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| #9777 (Received by flhurricane at: 5:10 PM 23.Sep.2004) TCDAT4 TROPICAL STORM IVAN DISCUSSION NUMBER 71 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT THU SEP 23 2004 AFTER THE EARLIER A BURST OF CONVECTION...THUNDERSTORM ACTIVITY HAS DWINDLED AND THE WIND HAVE DECREASED ACCORDINGLY. THE INITIAL INTENSITY OF 40 KT AND A PRESSURE OF 1003 MB IS BASED ON THE LAST RECON REPORT AROUND 17Z. THE INITIAL MOTION ESTIMATE IS 310/07. THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST REASONING. IVAN SHOULD CONTINUE TO MOVE NORTHWESTWARD TO WEST-NORTHWESTWARD AND BE INLAND WITHIN THE NEXT 12 HOURS OVER SOUTHWESTERN LOUISIANA OR THE UPPER-TEXAS COAST. AFTERWARDS...RAPID WEAKENING WILL RESULT IN THE LOW-LEVEL CIRCULATION DECOUPLING FROM THE MID- AND UPPER-LEVEL CIRCULATIONS. THIS SHOULD ALLOW THE LOW-LEVEL CIRCULATION TO BE STEERED SLOWLY WEST AND THEN SOUTHWESTWARD BY A LARGE LOW-LEVEL RIDGE/HIGH THAT IS FORECAST TO BUILD EASTWARD OVER THE CENTRAL AND SOUTHERN PLAINS BEHIND A COLD FRONT. THE TRACK SCENARIO REMAINS CONSISTENT WITH THE SHALLOW BAM MODEL AND MOST OF THE GLOBAL MODELS. WHILE A FEW MODELS TAKE THE LOW-LEVEL CIRCULATION BACK OVER THE GULF OF MEXICO IN 36-48 HOURS...STRONG SOUTHWESTERLY UPPER-LEVEL WINDS OF MORE THAN 40 KT SHOULD PREVENT ANY REDEVELOPMENT FROM OCCURRING. WHILE IVAN IS NOT EXPECTED TO BE A PROLIFIC WIND PRODUCER...ITS SLOW FORWARD SPEED FOR THE NEXT SEVERAL DAYS MAY BRING UP LARGE AMOUNTS OF GULF MOISTURE THAT COULD RESULT IN LOCALLY HEAVY RAINFALL. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 23/2100Z 29.4N 93.0W 40 KT 12HR VT 24/0600Z 30.0N 94.1W 35 KT...INLAND 24HR VT 24/1800Z 30.4N 95.0W 30 KT...INLAND 36HR VT 25/0600Z 30.2N 95.7W 25 KT...INLAND 48HR VT 25/1800Z 29.6N 96.4W 20 KT...DISSIPATING INLAND 72HR VT 26/1800Z 28.8N 97.2W 20 KT...REMNANT LOW INLAND 96HR VT 27/1800Z...DISSIPATED INLAND |
