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| #42101 (Received by flhurricane at: 11:08 AM 26.Aug.2005) TCDAT2 HURRICANE KATRINA DISCUSSION NUMBER 12 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT FRI AUG 26 2005 RECENT DATA FROM AN AIR FORCE RECON AIRCRAFT INDICATES KATRINA'S CENTRAL PRESSURE IS MUCH LOWER...NOW AT 971 MB. MAXIMUM 700 MB FLIGHT-LEVEL WINDS ARE 81 KT IN THE NORTHWEST QUADRANT...WHICH SUPPORTS AT LEAST 70 KT SURFACE WINDS. HOWEVER...THE AIRCRAFT HAS NOT SAMPLED THE WINDS IN THE EASTERN SEMICIRCLE WHERE NOAA/KEY WEST DOPPLER RADAR VELOCITY DATA INDICATES WINDS AS HIGH AS 91 KT AT AROUND 3000 FT...WHICH WOULD SUPPORT A SURFACE WIND ESTIMATE OF ABOUT 75 KT. THE INITIAL INTENSITY OF 70 KT MAY TURN OUT TO BE A LITTLE LOW. THE INITIAL MOTION ESTIMATE IS 265/6. RADAR DATA INDICATES KATRINA HAS CONTINUED TO MOVE SOUTH OF DUE WEST DURING THE PAST 6 HOURS. MOST OF THE NHC MODEL GUIDANCE INDICATES THE TRACK SHOULD FLATTEN OUT IN A MORE WESTWARD DIRECTION DURING THE NEXT 12 HOURS AS THE INFLUENCE OF AN INVERTED TROUGH OVER THE CARIBBEAN SEA DECREASES. THE MID-LEVEL SUBTROPICAL RIDGE TO THE NORTH AND NORTHWEST OF KATRINA IS FORECAST BY THE ALL GLOBAL AND REGIONAL MODELS TO GRADUALLY WEAKEN THROUGH THE FORECAST PERIOD AS A STRONG SHORTWAVE TROUGH OVER THE CENTRAL U.S. DIGS SOUTHEASTWARD TOWARD THE NORTHERN GULF OF MEXICO AND SOUTHEASTERN UNITED STATES. THE TIMING OF THE EROSION OF THE RIDGE AND AN INDUCED NORTHWARD MOTION OF KATRINA IS THE MAIN DIFFERENCE BETWEEN THE MODELS...WHICH HAS RESULTED IN A LARGE SPREAD AFTER 48 HOURS. THE NOGAPS AND GFDN MODELS HAVE MADE A LARGE JUMP TO THE WEST OVER LOUISIANA...WHEREAS THE MAJORITY OF THE NHC MODELS TAKE KATRINA INLAND OVER THE NORTHEAST GULF COAST. THE OFFICIAL FORECAST TRACK REMAINS IN THE RIGHT PORTION OF THE MODEL GUIDANCE ENVELOPE. STRENGTHENING TO A MAJOR HURRICANE IS EXPECTED. IN FACT...A RECENT DROPSONDE REPORT RECEIVED FROM THE RECONNAISSANCE AIRCRAFT INDICATES MAXIMUM WINDS ARE NOW UP TO 80 KT. SO...A SPECIAL ADVISORY WILL BE ISSUED SHORTLY TO UPDATE THE CURRENT AND FORECAST INTENSITIES. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 26/1500Z 25.1N 82.2W 70 KT 12HR VT 27/0000Z 25.2N 83.1W 75 KT 24HR VT 27/1200Z 25.5N 84.3W 80 KT 36HR VT 28/0000Z 26.2N 85.2W 85 KT 48HR VT 28/1200Z 27.1N 85.9W 90 KT 72HR VT 29/1200Z 29.5N 86.3W 100 KT 96HR VT 30/1200Z 34.5N 83.5W 35 KT...INLAND 120HR VT 31/1200Z 40.5N 77.0W 25 KT...DISSIPATING INLAND |
