WDXS33 PGTW 270900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 22S (GARANCE) WARNING 
NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.2S 55.3E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 133 NM NORTH OF ST DENIS
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A 15NM
RAGGED EYE FEATURE WITH DEEP CONVECTIVE BANDS WRAPPING AROUND THE
NORTHWEST AND NORTHEAST INTO THE CENTER. CLEAR DRY AIR BORDERS THE
WESTERN PERIPHERY OF THE TROPICAL CYCLONE (TC). WATER VAPOR IMAGERY
REVEALS POLEWARD AND EASTWARD OUTFLOW. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED ANIMATED
EIR AND AN EARLIER 270216Z 91GHZ MICROWAVE IMAGE. THE INITIAL
INTENSITY OF 105 KTS IS ASSESSED WITH LOW CONFIDENCE BASED ON THE
AGENCY AND OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   KNES: T5.5 - 102 KTS
   DEMS: T4.0 - 65 KTS
   ABRF: T5.5 - 102 KTS
   CIMSS SATCON: 78 KTS AT 270258Z
   CIMSS ADT: 35 KTS AT 270600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: LOW
   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) 22S WILL CONTINUE TO BE
DRIVEN BY A SUBTROPICAL RIDGE LOCATED TO THE EAST. IN THE NEAR-TERM
FORECAST, THE SYSTEM WILL TRACK POLEWARD FOR THE FIRST 48 HOURS,
THEN WILL CURVE SOUTHEASTWARD AFTER PASSING THE RIDGE AXIS. THE
SYSTEM WILL REMAIN IN A FAVORABLE ENVIRONMENT FOR THE FIRST 24
HOURS OF THE FORECAST, ALLOWING FOR THE PEAK INTENSITY OF 105KTS.
HIGH VERTICAL WIND SHEAR WILL ERODE THE CIRCULATION AFTER TAU 24,
INITIATING A DECLINE IN INTENSITY THROUGH THE END OF THE FORECAST
PERIOD. THE VERTICAL WIND SHEAR WILL REMAIN UNFAVORABLE ABOVE
20KTS, AND BAROCLINIC FORCING BETWEEN TAU 72-96 WILL RESULT IN
EXTRATROPICAL TRANSITION.

MODEL DISCUSSION: THE DETERMINISTIC MODEL GUIDANCE IS IN GOOD
AGREEMENT THAT TC 22S WILL TRACK SOUTHWARD AND THEN SOUTHEASTWARD
ON THE PERIPHERY OF THE SUBTROPICAL RIDGE. THE MAXIMUM CROSS-TRACK
SPREAD BY TAU 96 IS 350NM DUE TO VARYING INTERPRETATIONS OF THE
STRENGTH OF THE RIDGE. THE INTENSITY GUIDANCE IS IN GOOD AGREEMENT
THAT THE SYSTEM WILL STAGNATE OR SLIGHTLY INTENSIFY OVER THE FIRST
12 HOURS BEFORE GRADUALLY WEAKENING THROUGH EXTRATROPICAL
TRANSITION.

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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