WDPN31 PGTW 041500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 09W (BAVI) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.7N 150.2E
   INITIAL INTENSITY: 140 KTS
   GEOGRAPHIC REFERENCE: 315 NM EAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
POWERFUL SUPER TYPHOON APPROACHING THE MARIANA ISLANDS. THE CENTRAL
DENSE OVERCAST AND EYE HAVE DEGRADED IN THE PAST SIX HOURS, WITH
WARMING CONVECTIVE CLOUD TOP TEMPERATURES AND A SLIGHTLY COOLER
EYE. THE UPPER-LEVEL OUTFLOW REMAINS ROBUST AND RADIAL. A 040806Z
WSF-M MWI PASS REVEALS A VERY THICK INNER CORE AND A LESS CIRCULAR
UPPER-LEVEL EYE. THE 37 GHZ IMAGE NOTABLY DEPICTS MULTIPLE,
INCOMPLETE LOWER-LEVEL RINGS SURROUNDING THE EYE, WHICH IS
INDICATIVE OF A PARTIAL EYEWALL REPLACEMENT CYCLE (ERC). THIS
OBSERVATION IS SUPPORTED BY THE MPERC ALGORITHM FROM CIMSS, WHICH
GIVES A 68 PERCENT PROBABILITY OF ERC ONSET. THE ENVIRONMENT
CONTINUES TO BE HIGHLY FAVORABLE FOR MAINTAINING A HIGH-END STORM,
CHARACTERIZED BY LOW VERTICAL WIND SHEAR (VWS), HIGH OCEAN HEAT
CONTENT EXCEEDING 125 KJ PER SQUARE CM, AND ABUNDANT DEEP-LAYER
MOISTURE. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE
BASED ON THE WELL-DEFINED EYE IN THE EIR IMAGERY. THE INITIAL
INTENSITY IS LOWERED TO 140 KTS WITH MEDIUM CONFIDENCE BASED ON THE
DEGRADED SATELLITE APPEARANCE BUT IS STILL ALIGNED WITH THE
UNANIMOUS T7.0 DVORAK FIXES FROM PGTW, KNES, RJTD, AND RCTP AND THE
OBJECTIVE ESTIMATES FROM CIMSS RANGING FROM 138 KTS TO 145 KTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: EASTERN EXTENSION OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED NEAR THE RYUKYU ISLANDS

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   RJTD: T7.0 - 140 KTS 
   RCTP: T7.0 - 140 KTS 
   KNES: T7.0 - 140 KTS 
   CIMSS SATCON: 141 KTS AT 040600Z
   CIMSS ADT: 140 KTS AT 041200Z
   CIMSS AIDT: 138 KTS AT 041200Z
   CIMSS D-MINT: 145 KTS AT 040807Z
   CIMSS D-PRINT: 145 KTS AT 041200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 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: THE FORWARD MOTION OF SUPER TYPHOON (STY) 09W
HAS VEERED SLIGHTLY NORTH OF DUE WEST. THE SYSTEM WILL COMMENCE A
WEST-NORTHWESTWARD TRAJECTORY THROUGH THE ENTIRETY OF THE FORECAST
PERIOD, DRIVEN BY A DEEP-LAYER STR TO THE NORTH. AS STY BAVI
ESCAPES THE GRASP OF A NEAR-EQUATORIAL RIDGE, IT WILL GAIN SPEED
AND REACH 12-15 KTS BY TAU 48. THE NEAR-TERM INTENSITY FORECAST HAS
BECOME MORE COMPLEX. THE ENVIRONMENT WILL BECOME EVEN MORE
FAVORABLE BETWEEN TAU 12 AND TAU 36 BECAUSE AN UPPER-LEVEL RIDGE
WILL BUILD EASTWARD FROM THE RYUKYU ISLANDS AND SIGNIFICANTLY
ENHANCE UPPER-LEVEL DIVERGENCE ON THE WESTERN PERIPHERY OF THE
VORTEX. THE COMPLICATION WILL COME FROM THE PARTIAL ERC PRESENTED
IN THE AFOREMENTIONED MICROWAVE PASS, WHICH IS A TRANSIENT,
UNSTABLE PROCESS, AND TWO POSSIBLE OUTCOMES ARISE. EITHER THE
PARTIAL OUTER BAND WILL SUCCESSFULLY WRAP AROUND THE CENTER AND
LEAD TO A COLLAPSE OF THE INNER EYE, OR THE INNER CORE WILL HOLD
UNTIL THE OUTER RING DISSIPATES. BOTH SCENARIOS WILL LEAD TO
WEAKENING, WHICH IS REFLECTED IN THE FORECAST AT TAU 12. THE
PROCESS WILL COMPLETE IN THE NEXT 12-24 HOURS, AND
RE-INTENSIFICATION WILL COMMENCE THEREAFTER. GIVEN THE EXCEPTIONAL
UPSTREAM ENVIRONMENT AND PAST OVERPERFORMANCE OF BAVI'S
INTENSIFICATION PHASE IN THE PAST FEW DAYS, THE FORECAST CALLS FOR
A NEW PEAK OF 150 KTS AT TAU 48. AN EVEN HIGHER PEAK CLOSER TO 160
KTS IS NOT OUT OF THE QUESTION. SLOW TO GRADUAL WEAKENING WILL
OCCUR TOWARDS THE LATTER PART OF THE FORECAST PERIOD DUE TO
INCREASING VWS. STY 09W WILL GRADUALLY EXPAND IN SIZE, BECOMING AN
EXTREMELY MASSIVE CIRCULATION WITH GALE-FORCE WINDS EXTENDING OUT
TO 300 NM FROM THE CENTER BY TAU 120. IMPACTS WILL EXTEND FAR FROM
THE CENTER.

MODEL DISCUSSION: WHILE THE AVAILABLE GUIDANCE REMAINS IN GOOD
AGREEMENT THROUGH TAU 96, THE HAFS-A, HWRF, AND GFS MODELS HAVE
SHIFTED POLEWARD, WHILE THE AI MODELS, ECMWF, GALWEM, AND NAVGEM
HAVE CHANGED LITTLE. THEREFORE, THE JTWC FORECAST TRACK HAS BEEN
NUDGED SLIGHTLY POLEWARD AND TAKES THE CENTER BETWEEN ROTA AND
TINIAN WITH MEDIUM CONFIDENCE. THE GUIDANCE ENVELOPE INCREASES
SIGNIFICANTLY AT TAU 120, WITH NAVGEM AND HAFS-A OPTING TO TURN THE
SYSTEM MORE NORTHWARD AND HWRF AND UKMET GOING WITH A MORE WESTWARD
MOTION. THE TAU 120 FORECAST POINT IS PLACED IN THE TIGHT GROUPING
OF TRACKERS NEAR THE MIDDLE OF THE SPREAD AND IS CLOSEST TO THE
ECMWF, GFS, JGSM, AND AI MODELS. ALL OF THE RELIABLE INTENSITY AIDS
DEPICT WEAKENING FOR THE FIRST 12 HOURS. THE COAMPS-TC AND THE
EXPERIMENTAL GOOGLE DEEPMIND MODELS SLIGHTLY RECOVER INTENSITY
AFTER TAU 24. HAFS-A IS THE MOST AGGRESSIVE, WITH THE INTERPOLATED
AID PEAKING STY BAVI AT 155 KTS AT TAU 60. MORE NOTABLY, A PEAK OF
160-165 KTS IS PREDICTED BY THE NONINTERPOLATED VERSION OF HAFS-A
AT TAU 60. THE JTWC INTENSITY FORECAST IS SET AT THE HIGHER END OF
THE MODEL SOLUTIONS BUT BELOW HAFS-A WITH MEDIUM CONFIDENCE.

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