF THE CIRCULATION ARE NO
LONGER BEING PRESSED INWARD AND OUTFLOW APPEARS TO BE LESS
RESTRICTED. HOWEVER, DRIER AIR CONTINUES TO BE PULLED INTO THE
VORTEX FROM THE WEST AND NORTH. A 232330Z SSMIS 91 GHZ MICROWAVE
IMAGE REVEALED TWO DISTINCT LOBES OF DEEP CONVECTION WITHIN THE
EASTERN AND WESTERN SEMICIRCLES OF THE CIRCULATION AND DEFINED
LOW-LEVEL CLOUD LINES WRAPPING INTO THE CENTER. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE COMBINATION
OF ANIMATED MSI AND THE SSMIS MICROWAVE IMAGE. THE INITIAL
INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
AGENCY DVORAK AND CIMSS OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.
ENVIRONMENTAL ANALYSIS INDICATES THAT 09S IS IN A MARGINALLY
FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE POLEWARD OUTFLOW,
LOW (10-15 KTS) NORTHEASTERLY VERTICAL WIND SHEAR, SLIGHT DRY AIR
ENTRAINMENT, AND WARM (27-28 C) SEA SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: PERSISTENCE WITH SLIGHT ADJUSTMENTS BASED
ON THE OBJECTIVE BEST TRACK

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   DEMS: T3.0 - 45 KTS
   APRF: T2.5 - 35 KTS
   CIMSS SATCON: 38 KTS AT 240030Z
   CIMSS ADT: 39 KTS AT 240030Z
   CIMSS AIDT: 31 KTS AT 240030Z
   CIMSS D-MINT: 35 KTS AT 232314Z
   CIMSS D-PRINT: 32 KTS AT 240030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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: TC 09S IS FORECAST TO TRACK NORTHWESTWARD FOR
ONLY ANOTHER 12 HOURS BEFORE THE TRACK FLATTENS TO A MORE WESTWARD
TRAJECTORY AS THE SYSTEM TRACKS ALONG THE NORTHERN PERIPHERY OF
RIDGING TO BOTH THE SOUTHEAST AND SOUTHWEST. THE WESTWARD MOVEMENT
WILL PERSIST THROUGH AROUND TAU 60. NEAR TAU 60, THE STR TO THE
SOUTHEAST OF 09S IS EXPECTED TO BUILD AND MERGE WITH THE STR THAT
IS TO THE SOUTHWEST. AFTER THE TWO RIDGES MERGE, THE RESULTING
RIDGING COMPLEX WILL BE ORIENTED IN A NORTHEAST-SOUTHWEST
ORIENTATION. AS A RESULT, 09S IS FORECAST TO TRACK
WEST-SOUTHWESTWARD WITH INCREASING TRACK SPEEDS THROUGH THE
REMAINDER OF THE FORECAST PERIOD. REGARDING INTENSITY, 09S IS
FORECAST TO STEADILY INTENSIFY OVER THE NEXT 36 HOURS TO 65 KTS AS
SHEAR REMAINS LOW (AROUND 10 KTS) AND THE VORTEX MOISTENS. NEAR TAU
36, NORTHERLY SHEAR IS EXPECTED TO RISE TO AROUND 15-20 KTS AND DRY
AIR IS EXPECTED TO BEGIN PENETRATING THE VORTEX FROM THE NORTH.
THESE TWO FACTORS WILL ACT TO HALT THE INTENSIFICATION TREND AND
WEAKEN THE SYSTEM THROUGH TAU 96. AFTER TAU 96, MODELS GENERALLY
AGREE ON THE SYSTEM REMOISTENING AND SHEAR LOWERING, CAUSING 09S TO
BEGIN REINTENSIFYING. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT WITH A MERE 100 NM CROSS-TRACK SPREAD AT TAU 120 WITH
LITTLE ALONG-TRACK SPREAD. THE JTWC TRACK FORECAST IS PLACED CLOSE
TO THE MULTI-MODEL CONSENSUS WITH OVERALL HIGH CONFIDENCE. MODELS
GENERALLY AGREE ON INTENSIFICATION THROUGH TAU 36, AND THEN
WEAKENING THROUGH TAU 96 BEFORE REINTENSIFYING. HOWEVER,
INTENSITIES RANGE SIGNIFICANTLY AT TAU 36 WITH HWRF SUGGESTING 45
KTS WHILE HAFS-A SUGGESTS 80 KTS. DTOP (A RAPID INTENSIFICATION
AID) IS ALSO TRIGGERED THIS MODEL RUN, ADDING UNCERTAINTY TO THE
INTENSITY FORECAST. THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO
THE CONSENSUS WITH 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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