WDPN31 PGTW 020300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (BAVI) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.9N 160.2E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 912 NM EAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 09W CONTINUES TO SLOWLY CONSOLIDATE BUT FACES
SOME HINDRANCE DUE TO 10-15 KNOTS OF SOUTHEASTERLY SHEAR. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SMALL CDO FEATURE
WHICH HAS BEGUN TO WEAKEN AND ELONGATE OVER THE LAST FEW HOURS,
ALLOWING FOR THE SOUTHEASTERN PERIPHERY OF THE LOW LEVEL
CIRCULATION CENTER (LLCC) TO BECOME EVIDENT ALONG THE SOUTHEASTERN
EDGE OF THE CDO. ELSEWHERE, WELL-DEFINED BANDS OF MODERATE
CONVECTION CONTINUE TO WRAP INTO THE OBSCURED LLCC. A 012230Z MHS
89GHZ MICROWAVE IMAGE DEPICTED A SMALL LLCC, WITH MODERATE
CONVECTION ALONG THE SOUTHWESTERN QUADRANT, WHILE THE SOUTHEASTERN,
UPSHEAR SECTOR, WAS DEVOID OF SIGNIFICANT CONVECTIVE ACTIVITY. THE
INITIAL POSITION IS ASSESSED WITH LOW CONFIDENCE, AS THE LLCC
REMAINS OBSCURED AND ONLY LOW-RESOLUTION MICROWAVE IMAGERY WAS
AVAILABLE TO ASSIST IN STRUCTURAL ANALYSIS. ADDITIONALLY, THE
AGENCY FIX POSITIONS ARE WIDELY SCATTERED, PROVIDING EVEN LESS
CONFIDENCE TO THE INITIAL POSITION. THE INITIAL INTENSITY IS
ASSESSED WITH LOW CONFIDENCE, AGAIN DUE TO A WIDE DISPERSAL IN THE
AGENCY INTENSITY ESTIMATES AS WELL AS THE OBJECTIVE ESTIMATES. THE
ENVIRONMENT REMAINS PRIMED TO SUPPORT RAPID INTENSIFICATION (RI),
WITH VERY WARM SSTS, HIGH OHC EXCEEDING 100 KJ PER CM3, STRONG
OUTFLOW INTO THE EASTERN, DIFFLUENT SIDE OF A TUTT TO THE NORTH AND
LOW (10-15 KTS) SOUTHEASTERLY VWS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN FLANK OF AN EXTENSION OF
THE SUBTROPICAL RIDGE (STR) SITUATED TO THE EAST OF THE SYSTEM. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T3.5 - 55 KTS
   PHFO: T3.0 - 45 KTS
   CIMSS ADT: 53 KTS AT 020020Z
   CIMSS AIDT: 42 KTS AT 020020Z
   CIMSS D-MINT: 46 KTS AT 012205Z
   CIMSS D-PRINT: 33 KTS AT 020020Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: MODERATE AMOUNT OF VERTICAL VORTEX TILT. 

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM (TS) 09W (BAVI) CONTINUES
TRACKING NORTHWESTWARD ALONG THE SOUTHWESTERN FLANK OF AN EXTENSION
OF THE STR POSITIONED TO THE EAST OF THE SYSTEM. OVER THE NEXT 24
HOURS, THIS AREA OF RIDGING WILL PUSH SOUTHEASTWARD WHILE STEADILY
WEAKENING, WHILE SIMULTANEOUSLY THE PRIMARY SUBTROPICAL RIDGE (STR)
CENTERED SOUTH OF KYUSHU WILL BUILD EASTWARD, TAKING OVER THE
PRIMARY STEERING INFLUENCE. THESE DYNAMIC STEERING PATTERN CHANGES
WILL LEAD TS 09W TO ASSUME A NEARLY WESTWARD TRAJECTORY BY TAU 24.
BY TAU 36, AN UPPER-LEVEL TROUGH WILL RAPID MOVE EASTWARD OFF THE
COAST OF JAPAN, MOVING QUICKLY INTO FAR NORTHERN PACIFIC, INDUCING
A WEAKNESS IN THE STR TO THE NORTH OF TS 09W. WHILE THE TROUGH WILL
NOT BE STRONG ENOUGH TO DRAW TS BAVI NORTHWARD, IT WILL BE STRONG
ENOUGH TO WEAKEN THE STEERING GRADIENT, RESULTING IN A FAIRLY SHARP
SLOW-DOWN IN THE FORWARD SPEED OF TS BAVI AFTER TAU 36. BEYOND TAU
72, THE SYSTEM SPEEDS UP MARGINALLY, AS A STR OVER THE RYUKYU
ISLANDS BEGINS TO EXTEND EASTWARD AND ASSUMES THE PRIMARY STEERING
ROLE. THE SYSTEM IS FORECAST TO PASS THROUGH THE NORTHERN MARIANAS
AROUND TAU 96. THE CPA TO GUAM HAS DECREASED BY APPROXIMATELY 30NM
SINCE THE PREVIOUS FORECAST AS THE AIDS PACKAGE HAS SHIFTED SHARPLY
SOUTHWARD. IN TERMS OF INTENSITY, THE SYSTEM IS EXPERIENCING SOME
NEGATIVE INFLUENCE FROM THE 10-15 KNOTS OF SOUTHEASTERN SHEAR,
INHIBITING RAPID CONSOLIDATION AND DELAYING THE ONSET OF RI.
HOWEVER, ALL AVAILABLE MODEL GUIDANCE DEPICTS A STEADY REDUCTION IN
SHEAR COMMENCING IMMINENTLY, AND HIGH-RESOLUTION MODEL FIELDS
DEPICT THE SYSTEM ACHIEVING AXISYMMETRIZATION WITHIN 12-24 HOURS.
ONCE THIS OCCURS, THE SYSTEM WILL COMMENCE RI, REACHING PEAK
INTENSITY OF AT LEAST 140 KNOTS WITHIN 72 HOURS. HAFS-A CONTINUES TO
DEPICT A PEAK INTENSITY EXCEEDING 150 KNOTS. AS EARLY AS TAU 72,
BUT THEN EXPLICITLY FORECASTS AN EYEWALL REPLACEMENT CYCLE (EWRC)
STARTING AROUND TAU 84 AND CONTINUING THROUGH PASSAGE TROUGH THE
NORTHERN MARIANAS. THE EXACT TIMING AND AMOUNT OF WEAKENING WROUGHT
BY THE EWRC IS YET TO BE DETERMINED WITH ANY FIDELITY, HOWEVER IT
CAN BE SAID THAT THE NORTHERN MARIANAS WILL EXPERIENCE AN IMPACT OF
A SIGNIFICANT SUPER TYPHOON WITHIN 96 HOURS.

MODEL DISCUSSION: THE OVERALL TRACK GUIDANCE PACKAGE HAS SHIFTED
SOUTHWARD AS WELL AS TIGHTENED UP SINCE THE PREVIOUS RUN.
CROSS-TRACK SPREAD AT TAU 72 HAS DECREASED TO 100NM, WHILE
CROSS-TRACK SPREAD AT TAU 120 HAS DECREASED TO 160NM AND THE WHOLE
PACKAGE HAS SHIFTED SOUTHWARD BY ROUGHLY 30NM. THE EXPERIMENTAL GDM
FGNI TRACKER AND THE UKMET ENSEMBLE MEAN LIE ON THE SOUTHERN EDGE
OF THE ENVELOPE, WHILE NAVGEM IS POSITIONED ON THE NORTHERN EDGE.
THE ARTIFICIAL INTELLIGENCE MODELS ARE ALL SITUATED IN THE SOUTHERN
HALF OF THE ENVELOPE, AND THE REMAINDER OF THE TRADITIONAL
DETERMINISTIC AND ENSEMBLE MEMBERS, EXCEPT FOR ECMWF, ARE LOCATED
IN THE NORTHERN HALF. THE JTWC FORECAST IS PLACED NEAR THE ECMWF
THROUGH MOST OF THE FORECAST PERIOD, WITH HIGH TO MEDIUM
CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD OVERALL AGREEMENT, THOUGH
UNCERTAINTY IN THE PEAK INTENSITY REMAINS LARGE. THE SHIPS GUIDANCE
PERSISTS ON THE LOW END OF THE SPECTRUM, PEAKING AT JUST 95 KNOTS,
WHILE THE COAMPS-TC ENSEMBLE MEAN AND HAFS-A ARE AT THE HIGH END,
BETWEEN 145-155 KNOTS. NEARLY ALL RI GUIDANCE CONTINUES TO TRIGGER
AND MULTIPLE RI PROBABILITIES ARE EXCEEDING 80-90 PERCENT, AN
UNPRECEDENTED VALUE, PROVIDING HIGH CONFIDENCE TO THE JTWC
FORECAST. 

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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