Tokyo in the Cone
Posted by JAC on 9/16/2009, 6:46 am











12 HOUR SUMMARY AND ANALYSIS.
      A. SUPER TYPHOON (STY) 15W (CHOI-WAN), LOCATED APPROXIMATELY
250 NM NORTH-NORTHWEST OF SAIPAN, HAS TRACKED WEST-NORTHWESTWARD AT
09 KNOTS OVER THE LAST 06 HOURS. RECENT ANIMATED MULTISPECTRAL
SATELLITE IMAGERY SHOWS AN IMPRESSIVE SYSTEM WITH DEEP CONVECTIVE
BANDING WRAPPING INTO A CENTER WITH A WELL DEFINED EYE. INTENSITY IS
BASED ON ESTIMATES FROM PGTW, KNES AND RJTD. STY 15W HAS TRACKED
ALONG THE SOUTHWESTERN PERIPHERY OF A MID-LEVEL SUBTROPICAL RIDGE
(STR) THAT EXTENDS FROM NORTHEAST OF STY 15W INTO THE VICINITY OF
IWO TO. TRACK SPEEDS HAVE REMAINED FAIRLY CONSISTENT OVER THE PAST
12 HOURS, RANGING FROM 08 TO 10 KNOTS. AN TROPICAL UPPER
TROPOSPHERIC TROUGH (TUTT) TO THE NORTHEAST HAS CONTINUED TO PROVIDE
GOOD EASTWARD OUTFLOW, IN ADDITION TO AN UPPER LEVEL POINT SOURCE
ANTICYCLONE OVER STY 15W THAT HAS BEEN PROVIDING STRONG RADIAL
OUTFLOW OVER THE PAST 24 HOURS. THE MULTIPLE OUTFLOW MECHANISMS IN
CONCERT WITH HIGH VALUES OF OCEAN HEAT CONTENT (OHC) AND SEA SURFACE
TEMPERATURES (SST) HAVE ALLOWED FOR STY 15W TO INTENSIFY FURTHER
OVER THE PAST 12 HOURS.
3. FORECAST REASONING.
   A. THE FORECAST PHILOSOPHY HAS CHANGED SLIGHTLY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE, WITH TRACK SPEED INCREASING
AFTER THE SYSTEM RECURVES TO THE NORTHEAST AS THE GRADIENT BETWEEN
THE STR AND AN APPROACHING MID-LATITUDE TROUGH IS FORECASTED TO BE
GREATER THAN PREVIOUSLY THOUGHT.
   B. STY CHOI-WAN WILL BEGIN TO SLOWLY TRACK MORE NORTHWESTWARD
THROUGH TAU 48 UNDER THE INFLUENCE OF THE STR DESCRIBED IN PARA 2.A.
THE SYSTEM WILL SLOWLY INTENSIFY OVER THE NEXT 12 TO 24 HOURS AND
THEN MAINTAIN THE SUPER TYPHOON INTENSITY THROUGH TAU 48 WITH
MULTIPLE UPPER LEVEL OUTFLOW CHANNELS SUPPORTING THE STRONG INFLOW
OVER REGIONS OF HIGH OHC AND SST VALUES. BY TAU 36, STY 15W WILL
REACH THE WESTERN EXTENT OF THE STR AND BEGIN TO TRACK MORE
NORTHWARD AROUND THE RIDGE AXIS. BY TAU 48 STY 15W WILL BEGIN TO
RECURVE NORTHEASTWARD.
    C. BEYOND TAU 72, CHOI-WAN WILL MAINTAIN A NORTHEASTWARD TRACK
AHEAD OF AN APPROACHING MID-LATITUDE TROUGH, WITH A STEADY INCREASE
IN TRACK SPEED THROUGH TAU 120. THE SYSTEM WILL BEGIN EXTRA-TROPICAL
TRANSITION AROUND TAU 96 AS IT INTERACTS WITH THE APPROACHING MID-
LATITUDE TROUGH. THE NUMERICAL MODELS ARE IN FAIR AGREEMENT WITH A
MODERATE TRACK SPREAD DURING THE RECURVATURE, WITH EGRR AS THE
WESTERN OUTLIER (REACHING WESTERN EXTENT AT 137E) AND THE MAIN
GROUPING OF MODELS REACHING 140E. THE MODELS ARE IN GOOD AGREEMENT
FOR TRACK AFTER TAU 48 ALONG THE NORTHWESTERN EXTENT OF THE STR.
THERE IS A LARGE MODEL SPREAD WITH REGARDS TO ALONG-TRACK SPEED
AFTER RECURVATURE WITH THIS FORECAST FOLLOWING CLOSE TO CONSENSUS.//
NNNN
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Super Typhoon Choi-Wan (ADT at Cat5) - JAC, 9/15/2009, 7:38 am
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