WDXS32 PGTW 260900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 06S (ANGGREK) WARNING 
NR 023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.9S 86.5E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 1009 NM SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 42 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND ENHANCED
INFRARED (EIR) IMAGERY DEPICT TROPICAL CYCLONE (TC) 06S (ANGGREK)
TRAVELING WEST-SOUTHWESTWARD AT 11 KTS WITH A TIGHT, CLOUD-FILLED
EYE. THE EIR IMAGERY INDICATES EYE TEMPERATURES ABOVE 15C, WHILE
CLOUD-TOP TEMPERATURES REACH AS COLD AS -80C AS THE STORM HAS
INTENSIFIED OVER THE LAST TWELVE HOURS. MODERATE RADIAL OUTFLOW,
LOW LEVELS OF VERTICAL WIND SHEAR BETWEEN 5-10KTS AND FAVORABLE SEA
SURFACE TEMPERATURES BETWEEN 27-28C CONTINUE TO ENCOURAGE
INTENSIFICATION. THE INITIAL POSITION OF 16.9S 86.5E WAS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE EYE POSITION IN A 260525Z EWS-G2
IMAGE. THE INITIAL INTENSITY WAS ASSESSED WITH HIGH CONFIDENCE
BASED ON AN RCM-1 252341Z PASS SHOWING 105KT MAXIMUM WINDS AS WELL
AS THE AGENCY AND OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: THE NORTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   KNES: T6.0 - 115 KTS
   FMEE: T5.5 - 102 KTS
   CIMSS SATCON: 94 KTS AT 26645Z
   CIMSS ADT: 109 KTS AT 260315Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   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 06S IS ANTICIPATED TO RIDE THE PERIPHERY OF
THE STR TO THE SOUTHEAST, TAKING THE STORM TRACK WEST-SOUTHWEST
THROUGH TAU 48. THE STRONG RIDGE REMAINS IN PLACE THROUGH THE END
OF TAU 120 AS TC 06S CURVES SOUTHWEST AND THEN SOUTHEAST ALONG THE
PERIPHERY OF THE STR. LOW LEVELS OF VERTICAL WIND SHEAR AND
FAVORABLE SEA SURFACE TEMPERATURES WILL PERMIT THE SYSTEM TO
INTENSIFY OVER THE COURSE OF THE NEXT 48 HOURS TO AN ANTICIPATED
120KTS BEFORE THE STORM BEGINS TO GENERALLY DECREASE IN INTENSITY
STARTING AT TAU 60 DUE TO A LOSS OF OUTFLOW CHANNEL AND POTENTIAL
CONVERGENCE ALOFT. THE WEAKENING IS EXPECTED TO AMPLIFY BEYOND TAU
72 RESULTING FROM THE INTRODUCTION OF DRY AIR ENTRAINING INTO THE
SYSTEM AND VERTICAL WIND SHEAR INCREASING AS THE STORM TRANSITS
SOUTH. TC 06S WILL ULTIMATELY BE DECAPITATED BY DRY AIR AND STRONG
WIND SHEAR AT TAU 120, WHICH WILL SIGNIFICANTLY LOWER THE INTENSITY
TO 80KTS.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
IN TERMS OF TC 06S TRACK AS SHOWN BY A SMALL CROSS-TRACK
DIFFERENTIAL AT TAU 48 OPENING TO A 200NM CROSS-TRACK DIFFERENTIAL
BY TAU 120. JTWC CONSENSUS MEMBERS ARE IN GENERAL AGREEMENT THAT
THE STORM WILL INTENSIFY THROUGH TAU 48-60 BEFORE LOSING INTENSITY
THROUGH TAU 60-120. ONE OUTLIER IS COAMPS-TC, WHICH ANTICIPATES AN
INITIAL DECREASE IN INTENSITY TO 90KTS BY TAU 36, AND INCREASES TO
120KTS BY TAU 72 BEFORE LOSING STEAM THROUGH THE END OF THE
FORECAST. ANALYSIS MAY SUGGEST THAT COAMPS-TC IS PICKING UP ON AN
EYEWALL REPLACEMENT CYCLE, EXPLAINING THE DRASTIC DIFFERENCE. HWRF
ALSO IS AN EXTREME OUTLIER TAKING THE STORM INTENSITY UP TO 140KTS
AROUND TAU 48-60 AND BRINGING IT TO A DRASTIC DECLINE AT 40KTS BY
TAU 120.  

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