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| #355351 (Received by flhurricane at: 4:58 AM 27.Jun.2010) TCDAT1 TROPICAL STORM ALEX DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL012010 400 AM CDT SUN JUN 27 2010 RATHER THAN BECOMING DISORGANIZED AFTER MOVING INLAND...RADAR AND SATELLITE DATA INDICATE THAT ALEX HAS ACTUALLY BECOME MUCH BETTER DEFINED. AN EYE FEATURE HAS BEEN NOTED IN BELIZE RADAR DATA AND SATELLITE IMAGERY INDICATES THAT CLOUD TOPS HAVE COOLED SIGNIFICANTLY WITH A NEARLY CLOSED RING OF -80C AND COLDER TOPS ENCIRCLING THE RADAR CENTER. THE UPPER-LEVEL OUTFLOW PATTERN REMAINS IMPRESSIVE AND ADDITIONAL CONVECTIVE BANDING FEATURES HAVE DEVELOPED IN ALL QUADRANTS. THE RADAR AND SATELLITE DEPICTIONS OF ALEX LOOKS MORE LIKE A HURRICANE THAN A LOW-END TROPICAL STORM. THE MOTION ESTIMATE IS 300/10. THE SHORT TERM MOTION IS THE ONLY THING STRAIGHT-FORWARD ABOUT THE FORECAST TRACK. ALL OF THE MODELS AGREE ON AN UPPER-LEVEL LOW CURRENTLY JUST EAST OF HUDSON BAY CANADA TO DIG SOUTHWARD AND CARVE OUT A DEEP TROUGH OVER MUCH OF THE EASTERN U.S. DURING THE NEXT 5 DAYS. AS THE TROUGH AMPLIFIES ...THE SUBTROPICAL RIDGE CURRENTLY SITUATED ACROSS FLORIDA AND THE NORTHERN GULF OF MEXICO ERODES IN THE 36-72 HOUR TIME FRAME LEAVING A LARGE WEAKNESS IN THE RIDGE OVER THE CENTRAL AND WESTERN GULF. THIS WEAK FLOW PATTERN IS EXPECTED TO CAUSE ALEX TO SLOW DOWN AND ALLOW THE CYCLONE TO GAIN SOME LATITUDE. AFTER THAT...HOWEVER...THE MODELS DIVERGE SIGNIFICANTLY WITH THE GFS AND CANADIAN MODELS TAKING ALEX NORTHWARD THROUGH THE WEAKNESS IN THE RIDGE TO THE TEXAS-LOUISIANA BORDER AREA...WHEREAS THE ECMWF...NOGAPS...GFDL... HWRF...UKMET...AND GFS-PARALLEL MODELS MOVE ALEX WESTWARD INTO NORTHEASTERN MEXICO. THE MAIN DIFFERENCE IN THE MODELS IS HOW THEY HANDLE THE MID-LATITUDE TROUGH-RIDGE PATTERN. THE GFS AND CANADIAN MODELS ARE MORE PROGRESSIVE AND LESS AMPLIFIED WITH THE FLOW PATTERN ACROSS THE NORTHERN U.S. DURING THE FORECAST PERIOD... WHEREAS THE OTHER MODELS PRODUCE A STRONGER...MORE HIGHLY AMPLIFIED ...AND SLOWER PATTERN. THE CURRENT PROGRESSIVE 5-WAVE NORTHERN HEMISPHERIC FLOW PATTERN WOULD TEND TO FAVOR THE THE GFS-CANADIAN SOLUTION...BUT AT LEAST ONE MORE MODEL CYCLE WILL BE REQUIRED TO CONFIRM THAT TREND. THE OFFICIAL FORECAST TRACK IS TO THE RIGHT OF AND SLOWER THAN THE PREVIOUS ADVISORY...AND IS SIMILAR TO THE CONSENSUS MODEL...TVCN. NOTE...IF THE RECENT NORTHWARD SHIFT IN THE MODELS CONTINUES...THEN ALEX COULD REMAIN OVER WATER FOR THE NEXT 5 DAYS RESULTING IN A VERY POWERFUL HURRICANE. BASED ON THE MUCH IMPROVED STRUCTURE OF ALEX WHILE IT IS HAS BEEN OVER LAND...THE INTENSITY FORECAST HAS BEEN ADJUSTED UPWARD FROM THE PREVIOUS ADVISORY. WITH VERTICAL SHEAR FORECAST TO BE 5 KT OR LESS DURING MOST OF THE FORECAST PERIOD AND SSTS OF 28C AND WARMER EXPECTED ALONG THE TRACK...THERE IS AT LEAST A MODERATE LIKELIHOOD THAT ALEX COULD BECOME A MAJOR HURRICANE. THE OFFICIAL INTENSITY FORECAST IS NEARLY IDENTICAL TO THE SHIPS AND DECAY-SHIPS INTENSITY MODELS...AND HIGHER THAN BOTH THE GFDL AND HWRF MODELS. FORECAST POSITIONS AND MAX WINDS INITIAL 27/0900Z 18.3N 89.4W 35 KT 12HR VT 27/1800Z 19.1N 90.6W 30 KT...INLAND 24HR VT 28/0600Z 20.2N 91.9W 40 KT...OVER WATER 36HR VT 28/1800Z 20.9N 92.8W 55 KT 48HR VT 29/0600Z 21.5N 93.6W 65 KT 72HR VT 30/0600Z 22.6N 95.5W 75 KT 96HR VT 01/0600Z 23.2N 97.4W 85 KT 120HR VT 02/0600Z 23.5N 99.7W 30 KT...INLAND $$ FORECASTER STEWART |
