WDPN32 PGTW 221500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (TOKAGE) WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.7N 151.5E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 828 NM SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY INDICATES THE SYSTEM HAS TAKEN ON A SHRIMP-LIKE STRUCTURE, WITH AN ELONGATED AREA OF DEEP CONVECTION TO THE EAST OF THE LOW LEVEL CIRCULATION CENTER (LLCC), WHICH IS OBSCURED BY AN AREA OF SYMMETRICAL DEEP CONVECTION, DISTINCT FROM THE EASTERN BAND. THE MOST RECENT EIR IMAGERY SUGGEST THAT THE SYSTEM IS ATTEMPTING TO DEVELOP A BANDING EYE FEATURE, WITH SOME WEAK HOT TOWERS STARTING TO ROTATE AROUND THE ASSESSED CENTER. THERE HAS BEEN NO RECENT MICROWAVE IMAGERY BUT AN EARLIER SCATTEROMETER PASS FROM 220830Z PROVIDED A GOOD STARTING POINT FOR AN EXTRAPOLATION, LENDING MEDIUM CONFIDENCE TO THE INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED AT 45 KNOTS WITH HIGH CONFIDENCE BASED ON THE OVERALL OBJECTIVE AND SUBJECTIVE DVORAK FIXES AND THE EARLIER SCATTEROMETER PASS WHICH SHOWED A FEW 40 KNOT WINDS IN THE SOUTHEAST QUADRANT. THE SYSTEM HAS STARTED TO PICK UP SOME SPEED AS IT TRACKS MORE NORTHWARD ALONG THE WESTERN SIDE OF THE DEEP SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST. THE ENVIRONMENT IS VERY FAVORABLE FOR SUCH A HIGH LATITUDE SYSTEM, AS IT LIES BETWEEN A WEAKENING TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) TO THE WEST AND AN UPPER-LEVEL ANTICYCLONE JUST TO THE EAST, WHICH IS PRODUCING STRONG POLEWARD OUTFLOW OVER TOP OF THE SYSTEM AND LOW VWS. SSTS ARE QUITE WARM AS WELL, RUNNING ABOUT 29-30C.       

WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEST PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 47 KTS AT 221210Z
   
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE 
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS 
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: NONE

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

3. FORECAST REASONING. 

SIGNIFICANT FORECAST CHANGES. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE 
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
 
FORECAST DISCUSSION: TS 11W IS COMING TOGETHER NICELY UNDER FAVORABLE ENVIRONMENTAL CONDITIONS, DEVELOPING A POTENTIAL BANDING EYE AND TAKING ON THE CLASSIC SHRIMP SHAPE ASSOCIATED WITH DEVELOPING SYSTEMS. THE SYSTEM IS EXPECTED TO GRADUALLY TURN TO A NORTHWESTWARD TRACK OVER THE NEXT 12 HOURS AS THE STEERING RIDGE TO THE EAST SLIDES A BIT FURTHER TO THE SOUTH AND BUILDS. TS 11W WILL TRACK UP THE WESTERN SIDE OF THIS RIDGE, AND ROUND THE RIDGE AXIS BY TAU 48, THEN ACCELERATE NORTHEASTWARD ALONG THE NORTHWESTERN SIDE OF THE RIDGE THROUGH THE END OF THE FORECAST PERIOD. BY TAU 60 THE SYSTEM WILL BEGIN TO INTERACT WITH THE SOUTHERN END OF A WEAK BAROCLINIC ZONE AND MOVE UNDER THE SOUTHERN EDGE OF A STRONG 200MB JET MAX ASSOCIATED 500MB MINOR SHORTWAVE TROUGH AND BEGIN EXTRATROPICAL TRANSITION (ETT). ETT IS FORECAST TO COMPLETE NO LATER THAN TAU 96 AS THE SYSTEM RAPIDLY MOVES NORTHEAST TO THE EAST OF THE KURIL ISLANDS. TS 11W HAS ABOUT ANOTHER 12 HOURS UNDER THE VERY FAVORABLE UPPER-LEVEL FLOW PATTERN, BEFORE THE TUTT DISSIPATES TO THE WEST AND THE ANTICYCLONE WEAKENS AND MOVES DIRECTLY OVER THE SYSTEM. ONCE THIS OCCURS THE NET OUTFLOW WILL ACTUALLY DECREASE, PUTTING A CAP ON THE INTENSIFICATION. ONCE THE SYSTEM ROUNDS THE RIDGE AXIS AND STARTS TO BE IMPACTED BY DRAMATICALLY INCREASED SHEAR AND QUICKLY DECREASING SSTS, IT WILL START A RAPID WEAKENING TREND, BUT WILL ULTIMATELY COMPLETE ETT AS A GALE FORCE LOW.  

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE REMAINS IN GOOD AGREEMENT, THOUGH AVAILABLE TRACK AND INTENSITY GUIDANCE CONTINUES TO BE LIMITED DUE TO TECHNICAL ISSUES AT JTWC. HOWEVER, GLOBAL MODEL FIELDS AND THE ECENS AND GEFS MEMBERS REMAIN TIGHTLY FOCUSED IN A RELATIVELY NARROW CROSS-TRACK ENVELOPE. HOWEVER, AS IS NORMAL FOR RECURVING SYSTEMS, THERE IS A FAIR AMOUNT OF ALONG-TRACK SPREAD, PARTICULARLY AFTER THE SYSTEM ROUNDS THE RIDGE AXIS. THE JTWC FORECAST REMAINS CONSISTENT WITH THE PREVIOUS TRACK, WITH SLIGHTLY FASTER TRACK SPEEDS AFTER TAU 48, WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS MISSING FOR THE MOST PART, WITH ONLY THE COTC AND CTCX TRACKERS AVAILABLE. WITH ONLY TWO TRACKERS AVAILABLE, AND SHOWING A LARGE SPREAD BETWEEN 50 AND 75 KNOTS, THE JTWC FORECAST HAS INCREASED A BIT BASED ON THE RECENT TRENDS, BUT REMAINS BELOW THE HIGHEST MODEL ESTIMATES. CONFIDENCE IS LOW DUE TO THE LACK OF GUIDANCE. 

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