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#106250 (Received by flhurricane at: 10:55 AM 26.Aug.2006) TCDAT5 TROPICAL STORM ERNESTO DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL052006 1100 AM EDT SAT AUG 26 2006 THE LAST REPORT FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT AT ABOUT 09Z INDICATED A CENTRAL PRESSURE OF 997 MB AND MAXIMUM 850 MB FLIGHT-LEVEL WINDS OF 60 KT. MICROWAVE DATA FROM THE WINDSAT SATELLITE AND MORNING VISIBLE IMAGERY SHOWS THAT ERNESTO REMAINS PARTLY SHEARED WITH THE LOW-LEVEL CENTER NEAR THE WESTERN EDGE OF THE VERY STRONG CONVECTIVE MASS. THE INITIAL INTENSITY IS SET AT 45 KT IN AGREEMENT WITH SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB...AND THIS COULD BE A LITTLE CONSERVATIVE. THE INITIAL MOTION IS 285/12...A LITTLE SLOWER THAN BEFORE. OTHER THAN THAT...THE SYNOPTIC PATTERN...FORECAST REASONING...AND FORECAST TRACK FOR THE FIRST 72 HR ARE ESSENTIALLY UNCHANGED SINCE THE PREVIOUS PACKAGE. DURING THIS TIME...ERNESTO SHOULD MOVE WEST-NORTHWESTWARD NEAR JAMAICA...THE CAYMAN ISLANDS...AND WESTERN CUBA. THE FORECAST TRACK IS MORE PROBLEMATIC AFTER 72 HR. THE LARGE-SCALE MODELS AGREE THAT THE MID-LEVEL RIDGE OVER THE GULF OF MEXICO WILL WEAKEN AS A SHORTWAVE TROUGH DIGS SOUTHEASTWARD THROUGH THE MISSISSIPPI VALLEY. HOWEVER...THERE ARE DIFFERENCES IN HOW MUCH WEAKENING WILL OCCUR. THE ECMWF AND NOGAPS CALL FOR ERNESTO TO RECURVE OVER THE EASTERN GULF OF MEXICO...WHILE THE UKMET SHOWS ENOUGH RIDGE TO KEEP ERNESTO MOVING WEST-NORTHWESTWARD. THE GFS AND CANADIAN MODELS ARE IN BETWEEN...CALLING FOR SLOW MOTION OVER THE CENTRAL GULF. COMPLICATING MATTERS FURTHER IS A LACK OF RUN-TO-RUN CONSISTENCY. GIVEN THE UNCERTAINTY...THE FORECAST TRACK AFTER 72 HR CALLS FOR A SLOWER FORWARD SPEED...WITH A MORE NORTHWARD MOTION THAN IN THE PREVIOUS PACKAGE. OVERALL..THE NEW FORECAST TRACK IS IN BEST AGREEMENT WITH THE FSU SUPERENSEMBLE. THE LARGE-SCALE MODELS CONTINUE TO FORECAST THE DEVELOPMENT OF A LARGE UPPER-LEVEL ANTICYCLONE ALONG THE FORECAST TRACK...ALTHOUGH SO FAR THEY HAVE BEEN TOO FAST IN DOING SO. IF THE MODELS ARE CORRECT...THE CURRENT 15-20 KT OF WESTERLY SHEAR SHOULD DIMINISH DURING THE NEXT 12-24 HR AND ALLOW ERNESTO TO STRENGTHEN. THE INTENSITY FORECAST CALLS FOR SLOW STRENGTHENING DURING THE FIRST 36 HR...AND STEADY STRENGTHENING THEREAFTER. THE INTENSITY FORECAST CALLS FOR ERNESTO TO REACH 100 KT INTENSITY IN 120 HR...IN GOOD AGREEMENT WITH THE SHIPS AND GFDL MODELS...AND THE STORM COULD GET STRONGER THAN THAT. IT SHOULD BE NOTED THAT THE INTENSITY GUIDANCE...FOR AS OF YET UNDETERMINED REASONS...CALLS FOR LITTLE INTENSIFICATION AFTER 96 HR EVEN THOUGH THERE ARE NO OBVIOUS INHIBITING FACTORS. IN SUMMARY...ERNESTO COULD BECOME A POTENTIALLY DANGEROUS HURRICANE AS IT MOVES ACROSS THE NORTHWESTERN CARIBBEAN SEA AND THE GULF OF MEXICO. INTERESTS IN THESE AREAS SHOULD CLOSELY MONITOR THE PROGRESS OF THIS SYSTEM. FORECAST POSITIONS AND MAX WINDS INITIAL 26/1500Z 15.1N 71.2W 45 KT 12HR VT 27/0000Z 15.8N 73.0W 50 KT 24HR VT 27/1200Z 17.0N 75.5W 60 KT 36HR VT 28/0000Z 18.4N 78.1W 60 KT...OVER JAMAICA 48HR VT 28/1200Z 19.9N 80.5W 70 KT...OVER WATER 72HR VT 29/1200Z 22.5N 84.0W 80 KT...OVER WESTERN CUBA 96HR VT 30/1200Z 24.5N 87.0W 90 KT...OVER WATER 120HR VT 31/1200Z 27.0N 88.5W 100 KT |