WDPN31 PGTW 031500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (BAVI) WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.8N 153.1E
   INITIAL INTENSITY: 125 KTS
   GEOGRAPHIC REFERENCE: 482 NM EAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) IMAGERY DEPICTS A LARGE, SYMMETRIC
CYCLONE WITH A WELL-DEFINED EYE. THE DVORAK-ENHANCED INFRARED
CHANNEL SHOWS A SYMMETRIC CENTRAL DENSE OVERCAST COMPLETELY
SURROUNDING THE EYE WITH VERY WARM TEMPERATURES WITHIN THE
SUBSIDENT REGION OF THE CENTRAL EYE. ANIMATED WATER VAPOR IMAGERY
ILLUSTRATES CONTINUED ROBUST RADIAL OUTFLOW, UNINHIBITED IN THE
CURRENT LOW SHEAR ENVIRONMENT. THE INITIAL POSITION IS ASSESSED
WITH HIGH CONFIDENCE BASED ON THE WELL-DEFINED EYE FEATURE IN THE
EIR IMAGERY. THE INITIAL INTENSITY OF 125 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND CIMSS
OBJECTIVE INTENSITY AIDS. THE ENVIRONMENT IS CHARACTERIZED AS
HIGHLY FAVORABLE FOR CONTINUED RAPID INTENSIFICATION, WITH LOW
(5-10 KTS) DEEP-LAYER VERTICAL WIND SHEAR (VWS), VERY WARM (29-30
C) SEA SURFACE TEMPERATURES, HIGH OCEAN HEAT CONTENT (OHC)
EXCEEDING 110 KJ PER CM3, AND STRONG RADIAL OUTFLOW ALOFT.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA SUPPLEMENTED BY
OBJECTIVE BEST TRACK

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) EXTENDING FROM SOUTH OF KYUSHU EASTWARD
INTO THE NORTHERN PACIFIC

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T6.5 - 127 KTS
   KNES: T6.5 - 127 KTS
   CIMSS SATCON: 116 KTS AT 031200Z
   CIMSS ADT: 129 KTS AT 031200Z
   CIMSS AIDT: 122 KTS AT 031200Z
   CIMSS D-PRINT: 124 KTS AT 031200Z

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: TYPHOON (TY) 09W (BAVI) HAS UNDERGONE EXTREME
RAPID INTENSIFICATION FROM 60 KTS TO 125 KTS OVER THE PAST 24
HOURS. THE SYSTEM HAS CONTINUED ON A NEARLY WESTWARD TRACK UNDER
THE STEERING INFLUENCE OF AN EXTENSION OF THE STR CENTERED TO THE
NORTHWEST OVER THE PAST 6 HOURS. A WEAKENING IN THE STEERING RIDGE
AS A LONGWAVE TROUGH TRANSITS EASTWARD WELL TO THE NORTH OF TY 09W
HAS SLOWED THE TRACK SPEED, WHICH IS EXPECTED TO REMAIN BELOW 10
KTS THROUGH TAU 36. THE CPA TO SAIPAN AND ROTA REMAINS SIMILAR TO
THE PREVIOUS FORECAST, EXPECTED AROUND 052100Z. THE ORIENTATION OF
THE STR CURRENTLY ANCHORED SOUTH OF KYUSHU AND ITS SLOW
NORTHWESTWARD MIGRATION OVER THE NEXT 120 HOURS WILL RESULT IN A
PRIMARILY WESTWARD COMPONENT TO THE TRACK THROUGH TAU 24. AFTER TAU
24, THE TRACK TURNS WEST-NORTHWESTWARD IN THIS STEERING ENVIRONMENT
FOR THE REMAINDER OF THE FORECAST PERIOD. RAPID INTENSIFICATION IS
FORECAST TO CONTINUE FOR THE NEXT 12 HOURS BEFORE LEVELING OFF AT A
PEAK OF 150 KTS AT TAU 24. AFTER TAU 36, VWS IS EXPECTED TO
STEADILY INCREASE TO 20 KTS AT TAU 60 AND 30-35 KNOTS BY TAU 120,
INITIATING A GRADUAL WEAKENING TREND. THE POSSIBILITY OF AN EYEWALL
REPLACEMENT CYCLE (ERC) REMAINS LIKELY, AS SUGGESTED BY HAFS-A,
WHICH INTRODUCES SOME UNCERTAINTY IN THE TIMING AND MAGNITUDE OF
THE PEAK INTENSITY. IN THE EVENT OF AN ERC, THE WIND FIELD IS
EXPECTED TO EXPAND AND FURTHER LIMIT INTENSIFICATION. 

MODEL DISCUSSION: MODEL TRACK GUIDANCE REMAINS IN A TIGHT ENVELOPE
THROUGH TAU 60, WITH THE EXCEPTION OF NAVGEM, WHICH SUGGESTS A
TRACK SOUTH OF ROTA. THE REMAINDER OF GUIDANCE HAS A CROSS-TRACK
SPREAD OF 55 NM AT TAU 60, JUST AFTER THE CENTER OF TY 09W IS
EXPECTED TO PASS BY THE MARIANA ISLANDS. THE TRACK GUIDANCE
MAINTAINS GOOD AGREEMENT AFTER TAU 60 AS WELL, WITH A CROSS-TRACK
SPREAD OF 75 NM AND AN ALONG-TRACK SPREAD OF 80 NM AT TAU 120. THE
JTWC TRACK FORECAST IS PLACED NEAR THE MULTI-MODEL CONSENSUS WITH
HIGH CONFIDENCE THROUGHOUT THE FORECAST PERIOD. MODEL INTENSITY
GUIDANCE CONTINUES TO SUPPORT THE RAPID INTENSIFICATION SCENARIO IN
THE SHORT TERM, THEN VARYING DEGREES OF GRADUAL WEAKENING THROUGH
THE REMAINDER OF THE FORECAST PERIOD, OWING TO THE UNCERTAINTY
ABOUT A POTENTIAL ERC. THE JTWC INTENSITY FORECAST IS PLACED ON THE
HIGHER END OF THE GUIDANCE ENVELOPE WITH MEDIUM CONFIDENCE
THROUGHOUT THE FORECAST PERIOD IN ANTICIPATION OF CONTINUED RAPID
INTENSIFICATION.

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