WDPN32 PGTW 120300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 15W (BOLAVEN)        
WARNING NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.6N 143.0E
   INITIAL INTENSITY: 150 KTS
   GEOGRAPHIC REFERENCE: 269 NM SOUTH-SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 50 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
SUPER TYPHOON (STY) 15W IS CURRENTLY GOING THROUGH AN EYEWALL
REPLACEMENT CYCLE (ERC) AS PREDICTED BY THE CIMSS M-PERC PRODUCT.
AN 112341Z GMI 89 GHZ COLOR COMPOSITE MICROWAVE IMAGE DEPICTS A
DEVELOPING OUTER EYEWALL AND WELL-DEFINED MOAT FEATURE SURROUNDING
THE SMALL, INTENSE INNER EYEWALL. CONSEQUENTLY, ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY SHOWS THAT THE SYSTEM HAS WEAKENED
SLIGHTLY WITH WARMING CLOUD TOP TEMPERATURES AND A MORE ASYMMETRIC,
RAGGED CONVECTIVE STRUCTURE. IN GENERAL, OBJECTIVE INTENSITY ESTIMATES 
(ADT, AIDT, DPRINT) HAVE DECREASED MODESTLY AND NOW RANGE FROM 144 TO 
149 KNOTS. THE SUBJECTIVE DVORAK ESTIMATES VARY WITH FINAL-T ESTIMATES 
RANGING FROM T7.0 (140 KTS) TO T7.5 (155 KTS). BASED ON THE SLIGHT 
WEAKENING TREND, THE INITIAL INTENSITY IS NOW ASSESSED AT 150 KNOTS 
WITH MEDIUM CONFIDENCE. THE INITIAL POSITION IS PLACED WITH HIGH 
CONFIDENCE BASED ON A 9 NM ROUND EYE IN EIR IMAGERY. THE CIMSS M-PERC 
PRODUCT SHOWS A PEAK ERC ONSET PROBABILITY OF 95 PERCENT AT 120000Z, 
WHICH INDICATES ANOTHER ERC IS LIKELY WITHIN THE NEXT DAY OR SO.

INITIAL WIND RADII BASIS: SENTINEL-1A SAR DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.5 - 155 KTS
   RJTD: T7.5 - 155 KTS
   KNES: T7.5 - 155 KTS
   CIMSS ADT: 149 KTS AT 120000Z
   CIMSS ADT: 147 KTS AT 120000Z
   CIMSS DPRINT: 144 KTS AT 120200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL

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 IS TRACKING POLEWARD ALONG THE WESTERN 
PERIPHERY OF THE STR, TOWARD A BREAK IN THE STR ASSOCIATED WITH A DEEP 
MIDLATITUDE SHORTWAVE TROUGH. THIS TROUGH IS CLEARLY EVIDENT IN 
ANIMATED WATER VAPOR IMAGERY AS WELL AS IN THE RECENT SOUNDINGS FROM 
THE RYUKYU ISLANDS AND CHICHI-JIMA. STY 15W IS FORECAST TO GRADUALLY 
TURN NORTHEASTWARD THROUGH TAU 36 WITH STEADY WEAKENING, INITIALLY 
RESULTING FROM A SERIES OF ERC EVENTS THEN WITH INCREASING VERTICAL 
WIND SHEAR (VWS) AFTER TAU 24. STY BOLAVEN IS FORECAST TO WEAKEN 
RAPIDLY AFTER TAU 36 AS IT BEGINS EXTRA-TROPICAL TRANSITION (ETT) AND 
ACCELERATES NORTHEASTWARD. VWS IS EXPECTED TO INCREASE QUICKLY TO HIGH 
LEVELS (30-43 KNOTS) THEN MORE SUBSTANTIALLY (50 KNOTS) NEAR TAU 60 AS 
THE SYSTEM BECOMES EMBEDDED IN THE WESTERLIES NEAR THE JET. STY 15W 
WILL COMPLETE ETT BY TAU 72 AS IT GAINS FRONTAL CHARACTERISTICS AND 
TRACKS UNDER THE JET WITH VERY HIGH (80 KNOTS) VWS AND COOL SST (22 C) 
VALUES. HOWEVER, THE SYSTEM IS EXPECTED TO MAINTAIN STORM-FORCE WINDS 
AS IT TRACKS SOUTH OF THE ALEUTIAN ISLANDS AND INTO THE GULF OF ALASKA.   

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN TIGHT AGREEMENT 
THROUGH TAU 48 WITH A 90 NM CROSS-TRACK SPREAD IN SOLUTIONS AT TAU 48. 
ALTHOUGH RELIABLE INTENSITY GUIDANCE (HAFS-A, COAMPS-TC, HWRF) INDICATE 
STEADY WEAKENING, THERE IS SOME UNCERTAINTY IN THE PEAK INTENSITY OVER 
THE NEXT 12 HOURS WITH POTENTIAL FOR SLIGHT INTENSIFICATION (DUE TO 
ENHANCED POLEWARD OUTFLOW) TO 155-160 KNOTS BEFORE THE WEAKENING TREND 
COMMENCES. AFTER TAU 48, MODEL GUIDANCE GRADUALLY DIVERGES WITH 
INCREASING UNCERTAINTY IN BOTH THE CROSS-TRACK (200 NM SPREAD AT TAU 
72) AND ALONG-TRACK (300 NM SPREAD AT TAU 72) PORTIONS OF THE JTWC 
FORECAST TRACK. THEREFORE, THERE IS HIGH TRACK CONFIDENCE THROUGH TAU 
48 AND MEDIUM CONFIDENCE AFTER TAU 48 WITH MEDIUM OVERALL CONFIDENCE.

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