WDPN32 PGTW 122100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 15W (BOLAVEN)       
WARNING NR 024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.0N 145.4E
   INITIAL INTENSITY: 145 KTS
   GEOGRAPHIC REFERENCE: 229 NM EAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 50 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AFTER A VERY BRIEF PERIOD OF REINTENSIFICATION TO 155 KNOTS (SUPPORTED 
BY A 120837Z RSAT2 PASS), SUPER TYPHOON (STY) HAS CLEARLY STARTED TO 
WEAKEN AS INDICATED IN ANIMATED ENHANCED INFRARED (EIR) SATELLITE 
IMAGERY, WHICH SHOWS A MORE ASYMMETRIC CONVECTIVE CORE, DUE TO 
INCREASING WEST-SOUTHWESTERLY VERTICAL WIND SHEAR (VWS), AND COOLING 
EYE TEMPERATURES OF +5.5 C. THE INITIAL POSITION IS PLACED WITH HIGH 
CONFIDENCE BASED ON A 12 NM ROUND EYE IN EIR IMAGERY. THE INITIAL 
POSITION IS ALSO SUPPORTED BY A MICROWAVE EYE FEATURE IN THE 121844Z 
SSMIS 91 GHZ COLOR COMPOSITE MICROWAVE IMAGE. AS INDICATED BY THE 
CIMSS M-PERC PRODUCT, THE SYSTEM IS GOING THROUGH AN EYEWALL 
REPLACEMENT CYCLE WITH CONCENTRIC EYEWALLS SEPARATED BY A CLEAR MOAT 
FEATURE. DUE TO THE INCREASING VWS AND DRY AIR, THE WESTERN PORTION OF 
THE OUTER EYEWALL HAS ERODED WITH A LARGE BREAK EVIDENT IN THE SSMIS
MICROWAVE IMAGE. SUBJECTIVE DVORAK FINAL-T ESTIMATES HAVE DECREASED
AS LOW AS T6.5 (127 KTS) WITH CURRENT INTENSITY VALUES RANGING FROM
7.0 TO 7.5 (140-155 KTS). THE INITIAL INTENSITY IS ASSESSED AT 145 
KNOTS WITH MEDIUM CONFIDENCE BASED ON THE DVORAK CURRENT INTENSITY 
ESTIMATES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE EAST AND SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.5 - 155 KTS
   RJTD: T7.5 - 155 KTS
   KNES: T7.0 - 140 KTS 
   CIMSS ADT: 140 KTS AT 121800Z
   CIMSS AIDT: 139 KTS AT 121800Z
   CIMSS DPRINT: 131 KTS AT 121800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENCROACHING OVER THE WESTERN SEMICIRCLE. 

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: STY 15W IS ACCELERATING NORTHEASTWARD ALONG THE 
NORTHWESTERN PERIPHERY OF THE STR AND IS EXPECTED TO CONTINUE ON A 
NORTHEASTWARD TRAJECTORY THROUGH THE FORECAST PERIOD WITH STEADY 
WEAKENING DUE TO INCREASING VWS AND DRY AIR ENTRAINMENT. STY 15W WILL 
BEGIN EXTRA-TROPICAL TRANSITION (ETT) BY TAU 12 AS IT BEGINS TO 
INTERACT WITH THE BAROCLINIC ZONE. AFTER TAU 24, STY 15W WILL WEAKEN 
RAPIDLY DUE TO STRONG VWS (30-50 KTS). STY 15W WILL COMPLETE ETT BY 
TAU 48 AS IT GAINS FRONTAL CHARACTERISTICS AND TRACKS UNDER THE JET 
WITH VWS IN EXCESS OF 60 KNOTS. THE SYSTEM IS FORECAST TO REMAIN A 
HURRICANE FORCE EXTRA-TROPICAL LOW AS IT TRACKS SOUTH OF THE ALEUTIAN 
ISLANDS.     

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN 
EXCEPTIONALLY TIGHT AGREEMENT WITH A 100 NM CROSS-TRACK SPREAD AT TAU 
48. INTENSITY GUIDANCE IS IN GOOD AGREEMENT AS WELL WITH RAPID 
WEAKENING INDICATED IN BOTH THE GLOBAL AND MESOSCALE MODELS.  

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