WDPN31 PGTW 100300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (BAVI) WARNING NR 037//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.8N 127.3E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 343 NM SOUTH OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THAT TYPHOON
09W (BAVI) CONTINUES TO STRUGGLE MIGHTILY TO GENERATE DEEP
CONVECTION WITH ANY DURABLE COVERAGE. MOST CONVECTION IS CONFINED
NEAR THE CIRCULATION CENTER AND TO ITS SOUTH WITH A RAGGED
APPEARANCE. A 092301Z SSMIS MICROWAVE PASS SHOWED ONLY A PARTIAL
INNER EYEWALL IN THE SOUTHEAST QUADRANT, WITH A SECONDARY
CONCENTRIC BAND OR EYEWALL AT ABOUT 80 NM RADIUS FROM THE CENTER.
GIVEN THE OTHERWISE FAVORABLE ENVIRONMENT, IT IS LIKELY THAT
DYNAMIC OCEAN COOLING BENEATH BAVI'S MASSIVE WIND FIELD IS ACTIVELY
REDUCING HEAT FLUXES INTO THE STORM AND UNDERMINING CONVECTIVE
DEVELOPMENT. A 092128Z SENTINEL-1D SAR IMAGE CONTINUED TO SHOW A
HIGHLY BROAD CORE WIND FIELD ASSOCIATED WITH THE STILL INCOMPLETE
EYEWALL REPLACEMENT CYCLE THAT BEGAN ABOUT 36 HOURS AGO. THE
INITIAL INTENSITY IS LOWERED TO 75 KT BASED ON THIS SAR DATA AND A
BLEND OF OTHER AGENCY DVORAK AND OBJECTIVE SATELLITE-BASED
INTENSITY ESTIMATES. DESPITE BEING LOCATED ABOUT 340 NM SOUTH OF
OKINAWA, 09W'S MASSIVE WIND FIELD IS ALREADY BEGINNING TO IMPACT
THE REGION. SURFACE OBSERVATIONS FROM THE JAPAN METEOROLOGICAL
AGENCY INDICATE THAT WINDS ARE APPROACHING GALE FORCE AT MINAMI
DAITO JIMA, AND OKINAWA HAS OBSERVED WINDS OF 25 TO 30 KT IN RECENT
HOURS.

INITIAL WIND RADII BASIS: AMSR-2 DATA

CURRENT STEERING MECHANISM: STR SOUTH OF JAPAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T4.0 - 65 KTS
   CIMSS D-MINT: 78 KTS AT 092301Z
   CIMSS D-PRINT: 71 KTS AT 092330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 27-29 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TYPHOON 09W (BAVI) CONTINUES TO WEAKEN MORE
THAN ORIGINALLY FORECAST, LIKELY DUE TO MORE OCEANIC UPWELLING THAN
COUPLED MODELS PREDICTED. THIS IS ALSO STALLING THE PROGRESS OF THE
ONGOING EYEWALL REPLACEMENT CYCLE (ERC) AND KEEPING THE CORE WIND
FIELD PROFILE VERY FLAT AND BROAD, WHICH WILL RESIST SPIN-UP EVEN
IF OCEANIC CONDITIONS IMPROVE. WITH AN OTHERWISE FAVORABLE
ENVIRONMENT, A STEADY-STATE BALANCE SHOULD BE REACHED AT SOME
POINT. THE JTWC INTENSITY FORECAST HOLDS BAVI FLAT AT AROUND 75 KT
THROUGH LANDFALL IN CHINA, BUT SOME FLUCTUATIONS ARE POSSIBLE DUE
TO CHANGES IN OCEANIC CONDITIONS THAT CANNOT BE EASILY ANTICIPATED.
THE JTWC TRACK FORECAST TAKES BAVI AROUND THE SOUTHWESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE OFF OF MAINLAND JAPAN, CARRYING
THE STORM NEAR ISHIGAKIJIMA, JAPAN BETWEEN TAUS 12 AND 24, THEN
INTO EASTERN CHINA BETWEEN TAUS 36 AND 48. RAPID DECAY AND EVENTUAL
DISSIPATION BY TAU 72 IS EXPECTED, THOUGH A SWATH OF ELEVATED WINDS
MAY CONTINUE DRIVING NORTHWARD UP THE CHINESE COASTLINE DUE TO THE
LARGE SIZE OF THE REMNANT CIRCULATION.

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS PLACED WITH HIGH
CONFIDENCE NEAR A BLEND OF THE PHYSICS-BASED MODEL CONSENSUS AND
THE AI-BASED MODEL CONSENSUS. THE JTWC INTENSITY FORECAST IS CLOSE
TO A BLEND OF THE OCEAN-COUPLED HAFS-A, HWRF, AND COAMPS-TC WITH
MEDIUM CONFIDENCE.

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