WDPN31 PGTW 262100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (MINDULLE) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.4N 136.7E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 650 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 46 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
20W STRUGGLING THROUGH AN EYEWALL REPLACEMENT CYCLE (ERC) THAT
BEGAN NEAR 260700Z. TOPS ARE WARMING AND THERE ARE INDICATION OF
DRY AIR ENTRAINMENT OVER THE WESTERN SEMICIRCLE. A SERIES OF
MICROWAVE IMAGES ENDING WITH A 262116Z AMSR2 COLOR COMPOSITE
INDICATE THAT THE NEW EYEWALL IS DISCONTINUOUS, PARTICULARLY OVER
THE NORTHWEST QUADRANT.  SUBJECTIVE DVORAKS HAVE DROPPED
SUBSTANTIALLY BUT FINAL INTENSITIES ARE BEING HELD HIGHER DUE TO
CONSTRAINTS. THE JTWC ASSESSMENT IS BASED ON AUTOMATED ASSESSMENTS
FROM SATCON AND ADT.

INITIAL WIND RADII BASIS: 261232Z METOP-B ASCAT.

CURRENT STEERING MECHANISM: COMPETING STEERING FORCES: A BUILDING
ANTICYCLONE OVER THE MARIANAS IS NUDGING THE STORM POLEWARD WHILE
STRONG RIDGING BUIDLING AFROM AN ANTICYCLONE CENTERED OVER SHANGHAI
IS FORCING THE STORM EASTWARD WHILE IMPEDING POLEWARD MOVEMENT.  

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   RJTD: T7.0 - 140 KTS 
   RCTP: T6.0 - 115 KTS
   KNES: T6.5 - 127 KTS
   CIMSS SATCON: 107 KTS AT 261705Z
   CIMSS ADT: 107 KTS AT 261740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: THERE IS SOME SUPPRESSION OF OUTFLOW OVER THE
NORTHWESTERN QUADRANT. 

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: IT IS ALL FUN AND GAMES UNTIL THE TYPHOON
LOSES AN EYE. THE ERC COUPLED WITH SLOW MOVEMENT OF TY 20W HAS
ACTED TO SUPPRESS DEVELOPMENT OVER THE PAST 12 HOURS. TY 20W IS
ALMOST A VICTIM OF ITS OWN STRENGTH AS THE SEVERE WINDS ARE
CHURNING UP COLDER WATERS FROM BELOW AND SLOWING THE ERC. THE
LATEST FIX SHOWS THAT THE SYSTEM HAS BEGUN TO MOVE POLEWARD A
LITTLE AND BEGINNING TO TRACK AHEAD OF THE WAKE OF COOLER WATERS,
BUT BY THE TIME IT COMPLETES THE ERC AND MOVES AWAY FROM THE COOL
EDDY AND UPWELLING IT WILL BEGIN TRACKING THROUGH A REGION OF LOWER
OCEAN HEAT CONTENT AND INCREASING VERTICAL WIND SHEAR (VWS).
INTENSITY GUIDANCE INDICATES SOME RE-INTENSIFICATION BETWEEN TAU 24
AND 48 AS THE ERC COMPLETES AND THE STORM REMAINS SOUTH OF THE
TROPIC OF CANCER. NORTH OF THE 30TH LATITUDE, THE SYSTEM WILL MOVE
INTO A REGION OF MUCH GREATER VWS AND BEGIN INTERACTING WITH THE
MID-LATITUDE WESTERLIES, BEGINNING THE EXTRA-TROPICAL TRANSITION
PROCESS. 

MODEL DISCUSSION: BOTH ECMWF AND GFS HAVE BEEN WEAK ON TWO ISSUES
OVER THE PAST 48 HOURS: FIRST, BOTH FAILED TO PREDICT THE UPPER
LEVEL ANTICYCLONE AND ITS ASSOCIATED HIGH AMPLITUDE RIDGE THAT
FORMED OVER THE MARIANAS. PREVIOUSLY THEY SHOWED ONLY A BROAD AND
LAZY WESTWARD EXTENSION OF THE BONIN HIGH. THAT RIDGE IS NOW
BLOCKING ANY EASTWARD MOVEMENT AND PUSHING THE STORM POLEWARD.
SECOND, WHILE BOTH CAPTURED THE ANTICYCLONE SOUTH OF SHANGHAI,
NEITHER ESTIMATED THE EASTWARD EXTENT OF ITS ASSOCIATED RIDGE,
WHICH HAS BUILT OVER THE RYUKUS AND IS IMPEDING POLEWARD PROGRESS
OF THE SYSTEM. THE COMBINATION OF THE TWO FACTORS IS STALLING THE 
SYSTEM 
AND SLOWING THE ERC, CAPPING INTENSIFICATION OF 20W. 
ASIDE FROM THOSE WEAKNESSES, MODEL GUIDANCE HAS DONE AN OUTSTANDING
JOB CAPTURING THE NARRATIVE OF THE STORM AND IS DOING NOTHING BUT
GETTING TIGHTER WITH EACH SUCCESSIVE RUN. THERE IS INCREASING
CONFIDENCE THAT THE CENTER OF THE STORM WILL STAY WELL SEAWARD OF
THE KANTO PLAIN, ALTHOUGH ITS PROXIMITY WILL LIKELY INDUCE GALE TO
STORM FORCE NORTHEASTERLIES OFF-SHORE. THE INTENSITY GUIDANCE IS
NOW BEGINNING TO SHOW THE RESURGENCE IN THE 24 TO 48 HOUR PERIOD AS
THE SYSTEM COMPLETES ERC AND UNERGOES A MILD RE-INTENSIFICATION. 
THE GREATEST DIFFICULTY WITH GUIDANCE IS THE EXTENT OF WINDFILED
EXPANSION IN THE EXTENDED FORECAST AS THE SYSTEM STRETCHES AND
UNDERGOES EXTRA-TROPICAL TRANSITION, ALWAYS A DIFFICULT TASK.  THE
JTWC TRACK FORECAST STAYS STRAIGHT ON THE MULTI-MODEL CONSENSUS,
THE INTENSITY FORECAST RUNS A LITTLE ABOVE CONSENSUS DURING THE TAU
24-48 PERIOD, AND THE WINDFIELDS FOLLOW THE RVCN MODEL. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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