ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM KATRINA DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT WED AUG 24 2005 SATELLITE IMAGERY...DOPPLER RADAR DATA FROM THE BAHAMAS AND MIAMI... AND THE LATEST RECONNAISSANCE WIND DATA INDICATE KATRINA HAS CONTINUED TO BECOME BETTER ORGANIZED THIS AFTERNOON. BANDING FEATURES HAVE INCREASED IN ALL QUADRANTS AND THE UPPER-LEVEL OUTFLOW HAS EXPANDED AND REMAINS QUITE SYMMETRICAL. THE INITIAL INTENSITY OF 40 KT IS A BLEND OF RECON WIND...38 KT FLIGHT-LEVEL WINDS...AND PRESSURE DATA...1002 MB OR ROUGHLY 43 KT...AND SATELLITE INTENSITY ESTIMATES OF 45 KT FROM TAFB AND AFWA. THE INITIAL POSITION ESTIMATE IS A LITTLE TO SOUTHWEST OF THE 1949Z RECON POSITION AND IS CLOSE TO THE CENTER OF THE LARGER-SCALE CIRCULATION BASED ON EXTRAPOLATION OF THE ZERO-ISODOP PATTERN NOTED IN THE NOAA/NWS MIAMI DOPPLER VELOCITY DATA. THE INITIAL MOTION ESTIMATE IS 325/08. THERE IS SOME UNCERTAINTY IN BOTH THE INITIAL MOTION AND THE CENTER POSITION. I HAVE TRIED TO BLEND THE POSITIONS FROM RECON...RADAR AND SATELLITE DATA. THE LAST RECON POSITION CAN BE SEEN AS A TIGHT LOW-LEVEL VORTEX MOVING OUT FROM UNDERNEATH THE DEEP CONVECTION IN THE EAST SEMICIRCLE. IT IS POSSIBLE THAT THAT VORTEX MAY END UP BEING A TRANSIENT FEATURE. IF IT TURNS OUT THAT THE CENTER DOES END UP FARTHER NORTH...THEN THE FORECAST TRACK WILL HAVE TO BE SHIFTED SLIGHTLY NORTHWARD ON THE NEXT ADVISORY. OTHER THAN THE UNCERTAINTY IN THE INITIAL POSITION ...THE REST OF THE FORECAST TRACK AND REASONING REMAINS UNCHANGED FROM PREVIOUS ADVISORIES. ALL OF THE NHC MODEL GUIDANCE AGREE ON THE SUBTROPICAL RIDGE TO THE NORTH OF KATRINA TO KEEP BUILDING SLOWLY EASTWARD...WHICH ULTIMATELY FORCES THE CYCLONE WESTWARD ACROSS SOUTH FLORIDA IN 36-48 HOURS...AND INTO THE EASTERN GULF OF MEXICO BY 72 HOURS. AFTER THAT...HOWEVER...THE MODELS DIFFER SIGNIFICANTLY ON WHERE AND WHEN KATRINA IS EXPECTED TO TURN NORTHWARD AND MAKE A SECOND LANDFALL ALONG THE NORTHEAST GULF COAST. THE GFDN IS THE WESTERNMOST MODEL AND TAKES THE CYCLONE TO NEW ORLEANS...WHEREAS THE GFS AND CANADIAN MODELS ARE THE EASTERNMOST MODELS AND TAKE KATRINA NORTHEASTWARD ACROSS THE NORTHERN FLORIDA PENINSULA. THE OFFICIAL TRACK IS NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE AND CLOSE TO THE MODEL CONSENSUS. WITH THE IMPROVED BANDING FEATURES...SYMMETRICAL UPPER-LEVEL OUTFLOW ...AND RELATIVELY WEAK SHEAR...AT LEAST STEADY INTENSIFICATION OF A NORMAL RATE OF 10 KT PER 12 HOURS UNTIL LANDFALL OCCURS SEEMS JUSTIFIED. THIS IS SIMILAR TO THE SHIPS INTENSITY MODEL...BUT MUCH LESS THAN THE NOW VERY BULLISH GFDL MODEL WHICH BRINGS KATRINA TO 111 KT JUST BEFORE LANDFALL. IT SHOULD BE POINTED OUT THAT WITH SSTS NEAR 31C AND A LOW SHEAR ENVIRONMENT...CONDITIONS ARE FAVORABLE FOR POSSIBLE RAPID INTENSIFICATION TO OCCUR BETWEEN NOW AND LANDFALL. THIS IS SUGGESTED BY THE SHIPS MODEL EXPERIMENTAL RAPID INTENSIFICATION OUTPUT...WHICH INDICATES A 57 PERCENT PROBABILITY OF THAT OCCURRING. THE ONLY INHIBITING FACTOR IS THE DRY AIR THAT SURROUNDS KATRINA AND HAS BEEN WORKING ITS WAY INTO THE INNER-CORE REGION AND ERODING THE DEEP CONVECTION. IF THE DRY AIR MIXES OUT WITHIN THE NEXT 12 HOURS...THEN INTENSITIES WOULD LIKELY BE HIGHER THAN THE OFFICIAL FORECAST IS INDICATING. OWING TO THE SLOW FORWARD SPEED...KATRINA HAS THE POTENTIAL TO PRODUCE A SIGNIFICANT HEAVY RAINFALL AND FLOODING EVENT ACROSS THE CENTRAL AND NORTHWEST BAHAMAS...AND EVENTUALLY ACROSS SOUTH FLORIDA. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 24/2100Z 25.6N 77.2W 40 KT 12HR VT 25/0600Z 25.9N 77.8W 50 KT 24HR VT 25/1800Z 26.1N 78.8W 60 KT 36HR VT 26/0600Z 26.2N 79.7W 70 KT 48HR VT 26/1800Z 26.3N 80.7W 50 KT...INLAND 72HR VT 27/1800Z 26.4N 83.0W 55 KT 96HR VT 28/1800Z 28.0N 85.0W 70 KT 120HR VT 29/1800Z 30.5N 85.0W 65 KT...INLAND $$ NNNN
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Page last modified: Wednesday, 24-Aug-2005 21:10:06 GMT