WDPN31 PGTW 072100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 09W (BAVI) WARNING NR
028//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.8N 135.3E
   INITIAL INTENSITY: 130 KTS
   GEOGRAPHIC REFERENCE: 716 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 50 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS SUPER
TYPHOON (STY) 09W (BAVI) WITH A RAGGED EYE FEATURE SURROUNDED BY AN
EXPANSIVE CENTRAL DENSE OVERCAST (CDO) THAT HAS ALSO BECOME A BIT
MORE RAGGED OVER THE PAST SEVERAL HOURS. CLOUD TOP TEMPERATURES IN
THE CDO, AS SEEN IN ANIMATED BD-ENHANCED INFRARED IMAGERY, HAVE
OSCILLATED BETWEEN PERIODS OF WARMING AND COOLING OVER THE PAST 6
HOURS AS WELL. PERSISTENT NORTHEASTERLY VERTICAL WIND SHEAR (VWS)
IS ALSO EVIDENT IN A 071941Z SSMIS 91GHZ IMAGE DEPICTING A
PRONOUNCED EROSION OF THE EYEWALL IN THE NORTHEASTERN QUADRANT. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE CENTER
OF THE EYE IN EIR IMAGERY. THE INITIAL INTENSITY OF 130 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES OF
T6.5-7.0 AND THE SPREAD OF CIMSS OBJECTIVE INTENSITY ESTIMATES. SEA
SURFACE TEMPERATURES THAT HAVE REMAINED AT 29-30 C AND ROBUST
EQUATORWARD OUTFLOW ARE BEING OFFSET BY THE PERSISTENT 20-25 KT
VWS, MAKING THE ENVIRONMENTAL ASSESSMENT MARGINALLY FAVORABLE.

INITIAL WIND RADII BASIS: PERSISTENCE

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 OKINAWA.

AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T6.5 - 127 KTS
   RJTD: T6.5 - 127 KTS
   RCTP: T7.0 - 140 KTS
   KNES: T6.5 - 127 KTS
   CIMSS SATCON: 141 KTS AT 071800Z
   CIMSS ADT: 129 KTS AT 071800Z
   CIMSS AIDT: 118 KTS AT 071800Z
   CIMSS D-MINT: 127 KTS AT 071628Z
   CIMSS D-PRINT: 129 KTS AT 071800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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: SUPER TYPHOON BAVI MAINTAINED A NEARLY DUE
WESTWARD TRAJECTORY OVER THE PAST 6 HOURS AT A SLOWER 12 KT RATE OF
ADVANCE. THE STR NOW CENTERED OVER KYUSHU THAT HAD PREVIOUSLY BEEN
THE PRIMARY STEERING INFLUENCE IS EXPECTED TO CONTINUE MIGRATING
EASTWARD AND MERGE WITH THE STR CENTERED TO THE NORTHEAST OVER THE
NEXT 36 HOURS. UNDER THIS STEERING REGIME, STY 09W IS FORECAST TO
MAINTAIN A WEST-NORTHWESTWARD TRAJECTORY OVER THE NEXT 24 HOURS,
THEN TURN TO A NORTHWESTWARD TRACK FOR THE REMAINDER OF THE
FORECAST PERIOD. THE CENTER OF THE SYSTEM IS EXPECTED TO PASS JUST
NORTHEAST OF TAIWAN WITH A CPA TO TAIPEI AT 110500Z BEFORE MAKING
LANDFALL IN EASTERN CHINA. NOTABLY, 09W IS EXPECTED TO RETAIN AN
EXPANSIVE (AROUND 500 NM DIAMETER) STORM FORCE WIND FIELD UNTIL IT
MAKES LANDFALL. MARGINALLY FAVORABLE ENVIRONMENTAL CONDITIONS ARE
EXPECTED TO ALLOW THE SYSTEM TO MAINTAIN AN INTENSITY OF 130 KTS
FOR THE NEXT 12 HOURS, FOLLOWED BY A PERIOD OF GRADUAL WEAKENING
DUE TO PERSISTENT NORTHEASTERLY SHEAR THROUGH TAU 72. MORE RAPID
WEAKENING IS FORECAST AFTER TAU 72 AS THE SYSTEM INTERACTS WITH THE
ISLAND OF TAIWAN AND MAKES ITS EVENTUAL LANDFALL OVER EASTERN
CHINA.

MODEL DISCUSSION: MODEL TRACK GUIDANCE REMAINS IN GOOD AGREEMENT
ABOUT THE WEST-NORTHWESTWARD TURNING NORTHWESTWARD SCENARIO, WITH A
CROSS-TRACK SPREAD OF 100 NM AT TAU 72 AS 09W APPROACHES TAIWAN.
WITH NAVGEM AND ECMWF DETERMINISTIC MODELS ON THE SOUTHWESTERN EDGE
OF THE ENVELOPE AND AI SOLUTIONS MAKING UP THE NORTHEASTERN EDGE.
THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE MULTI-MODEL
CONSENSUS THROUGHOUT THE FORECAST PERIOD, WITH HIGH CONFIDENCE
THROUGH TAU 72 AND MEDIUM CONFIDENCE FROM TAU 72 TO TAU 120 AS THE
CROSS-TRACK SPREAD INCREASES TO 220 NM AFTER LANDFALL. WITH THE
EXCEPTION OF DECAY SHIPS, WHICH SUGGESTS A SIGNIFICANTLY FASTER
RATE OF WEAKENING, THE LATEST INTENSITY GUIDANCE REMAINS IN GOOD
AGREEMENT ABOUT THE GRADUAL WEAKENING TREND FOLLOWED BY RAPID DECAY
AFTER LANDFALL. THE JTWC INTENSITY FORECAST FOLLOWS CLOSELY TO THE
MULTI-MODEL CONSENSUS THROUGHOUT THE FORECAST PERIOD WITH MEDIUM
CONFIDENCE.

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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