WDPN31 PGTW 080900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 09W (BAVI) WARNING NR 
030//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.9N 133.0E
   INITIAL INTENSITY: 135 KTS
   GEOGRAPHIC REFERENCE: 645 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 50 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SUPER
TYPHOON 09W (BAVI) WITH WARMING CLOUD TOPS AND DEGRADING SYMMETRY
IN THE CENTRAL DENSE OVERCAST THAT IS SURROUNDING THE EYEWALL. A
080409Z AMSR2 89 GHZ MICROWAVE IMAGE REVEALED A MUCH LARGER OUTER
EYEWALL THAT IS BEGINNING TO FORM WHILE THE 36 GHZ VERSION OF THE
SAME IMAGE SHOWED A DISTINCT MOAT FEATURE FORMING DIRECTLY OUTWARD
OF THE MAIN INNER-CORE. THE BEGINNING OF AN EYEWALL REPLACEMENT
CYCLE ALONG IN COMBINATION WITH NOW HIGH (25-30 KTS) NORTHEASTERLY
VERTICAL WIND SHEAR IS ASSESSED TO BE THE CAUSE OF THE DEGRADATION
OVER THE PAST 6 HOURS. THE 89 GHZ AMSR2 MICROWAVE IMAGE ALSO
REVEALED A PROMINENT WEAKNESS WITHIN THE NORTHEASTERN QUADRANT OF
THE EYEWALL, LIKELY IN RESPONSE TO THE STRONG VWS IMPACTING THE
SYSTEM FROM THAT DIRECTION. ENVIRONMENTAL ANALYSIS INDICATES THAT
09W IS NOW IN A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY
STRONG RADIAL OUTFLOW ALOFT AND WARM (29-30 C) SEA SURFACE
TEMPERATURES OFFSET BY HIGH NORTHEASTERLY VERTICAL WIND SHEAR. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EYE IN
ANIMATED MSI. THE INITIAL INTENSITY OF 135 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND CIMSS
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: A COMBINED STEERING INFLUENCE FROM THE
WESTERN EXTENSION OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE
NORTHEAST AND THE SOUTHWESTERN EXTENSION OF A SEPARATE STR CENTERED
OVER KYUSHU.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   RJTD: T6.5 - 127 KTS
   RCTP: T7.0 - 140 KTS 
   KNES: T7.0 - 140 KTS 
   CIMSS SATCON: 122 KTS AT 080600Z
   CIMSS ADT: 127 KTS AT 080600Z
   CIMSS AIDT: 137 KTS AT 080600Z
   CIMSS D-MINT: 130 KTS AT 080424Z
   CIMSS D-PRINT: 130 KTS AT 080600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: 09W IS FORECAST TO TRACK WEST-NORTHWESTWARD
UNDER THE INFLUENCE OF THE COMBINED STEERING INFLUENCE THROUGH TAU
12. AFTER TAU 12, THE STR THAT IS CURRENTLY POSITIONED OVER KYUSHU
WILL MERGE WITH THE STR THAT IS CURRENTLY SITUATED TO THE NORTHEAST
OF 09W. ONCE THIS MERGE OCCURS, THE RESULTING STR WILL GUIDE 09W IN
A MORE NORTHWESTWARD DIRECTION THROUGH THE REMAINDER OF THE
FORECAST PERIOD. A TRACK THROUGH THE YAEYAMA ISLANDS IS EXPECTED TO
OCCUR BETWEEN TAU 60 AND 72 WITH A FINAL LANDFALL FORECAST TO TAKE
PLACE ALONG THE EASTERN COAST OF CHINA AROUND TAU 84. IN TERMS OF
INTENSITY, 09W IS FORECAST TO CONTINUE STEADILY WEAKENING THROUGH
TAU 24 UNDER THE INFLUENCE OF THE HIGH NORTHEASTERLY VERTICAL WIND
AND POTENTIAL EYEWALL REPLACEMENT CYCLE. AFTER TAU 24, THE
INTENSITY IS FORECAST TO MOMENTARILY STABILIZE AS SHEAR DROPS OFF TO
BELOW 15 KTS. NEAR TAU 60, 09W IS EXPECTED TO ENTER AN AREA OF MUCH
LOWER OCEAN HEAT CONTENT (BELOW 25 KJ), TRIGGERING ANOTHER BOUT OF
WEAKENING AS THE SYSTEM APPROACHES THE COAST OF CHINA. AFTER
LANDFALL, TERRAIN INTERACTION WILL CAUSE THE VORTEX TO RAPIDLY
DETERIORATE WITH DISSIPATION FORECAST TO OCCUR AROUND TAU 120, WEST
OF SHANGHAI.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 72 WITH NO SIGNIFICANT OUTLIERS. CROSS-TRACK
SPREAD AT TAU 72 IS AROUND 105 NM, AND THE JTWC TRACK FORECAST IS
PLACED CLOSE TO THE CONSENSUS THROUGH THAT TIME WITH HIGH
CONFIDENCE. AFTER TAU 72, MODELS BEGIN TO FAN OUT A BIT, ESPECIALLY
AFTER TAU 96, ONCE THE VORTEX BECOMES SHALLOW OVER MAINLAND CHINA.
CROSS-TRACK SPREAD AT TAU 120 INCREASES TO OVER 300 NM WITH NAVGEM
BEING THE SOUTHERNMOST MODEL AND THE EC-AIFS BEING THE NORTHERNMOST
MODEL. AFTER TAU 120, THE JTWC TRACK FORECAST IS PLACED CLOSER TO
THE ECMWF AND GFS ENSEMBLE MEANS WITH MEDIUM CONFIDENCE. INTENSITY
GUIDANCE AGREES ON GRADUAL WEAKENING THROUGH TAU 72 FOLLOWED BY A
MORE RAPID RATE OF WEAKENING AFTERWARD WITH NO SIGNIFICANT
VARIATION BETWEEN RELIABLE INTENSITY GUIDANCE. THE JTWC INTENSITY
FORECAST IS PLACED CLOSE TO THE CONSENSUS WITH OVERALL MEDIUM
CONFIDENCE DUE TO INHERENT UNCERTAINTIES REVOLVING AROUND THE
POTENTIAL EYEWALL REPLACEMENT CYCLE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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