WDPN31 PGTW 040900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 09W (BAVI) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.5N 150.8E
   INITIAL INTENSITY: 145 KTS
   GEOGRAPHIC REFERENCE: 352 NM EAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 50 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN
IMPROVEMENT IN THE CONVECTIVE STRUCTURE OF SUPER TYPHOON 09W. THE
CANOPY OF THE CENTRAL DENSE OVERCAST HAS BECOME MORE SYMMETRICAL
AND SMOOTHER, AND CLOUD TOP TEMPERATURES HAVE TRENDED COOLER. THE
EYE HAS CLEARED OUT, AND THE UPPER-LEVEL OUTFLOW HAS EXPANDED.
THESE INDICATORS POINT TO CONTINUED INTENSIFICATION. A 040252Z
AMSR-2 PASS SHOWS A VERY STRONG INNER CORE WITH A RING OF WEAKER
CONVECTION SURROUNDING THE EYEWALL. WHILE IT IS INCONCLUSIVE THAT
AN EYEWALL REPLACEMENT CYCLE (ERC) HAS BEGUN, THE CIMSS MPERC
ALGORITHM HAS LATCHED ON, ESTIMATING A 64 PERCENT PROBABILITY OF
ERC ONSET. THE ENVIRONMENT IS HIGHLY SUPPORTIVE OF A HIGH-END
STORM, CHARACTERIZED BY LOW VERTICAL WIND SHEAR, HIGH OCEAN HEAT
CONTENT (OHC) APPROACHING 150 KJ PER SQUARE CM, AND ABUNDANT
DEEP-LAYER MOISTURE. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE CLEAR EYE MEASURING 18 NM IN DIAMETER. THE
INITIAL INTENSITY WAS RAISED TO 145 KTS WITH MEDIUM CONFIDENCE
BASED ON THE IMPROVED CONVECTIVE SIGNATURE AND IS CLOSE TO THE
UNANIMOUS T7.0 FROM PGTW, KNES, RJTD, AND RCTP AND THE CIMSS
OBJECTIVE ESTIMATES RANGING FROM 140 KTS TO 145 KTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: EASTERN EXTENSION OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED EAST OF 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 040600Z
   CIMSS AIDT: 142 KTS AT 040600Z
   CIMSS D-MINT: 145 KTS AT 040607Z
   CIMSS D-PRINT: 143 KTS AT 040600Z

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: STY 09W IS PRIMARILY BEING STEERED DUE WEST BY
A DEEP-LAYER STR TO THE NORTH. THIS NEW MOTION REPRESENTS THE END
OF THE WEST-SOUTHWESTWARD MOVEMENT IN THE PAST 24 HOURS. THE
FORECAST CALLS FOR A TURN TOWARDS THE WEST-NORTHWEST AND A FASTER
RATE OF MOTION WITHIN THE NEXT 12-24 HOURS AS THE INFLUENCE OF A
NEAR-EQUATORIAL RIDGE OVER THE SOLOMON ISLANDS DIMINISHES AND A
STRONGER RIDGE BUILDS NORTHEAST OF THE VORTEX. THE MOTION WILL
PERSIST THROUGH THE END OF THE PERIOD. THE AVAILABLE MICROWAVE
IMAGERY AND MPERC SUGGEST THAT ERC WILL COMMENCE IMMINENTLY, IF NOT
ALREADY UNDERWAY. THE ERC WILL LEAD TO WEAKENING DURING THE FIRST
24 HOURS. ONCE ERC COMPLETES, STY BAVI WILL UNDERGO ANOTHER ROUND
OF INTENSIFICATION TO AT LEAST 150 KNOTS AS IT PASSES THE MARIANA
ISLANDS. IT IS CHALLENGING TO FORECAST THE AMOUNT OF WEAKENING DUE
TO ERC AND THE TIMING OF ERC COMPLETION, SO QUITE A BIT OF
UNCERTAINTY IN THE INTENSITY FORECAST EXISTS FOR THE FIRST 48
HOURS. THE ENVIRONMENT WILL REMAIN HIGHLY SUPPORTIVE OF THE EXTREME
INTENSITY. IN FACT, AS THE CIRCULATION APPROACHES THE MARIANA
ISLANDS, AN UPPER-LEVEL RIDGE WILL BUILD JUST SOUTH OF HONSHU AND
SIGNIFICANTLY INCREASE WESTWARD OUTFLOW ALOFT BEGINNING AT TAU 24.
STY BAVI WILL INTENSIFY AS A RESULT OF THE ENHANCED DIVERGENCE
ALOFT IF ERC CAN PROMPTLY COMPLETE. THE STORM WILL GROW VERY LARGE
IN SIZE AS A RESULT OF EYEWALL REPLACEMENT AND INTERNAL DYNAMICS,
SO IMPACTS WILL OCCUR FAR FROM THE CENTER.

MODEL DISCUSSION: MODELS ARE IN TIGHT AGREEMENT FOR THE FIRST 96
HOURS WITH AN ALONG-TRACK SPREAD OF 50 NM AND A CROSS-TRACK SPREAD
OF 100 NM AT TAU 96. THE TIGHT GROUPING OF MODELS SHIFTED SOUTHWARD
IN THE PAST FEW CYCLES BUT HAS STABILIZED. THE JTWC FORECAST TRACK
IS VERY SIMILAR TO THE PREVIOUS FORECAST AND IS PLACED CLOSE TO THE
MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE, TAKING THE CENTER OF
THE STY VERY CLOSE TO ROTA. THE INTENSITY GUIDANCE IS MORE MIXED
BUT GENERALLY SHOWS A CONSISTENT PHILOSOPHY. THE COAMPS-TC, HAFS-A,
AND EXPERIMENTAL GOOGLE DEEPMIND MODELS DEPICT 5-10 KTS OF
WEAKENING IN THE FIRST 24 HOURS. HAFS-A AND DEEPMIND BOTH SHOW
VARYING DEGREES OF INTENSIFICATION THEREAFTER, WITH HAFS-A
AGGRESSIVELY DEPICTING A RESURGENCE TO A PEAK OF 160 KTS AT TAU 48.
THE JTWC INTENSITY FORECAST LEANS INTO THIS SCENARIO AND CALLS FOR
A 150 KT PEAK. GIVEN THE EXCEPTIONAL ENVIRONMENT THROUGH WHICH STY
09W WILL MOVE AND THE STORM'S OVERPERFORMANCE OVER THE PAST TWO
DAYS, HIGHER INTENSITIES THAN DEPICTED IN THE FORECAST ARE NOT
OUTSIDE OF THE REALM OF POSSIBILITY. DUE TO UNCERTAINTIES POSED BY
ERC, THE INTENSITY FORECAST IS SET WITH LOW CONFIDENCE THROUGH TAU
72 AND MEDIUM CONFIDENCE FROM TAU 72 TO TAU 120.

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