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| #355669 (Received by flhurricane at: 4:55 AM 28.Jun.2010) TCDAT1 TROPICAL STORM ALEX DISCUSSION NUMBER 11 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL012010 400 AM CDT MON JUN 28 2010 DEEP CONVECTION WITH CLOUD TOPS OF -80C TO -84C HAVE DEVELOPED NEAR AND AROUND THE CENTER OF ALEX DURING THE PAST FEW HOURS. AN AIR FORCE RESERVE UNIT AIRCRAFT AROUND 05Z FOUND THE CENTRAL PRESSURE TO STILL BE AROUND 991 MB...BUT FLIGHT-LEVEL WINDS HAD INCREASED TO 51 KT...EQUAL TO ABOUT 38 AT THE SURFACE. THE AIRCRAFT ALSO MEASURED AN SFMR SURFACE WIND OF 41 KT IN THE NORTHERN QUADRANT ON ITS OUTBOUND LEG. BASED ON THIS INFORMATION AND THE MARKED INCREASE IN CENTRAL DEEP CONVECTION SINCE THE RECON FIX...THE INITIAL INTENSITY IS SET AT 45 KT. THE INITIAL MOTION ESTIMATE IS 315/05 BASED ON RECON FIX DATA. COMPARED TO LAST NIGHT...THE MODELS ARE IN MUCH BETTER AGREEMENT ON THE EVOLUTION OF THE SYNOPTIC-SCALE FLOW PATTERN ACROSS THE U.S. AND THE GULF OF MEXICO. IN FACT...THE 500 MB HEIGHT AND WIND FIELDS ARE NEARLY IDENTICAL WITH THE STRENGTH AND PLACEMENT OF THE DEVELOPING TROUGH-RIDGE PATTERN THROUGH 72 HOURS. DESPITE THESE STRIKING SIMILARITIES...HOWEVER...THERE IS STILL CONSIDERABLE DIVERGENCE IN THE FORECAST TRACKS...ESPECIALLY AFTER 48 HOURS. FOR THE NEXT 2 DAYS OR SO...THE MODELS ARE IN GENERAL AGREEMENT ON A SLOW NORTHWESTWARD MOTION. AFTER THAT...THE GFS...GFS-PARALLEL... CMC...HWRF...AND GFDL MODEL KEEP ALEX ON A NORTHWESTWARD TRACK AND BRING THE CYCLONE INLAND ALONG THE LOWER OR CENTRAL TEXAS COAST. IN CONTRAST...THE ECMWF...UKMET...AND NOGAPS MODELS TAKE ALEX WESTWARD INTO THE NORTHEASTERN COAST OF MEXICO...WITH THE ECMWF HAVING THE MOST SOUTHERN TRACK OF THOSE MODELS. HOWEVER...THE ENTIRE NHC MODEL SUITE HAS SHIFTED NORTH AGAIN...ALONG WITH THE ECMWF MODEL. THE ONLY DIFFERENCE I CAN SEE BETWEEN THE MODELS IS THAT THE THE ECMWF...UKMET...AND ESPECIALLY NOGAPS DEPICT ALEX AS A SMALLER AND WEAKER CYCLONE THAN THE OTHER MODELS ARE FORECASTING. GIVEN THAT ALEX IS EXPECTED TO BE A RELATIVELY LARGE HURRICANE BY 72 HOURS... GREATER WEIGHT WAS PLACED ON THE OTHER MODEL SOLUTIONS... WHICH HAS RESULTED IN A NORTHWARD SHIFT OF THE FORECAST TRACK...BUT STILL REMAINS SOUTH OF THE NHC CONSENSUS MODEL..TVCN. THE NORMALLY ROBUST GFDL AND HWRF MODELS ARE STILL ONLY FORECASTING MODEST INTENSIFICATION OF ALEX...WHICH REMAINS SOMEWHAT PERPLEXING GIVEN THE VERY LOW VERTICAL SHEAR ENVIRONMENT AND IMPRESSIVE OUTFLOW ENVIRONMENT IN WHICH ALEX IS CURRENTLY IN AND IS FORECAST TO REMAIN EMBEDDED IN FOR THE NEXT SEVERAL DAYS. THE CURRENT CENTRAL PRESSURE IS MORE TYPICAL OF SYSTEM NEARING HURRICANE STRENGTH. GIVEN THAT THE SHEAR IS EXPECTED TO REMAIN QUITE LOW AND THE ATMOSPHERE IS FORECAST TO REMAIN VERY MOIST IN THE MID-LEVELS ...I SEE NO REASON WHY ALEX SHOULD NOT CONTINUE TO STRENGTHEN...AND POSSIBLY EVEN BECOME A MAJOR HURRICANE BEFORE LANDFALL. THE OFFICIAL INTENSITY FORECAST IS SLIGHTLY HIGHER THAN THE VERY RELIABLE LGEM MODEL...WHICH BRINGS ALEX UP TO 90 KT BY 72 HOURS. FORECAST POSITIONS AND MAX WINDS INITIAL 28/0900Z 19.7N 91.6W 45 KT 12HR VT 28/1800Z 20.3N 91.9W 55 KT 24HR VT 29/0600Z 21.4N 92.7W 65 KT 36HR VT 29/1800Z 22.4N 93.6W 75 KT 48HR VT 30/0600Z 23.3N 94.7W 85 KT 72HR VT 01/0600Z 24.6N 97.0W 95 KT 96HR VT 02/0600Z 25.6N 99.2W 40 KT...INLAND 120HR VT 03/0600Z 26.5N 101.0W 20 KT...DISSIPATING INLAND $$ FORECASTER STEWART |
