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| #41819 (Received by flhurricane at: 11:05 AM 25.Aug.2005) TCDAT2 TROPICAL STORM KATRINA DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT THU AUG 25 2005 KATRINA HAS BECOME BETTER ORGANIZED BASED ON DOPPLER RADAR DATA AND SATELLITE IMAGERY. A FEW ISOLATED DOPPLER VELOCITIES AS HIGH AS 68 KT AT 9000-10000 FT HAVE OCCASIONALLY BEEN OBSERVED...BUT THE AVERAGE DOPPLER VELOCITIES OVER A 1-NMI STRETCH HAVE BEEN AROUND 55 KT...WHICH EQUATES TO ROUGHLY 50-KT SURFACE WINDS. THIS IS CONSISTENT WITH A BLEND OF SATELLITE INTENSITY ESTIMATES OF 45 KT FROM TAFB AND AFWA...AND 55 KT FROM SAB. A NOAA P-3 RECONNAISSANCE AIRCRAFT WITH SFMR CAPABILITY IS CURRENTLY INVESTIGATING KATRINA... AND A RECENT REPORT INDICATES THE PRESSURE IS NOW LOWER AT 990 MB. HOWEVER... THIS PRESSURE DROP HAS NOT YET TRANSLATED INTO A CORRESPONDING INCREASE IN WINDS. THE INITIAL MOTION ESTIMATE IS 270/5. 06Z AND 12Z UPPER-AIR DATA INDICATE THE SUBTROPICAL RIDGE TO THE NORTH OF KATRINA HAS CONTINUED TO SHIFT SLOWLY EASTWARD ALONG 32N LATITUDE. THIS HAS CREATED A DEEP-LAYER EASTERLY STEERING CURRENT...ALBEIT A WEAK ONE. THE NHC MODEL GUIDANCE IS IN FAIRLY GOOD AGREEMENT ON KATRINA MOVING GENERALLY WESTWARD ACROSS THE SOUTHERN FLORIDA PENINSULA FOR THE NEXT 48 HOURS OR SO. AFTER THAT...HOWEVER...THE MODELS CONTINUE TO DIVERGE SIGNIFICANTLY ON WHEN AND WHERE THE TURN TO THE NORTH TOWARD THE FLORIDA PANHANDLE OR NORTHWEST FLORIDA IS EXPECTED TO OCCUR. THE UKMET IS THE EASTERNMOST AND FASTEST MODEL AND BRINGS KATRINA ACROSS NORTHEAST FLORIDA...WHEREAS THE GFDL IS THE WESTERNMOST MODEL AND TAKES THE CYCLONE ACROSS THE WESTERN FLORIDA PANHANDLE. THE REST OF THE MODELS ARE EVENLY DISTRIBUTED BETWEEN THESE SOLUTIONS. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS TRACK AND IS CLOSE TO THE NHC MODEL CONSENSUS AFTER 48 HOURS. THE GFDL MODEL HAS BEEN CONSISTENTLY FORECASTING A SOUTHWESTWARD MOTION AROUND THE SOUTHERN END OF FLORIDA FOR THE PAST 24 HOURS. WHILE THIS TRACK IS CERTAINLY POSSIBLE TO SOME DEGREE...MY CURRENT THINKING IS THAT THE GFDL IS TAKING KATRINA TOO FAR SOUTH THROUGH THE FLORIDA KEYS AS A MAJOR HURRICANE. THE AFOREMENTIONED UPPER-AIR DATA INDICATE MID-LEVEL DRY AIR HAS GRADUALLY BEEN MOVING SOUTHWARD ACROSS THE FLORIDA PENINSULA AND KATRINA HAS BEEN MOVING ALONG THE NORTHERN EDGE OF A SHARP MOISTURE GRADIENT. THIS HAS RESULTED IN OCCASIONAL INTRUSIONS OF DRY AIR INTO THE INNER CORE AND HAS CAUSED THE CONVECTION TO WEAKEN. HOWEVER...OVER THE PAST FEW HOURS...RADAR DATA FROM MELBOURNE AND MIAMI INDICATE NUMEROUS SMALL BANDS OF CONVECTION ARE DEVELOPING IN THE LARGE DRY SLOT TO THE NORTH...AND A BANDING EYE FEATURE HAS BEEN TRYING TO DEVELOP. GIVEN THE SLOW FORWARD SPEED OVER THE VERY WARM GULFSTREAM AND THE FAVORABLE OUTFLOW PATTERN...KATRINA COULD STILL POSSIBLY REACH CATEGORY ONE HURRICANE STRENGTH PRIOR TO LANDFALL. KATRINA WILL WEAKEN AS IT MOVES OVER SOUTH FLORIDA...AND THEN RE-STRENGTHENING IS EXPECTED ONCE IT MOVES OVER THE WARM GULF OF MEXICO WHERE THE VERTICAL SHEAR IS FORECAST TO BE QUITE LOW. IT SHOULD BE NOTED THAT KATRINA IS NOT EXPECTED TO WEAKEN PRIOR TO LANDFALL...WHICH COULD BE IMPLIED BY THE OFFICIAL INTENSITY FORECAST. IN FACT...KATRINA WILL PROBABLY CONTINUE TO STRENGTHEN RIGHT UP UNTIL LANDFALL OCCURS IN THE FLORIDA PANHANDLE. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 25/1500Z 26.2N 79.3W 50 KT 12HR VT 26/0000Z 26.2N 80.0W 65 KT 24HR VT 26/1200Z 26.2N 81.0W 45 KT...INLAND 36HR VT 27/0000Z 26.3N 82.0W 40 KT 48HR VT 27/1200Z 26.7N 83.0W 50 KT 72HR VT 28/1200Z 28.1N 84.3W 70 KT 96HR VT 29/1200Z 30.5N 84.5W 60 KT...INLAND 120HR VT 30/1200Z 34.0N 82.0W 25 KT...DISSIPATING INLAND |
