ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM IDA DISCUSSION NUMBER 15 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112009 1000 PM EST SAT NOV 07 2009 THERE HAS BEEN LITTLE CHANGE TO THE SATELLITE APPEARANCE OF IDA SINCE THE AIR FORCE PLANE LEFT EARLIER THIS AFTERNOON. THE LOW-LEVEL CENTER IS STILL EMBEDDED WITHIN A LARGE CENTRAL DENSE OVERCAST ALTHOUGH RECENT MICROWAVE DATA SUGGEST THAT THE SYSTEM IS BEING IMPACTED BY SOME SOUTHERLY SHEAR. THE INTENSITY WILL BE HELD AT 60 KT FOR THIS ADVISORY...WHICH IS SUPPORTED BY DVORAK ESTIMATES OF 55 KT FROM BOTH TAFB AND SAB AND AN OBJECTIVE ADT ESTIMATE OF 61 KT. ANOTHER AIR FORCE RECONNAISSANCE AIRCRAFT IS SCHEDULED TO INVESTIGATE IDA IN A FEW HOURS TO PROVIDE UPDATED INFORMATION. IDA HAS TURNED TO THE NORTH-NORTHWEST WITH AN INITIAL MOTION OF 340 DEGREES AT 10 KT AS IT IS STEERED BETWEEN AN AMPLIFIED TROUGH OVER MEXICO AND A MID-LEVEL RIDGE THAT EXTENDS FROM THE SOUTHEASTERN U.S. TO HISPANIOLA. THE TRACK GUIDANCE IS IN EXCELLENT AGREEMENT THROUGH 48 HOURS ON A CONTINUED NORTH-NORTHWESTWARD MOTION...AND THE NEW OFFICIAL FORECAST IS ONLY SLIGHTLY TO THE EAST OF THE PREVIOUS FORECAST. THEREAFTER...ALL THE MODELS BRING IDA TO THE COAST NEAR THE FLORIDA PANHANDLE AS AN EXTRATROPICAL CYCLONE BUT QUICKLY TURN IT TO THE SOUTHEAST AS THE ABSORBING COLD FRONT PUSHES SOUTHWARD OVER THE GULF. ALTHOUGH SOME SHEAR IS AFFECTING IDA...IT IS NOT PROHIBITIVELY STRONG. STRONG UPPER-LEVEL WINDS NORTH OF THE SYSTEM ARE PROVIDING SOME DIFFLUENCE ALOFT...AND THIS WILL CONTINUE TO GIVE IDA A 24-36 HOUR WINDOW TO STRENGTHEN TO A HURRICANE. THE SHEAR IS EXPECTED TO INCREASE AFTER 36 HOURS AND SHOULD LEAD TO SOME WEAKENING...BUT THE NEW INTENSITY GUIDANCE INDICATES THAT THIS WEAKENING COULD BE SLOWER TO OCCUR THAN PREVIOUSLY FORECAST. IDA SHOULD BEGIN THE EXTRATROPICAL TRANSITION PROCESS AROUND 48 HOURS AND BE FULLY EXTRATROPICAL BY 72 HOURS. A TIGHT PRESSURE GRADIENT BETWEEN IDA AND HIGH PRESSURE LOCATED OVER THE SOUTHEASTERN UNITED STATES IS ALREADY PRODUCING STRONG WINDS OVER THE SOUTHEASTERN GULF OF MEXICO...BUT THESE WINDS ARE NOT DIRECTLY ATTRIBUTABLE TO THE CIRCULATION OF IDA. FORECAST POSITIONS AND MAX WINDS INITIAL 08/0300Z 20.1N 84.6W 60 KT 12HR VT 08/1200Z 21.2N 85.3W 70 KT 24HR VT 09/0000Z 23.0N 86.5W 70 KT 36HR VT 09/1200Z 25.4N 87.6W 65 KT 48HR VT 10/0000Z 27.7N 87.9W 60 KT 72HR VT 11/0000Z 30.0N 86.5W 45 KT...EXTRATROPICAL 96HR VT 12/0000Z 29.0N 85.5W 35 KT...EXTRATROPICAL 120HR VT 13/0000Z...ABSORBED BY FRONT $$ FORECASTER BERG/FRANKLIN NNNN
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Page last modified: Thursday, 31-Dec-2009 12:09:12 UTC