WDXS32 PGTW 251500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 22S (GARANCE)   
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.3S 51.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 233 NM NORTHWEST OF ST DENIS
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY-
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) OBSCURED BENEATH A REGION 
OF FLARING DEEP CONVECTION. THE INITIAL POSITION IS PLACED WITH HIGH 
CONFIDENCE BASED ON THE MSI. A 251047Z PARTIAL AMSR2 89GHZ MICROWAVE 
IMAGE REVEALS DEEP CONVECTIVE BANDING WRAPPING FROM THE WESTERN 
QUADRANT INTO THE NORTHERN QUADRANT OF THE SYSTEM. THE OVERALL 
CONVECTIVE STRUCTURE HAS IMPROVED SLIGHTLY DESPITE THE STRONG 
SOUTHERLY VERTICAL WIND SHEAR (VWS) EVIDENT ON ANIMATED WATER VAPOR 
IMAGERY, WITH RECENT ASCAT DATA INDICATING 30-35 KNOT WINDS OVER THE 
NORTHERN SEMICIRCLE. DUE TO THE RECENT BURST OF CENTRAL CONVECTION, 
DVORAK INTENSITY ESTIMATES HAVE INCREASED UP TO 35 KNOTS USING THE 
SHEAR METHOD, WHICH SUPPORTS THE DECISION TO ISSUE THE FIRST WARNING.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: LOW-LEVEL NEAR-EQUATORIAL RIDGE
POSITIONED TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   FMEE: T2.5 - 35 KTS
   CIMSS D-PRINT: 38 KTS AT 251200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 25-30 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 22S IS TRACKING SLOWLY 
EASTWARD TO EAST-NORTHEASTWARD UNDER THE STEERING INFLUENCE OF A WEAK 
NEAR-EQUATORIAL RIDGE (NER) POSITIONED TO THE NORTH. THIS TRACK MOTION 
WILL CONTINUE UNTIL ABOUT TAU 36 WHEN THE SYSTEM WILL TRANSITION TO 
THE STEERING INFLUENCE OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) 
POSITIONED TO THE EAST, WHICH WILL RESULT IN A SHARP SOUTHWARD TURN BY 
TAU 48. THE SYSTEM WILL INTENSIFY SLOWLY THROUGH TAU 12 DUE TO THE 
PERSISTENT HIGH VWS. HOWEVER, VWS WILL GRADUALLY DECREASE AFTER
TAU 12 ALLOWING THE SYSTEM TO CONSOLIDATE AND INTENSIFY AT A FASTER
RATE, WITH A MODERATE CHANCE OF RAPID INTENSIFICATION FROM TAU 36
TO TAU 72 WHEN A VIGOROUS EQUATORWARD OUTFLOW CHANNEL IS ESTABLISHED. 
BY TAU 72, TC 22S WILL ACCELERATE SOUTHWARD THEN RECURVE SOUTHEASTWARD 
AFTER TAU 96. SUBSTANTIAL WEAKENING IS EXPECTED AFTER TAU 96 AS THE 
SYSTEM BEGINS TO INTERACT WITH NEAR JET STRENGTH SUBTROPICAL 
WESTERLIES. THE HIGH VWS (25-30 KNOTS) IN CONCERT WITH COOL SST VALUES 
(23-24C) WILL SERVE TO STEADILY WEAKEN THE SYSTEM. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN FAIR AGREEMENT
WITH A 140-180 NM CROSS-TRACK SPREAD FROM TAU 96 TO TAU 120. EPS
AND GEFS PROBABILISTIC MODEL GUIDANCE SUPPORTS THE JTWC TRACK
FORECAST WITH MEDIUM CONFIDENCE. RELIABLE INTENSITY GUIDANCE
SUPPORTS THE JTWC INTENSITY FORECAST WITH MEDIUM CONFIDENCE, WITH
HAFS-A AND HWRF INDICATING A PEAK INTENSITY OF ABOUT 80 KNOTS AT
TAU 60.    

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