WDXS32 PGTW 231500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 09S (GRANT) WARNING NR 
013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.2S 99.1E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 129 NM EAST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A VERY
COMPACT YET ILL-DEFINED TROPICAL CYCLONE (TC) WHICH CONTINUES TO
BE NEGATIVELY AFFECTED BY THE ENVIRONMENT. PERSISTENT NORTHEASTERLY 
SHEAR, CURRENTLY ESTIMATED BY CIMSS TO BE RUNNING AT ABOUT 16 KNOTS, 
HAS ADVERSELY IMPACTED THE SYSTEM OVER THE PAST 6 TO 12 HOURS. 
EARLIER IN THE DAY, CONVECTION WAS ABLE TO DEVELOP AND REMAIN OVER 
THE LOW-LEVEL CIRCULATION CENTER (LLCC), WITH A NASCENT MICROWAVE EYE 
FEATURE DEVELOPING IN MICROWAVE IMAGERY FROM APPROXIMATELY 0600Z. 
HOWEVER, SINCE THAT TIME, THE CONVECTION HAS RAPIDLY DISSIPATED AND 
BECOME DISPLACED TO THE SOUTH, LEAVING BEHIND AN LLCC OBSCURED BY 
MID-LEVEL CLOUDS, WHICH WHILE EXHIBITING ROTATION, ARE NOT FORMED 
INTO A WELL-STRUCTURED ROTATION. A 231120Z GMI 37GHZ MICROWAVE IMAGE
INDICATED THAT WHILE THE OUTER BANDS ARE FAIRLY WELL FORMED, THE
INNER CORE STRUCTURE IS DISORGANIZED AND LACKS A CLEARLY DEFINED 
CENTER. THE INITIAL POSITION IS ASSESSED WITH LOW CONFIDENCE DUE TO 
THE ILL-DEFINED NATURE OF THE CORE OF THE SYSTEM AND THE OBSCURED 
LLCC IN THE INFRARED IMAGERY. THE INITIAL INTENSITY IS ASSESSED WITH
MEDIUM CONFIDENCE, BASED ON A BLEND OF THE OBJECTIVE AND SUBJECTIVE
INTENSITY ESTIMATES NOTED BELOW. ENVIRONMENTAL CONDITIONS ARE
MARGINAL, WITH MODERATE TO HIGH NORTHEASTERLY SHEAR, WEAK POLEWARD
OUTFLOW ALOFT, WARM SSTS AND DRY MID-LEVEL TO THE NORTH OF THE
SYSTEM.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   DEMS: T3.0 - 45 KTS
   APRF: T3.0 - 45 KTS
   CIMSS SATCON: 47 KTS AT 230830Z
   CIMSS ADT: 53 KTS AT 231130Z
   CIMSS AIDT: 39 KTS AT 231230Z
   CIMSS D-MINT: 38 KTS AT 231123Z
   CIMSS D-PRINT: 35 KTS AT 231230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: DRY MID-LEVEL AIR, PARTICULARLY ALONG THE
NORTHERN EXTENT OF THE CIRCULATION. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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: TROPICAL CYCLONE (TC) 09S (GRANT) IS FORECAST
TO SLOWLY TRACK NORTHWESTWARD OVER THE NEXT 12 TO 24 HOURS, ALONG
THE LOW- TO MID-LEVEL GRADIENT ALONG THE NORTHEASTERN PERIPHERY OF
THE STR CENTERED FAR TO THE SOUTHWEST. AS THE SYSTEM STRENGTHENS
AND DEEPENS VERTICALLY, IT WILL COME UNDER THE INFLUENCE OF THE A
BUILDING STR OFF THE NORTHWEST COAST OF AUSTRALIA, AND BEGIN A
GRADUAL TURN ONTO A MORE WEST-SOUTHWESTWARD TRAJECTORY AFTER TAU
48. THIS RIDGE IS FORECAST TO MOVE TOWARDS THE SOUTHWEST ALONG WITH
TC 09S, KEEPING TC 09S ON THE NORTHWEST PERIPHERY OF THE RIDGE, AND
THUS, FIRMLY ON A WEST-SOUTHWESTWARD TRACK, THROUGH THE END OF THE
FORECAST PERIOD. IN TERMS OF INTENSITY, THE SYSTEM WILL STRUGGLE TO 
CONSOLIDATE IN THE FACE OF THE PERSISTENT SHEAR IN THE NEAR-TERM. IN 
ADDITION, ITS COMPACT SIZE WILL RENDER IT PARTICULARLY SUSCEPTIBLE TO 
SMALL CHANGES IN THE ENVIRONMENT, AND THERE IS A POSSIBILITY THAT IT 
WILL WEAKEN SLIGHTLY IN THE NEXT 6 TO 12 HOURS. HOWEVER, ALL 
AVAILABLE GUIDANCE INDICATES THE ENVIRONMENT WILL IMPROVE AFTER TAU 
12, WITH GRADUALLY INCREASING MOISTURE, IMPROVED UPPER-LEVEL OUTFLOW 
AND DECREASING SHEAR. ASSUMING THE SYSTEM CAN MAINTAIN ITS STRUCTURE 
FOR ANOTHER 12 HOURS, IT IS POISED TO INTENSIFY IN THE MID-RANGE 
FORECAST, UP TO A PEAK OF APPROXIMATELY 65 KNOTS BY TAU 72. AFTER 
THAT, IT IS EXPECTED TO SUFFER FROM ANOTHER PENETRATION OF DRY AIR 
INTO THE CORE OF THE SYSTEM AND ANOTHER ROUND OF INCREASED SHEAR AS A 
TROF PASSES BY TO THE SOUTH. THESE CONDITIONS ARE NOT EXPECTED TO 
PERSIST HOWEVER, AND WHILE THE SYSTEM WILL WEAKEN A BIT AFTER TAU 72, 
IT SHOULD BE ABLE TO SURVIVE AND MAINTAIN INTENSITY AFTER TAU 96. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD OVERALL
AGREEMENT, WITH ALL MEMBERS OF THE CONSENSUS AGREEING ON THE TRACK
SCENARIO. CROSS-TRACK SPREAD BETWEEN THE GALWEM (NORTH) AND NAVGEM
(SOUTH) OUTLIERS INCREASES TO 375NM BY TAU 120, BUT THE REMAINDER
OF THE CONSENSUS MEMBERS (ECMWF, EC-AIFS, GFS, GEFS, EGRR AND FGNI)
ARE TIGHTLY GROUPED ABOUT THE CONSENSUS MEAN. THE MULTI-MODEL
ENSEMBLE PACKAGE TELLS A SIMILAR TALE, WITH ALL BUT A HANDFUL OF
MEMBERS CONFINED TO A RELATIVELY NARROW ENVELOPE POINTED TO THE
WEST-SOUTHWEST AFTER A BRIEF PERIOD OF WEST-NORTHWESTWARD MOVEMENT 
EARLY-ON IN THE FORECAST. THE JTWC FORECAST IS PLACED NEAR THE 
CONSENSUS MEAN AND THE ECMWF TRACK, WITH HIGH CONFIDENCE. INTENSITY 
GUIDANCE IS MORE MIXED, WITH THE HWRF IN PARTICULAR SHOWING A 
SIGNIFICANT SHIFT UPWARDS IN INTENSITY SINCE THE PREVIOUS RUN, NOW 
POSITIONED AT THE HIGH END OF THE ENVELOPE VICE THE LOW END. HOWEVER, 
IN THE AGGREGATE, THE INTENSITY GUIDANCE HAS COME DOWN A BIT, WITH 
ONLY THE RECENTLY MORE AGGRESSIVE HWRF REACHING 70 KNOTS. THE 
REMAINDER OF THE GUIDANCE PEAKS BETWEEN 55 AND 65 KNOTS BETWEEN TAU 
48 AND TAU 72, BEFORE WEAKENING AND THEN RE-INTENSIFYING AGAIN AFTER 
TAU 96. THE JTWC FORECAST IS POSITIONED NEAR THE CONSENSUS MEAN 
THROUGH TAU 48, THEN WITHIN APPROXIMATELY FIVE KNOTS OF THE HWRF FOR 
THE REMAINDER OF THE FORECAST.    

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