Uh-oh!
Posted by JAC on 9/16/2009, 10:32 am
12 HOUR SUMMARY AND ANALYSIS.
   A. RECENT ANIMATED MULTISPECTRAL IMAGERY SHOWS THAT MULTIPLE
SPIRAL BANDS HAVE WRAPPED TIGHTLY INTO THE CONSOLIDATED CENTER
OF TYPHOON CHOI-WAN TO FORM A BANDING EYE APPROXIMATELY 25 NM IN
DIAMATER. WATER VAPOR IMAGERY INDICATES THAT THE SYSTEM STILL HAS
VAST EQUATORWARD OUTFLOW AND A WELL-DEFINED POLEWARD OUTFLOW CHANNEL
INTO A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL TO THE EAST.
UPPER-LEVEL ANALYSIS REVEALS THAT THE TYPHOON HAS A FULLY-DEVELOPED
ANTICYCLONE ALOFT AND IS IN AN AREA OF MINIMAL VERTICAL WIND SHEAR.
OVER THE LAST 06 TO 12 HOURS, TY CHOI-WAN HAS SLOWED IN FORWARD
MOTION AND DIPPED TO THE SOUTHWEST AS THE MID-LATITUDE TROUGH
DIGGING EAST OF JAPAN HAS SERVED TO WEAKEN THE EASTERN SUBTROPICAL
RIDGE (STR) ANCHORED EAST OF THE DATE LINE AND CAUSE IT TO RETRACT
SOMEWHAT EAST. AT 131200Z THE MINAMITORISHIMA (RJAM) UPPER-AIR
SOUNDING STILL INDICATED THE PRESENCE OF EAST-NORTHEASTERLY WINDS
THROUGHOUT THE COLUMN, SIGNALING THAT AN EXTENSION OF THE STR WAS
STILL IN PLACE. HOWEVER, THE 140000Z RJAM SOUNDING SHOWS SOUTH-
WESTERLY WINDS AND THE SYSTEM HAS BEGUN TO TRACK NORTHWESTWARD UNDER
THE INFLUENCE OF THE BUILDING STR FURTHER TO THE NORTHWEST. THE
CURRENT POSITION IS BASED WITH HIGH CONFIDENCE ON THE MULTISPECTRAL
IMAGERY (AND ASSOCIATED 132330Z PGTW FIX) AND THE 131800Z POSITION
IS SUPPORTED BY THE 131614Z 36GHZ AMSRE MICROWAVE IMAGE. THE CURRENT
INTENSITY IS BASED ON THE PGTW DVORAK ESTIMATE OF T4.5.
3. FORECAST REASONING.
   A. THE FORECAST PHILOSOPHY HAS NOT CHANGED SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY CHOI-WAN WILL CONTINUE TO TRACK WEST-NORTHWESTWARD UNDER
THE INFLUENCE OF THE STEERING SUBTROPICAL RIDGE BUILDING EASTWARD
FROM THE NORTHWEST OF THE SYSTEM. BY TAU 72, THE SYSTEM WILL START
TO SLOW AS A DEEP MID-LATITUDE TROUGH TRANSITING THROUGH CHINA WILL
START TO BREAK DOWN THE STR ENOUGH TO INDUCE CHOI-WAN TO RECURVE
INTO THE MID-LATITUDES. THROUGH TAU 72, THE SYSTEM WILL CONTINUE TO
STEADILY INTENSIFY AS IT MOVES ALONG A FAVORABLE ENVIRONMENT
CHARACTERIZED BY EXCELLENT DUAL OUTFLOW AND WARM WATERS SUPPORTED BY
ROBUST OCEAN HEAT CONTENT VALUES..
    C. AFTER TAU 72, CHOI-WAN WILL START TO GRADUALLY RECURVE AS
THE MID-LATITUDE TROUGH MENTIONED IN PARA 3.B. CONTINUES TO WEAKEN
THE WESTERN STR. THE NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH
TAU 72, THOUGH THEY START TO SPREAD OUT BY TAU 96. THE EUROPEAN
SOLUTIONS OF ECMF AND EGRR DEPICT A SLOWER RECURVE WHILE THE AIDS
PRODUCED BY THE GFS, NOGAPS, AND GFDN MODELS ANTICIPATE A FASTER AND
SHARPER TRANSIT INTO THE MID-LATITUDES. THIS FORECAST FAVORS THE
EUROPEAN MODELS AND IS, THEREFORE, TO THE WEST OF THE JTWC
CONSENSUS.//NNNN
31
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Super Typhoon Choi-Wan (ADT at Cat5) - JAC, 9/15/2009, 7:38 am
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