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| #152449 (Received by flhurricane at: 4:34 PM 25.Sep.2007) TCDAT2 TROPICAL STORM KAREN DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122007 500 PM EDT TUE SEP 25 2007 KAREN CONTINUES TO SHOW SOME BANDING FEATURES AND A WELL-DEFINED CIRCULATION ON VISIBLE IMAGES...BUT ITS PRESENTATION ON INFRARED IMAGERY IS NOT VERY IMPRESSIVE. THE SYSTEM CONTINUES TO LACK MUCH IN THE WAY OF CENTRAL DEEP CONVECTION AND...IN FACT...THE OVERALL AMOUNT OF DEEP CONVECTION IS MINIMAL. DVORAK SATELLITE CLASSIFICATIONS ARE HOLDING AT 35 KT FROM BOTH TAFB AND SAB...SO THE ADVISORY INTENSITY IS UNCHANGED. THE UPPER-LEVEL OUTFLOW OVER THE NORTHERN SEMICIRCLE HAS BECOME A LITTLE BETTER ESTABLISHED AND...IF KAREN DEVELOPS SOME MORE CENTRAL CONVECTION...IT COULD STRENGTHEN SOME DURING THE NEXT COUPLE OF DAYS. HOWEVER...AN UPPER-TROPOSPHERIC TROUGH THAT THE GFS DEPICTS DEVELOPING IN THE VICINITY OF 55 W IN 2-3 DAYS SHOULD EVENTUALLY PRODUCE STRONG SOUTH-SOUTHWESTERLY SHEAR OVER KAREN. THEREFORE THE OFFICIAL INTENSITY FORECAST DOES NOT INDICATE THAT KAREN WILL BECOME A HURRICANE...AND SHOWS WEAKENING BEYOND DAY 3. THIS IS GENERALLY BELOW THE GFDL AND HWRF GUIDANCE BUT IN REASONABLE AGREEMENT WITH THE LATEST SHIPS OUTPUT. THE LGEM VERSION OF SHIPS...WHICH IS MORE RESPONSIVE TO CHANGES IN SHEAR OVER THE FORECAST PERIOD...SHOWS LESS INTENSIFICATION. INITIAL MOTION CONTINUES AT 285/13. A DEEP-LAYERED SUBTROPICAL RIDGE SITUATED TO THE NORTH OF THE CYCLONE SHOULD INDUCE A GENERAL WEST-NORTHWESTWARD MOTION DURING THE NEXT 24 TO 36 HOURS. BY MID- PERIOD...AN AMPLIFYING MID- TO UPPER-LEVEL TROUGH IS EXPECTED TO CREATE A PRONOUNCED WEAKNESS IN THE AFOREMENTIONED RIDGE. THIS FEATURE SHOULD CAUSE KAREN TO GRADUALLY TURN NORTHWESTWARD...AND BY THE END OF THE FORECAST PERIOD...NORTH-NORTHWESTWARD. THIS NHC FORECAST TRACK IS ESSENTIALLY A BLEND OF THE GFDL...GFS...AND U.K. MET OFFICE SOLUTIONS. FORECAST POSITIONS AND MAX WINDS INITIAL 25/2100Z 11.1N 39.9W 35 KT 12HR VT 26/0600Z 11.5N 41.9W 40 KT 24HR VT 26/1800Z 12.3N 44.6W 45 KT 36HR VT 27/0600Z 13.3N 47.1W 55 KT 48HR VT 27/1800Z 14.7N 48.8W 60 KT 72HR VT 28/1800Z 17.5N 51.0W 60 KT 96HR VT 29/1800Z 20.0N 52.5W 55 KT 120HR VT 30/1800Z 22.5N 53.5W 55 KT $$ FORECASTER ROBERTS/PASCH |
