ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM IDA DISCUSSION NUMBER 26 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112009 300 AM CST TUE NOV 10 2009 THE CENTER OF IDA IS NOW DEVOID OF DEEP CONVECTION...AS THE COLDEST CLOUD TOPS HAVE CONTINUED TO SHEAR OFF TOWARD THE NORTH AND EAST OVER THE PAST SEVERAL HOURS. DATA FROM AIRCRAFT RECONNAISSANCE SHOW THAT THE CENTRAL PRESSURE HAS SLOWLY RISEN TO 999 MB. THE HIGHEST 850-MB FLIGHT LEVEL WIND REPORTED BY THE HURRICANE HUNTER AIRCRAFT WAS 53 KT AT 0733 UTC...AND THE HIGHEST RELIABLE SFMR WINDS WERE AROUND 40 KT. WINDS AT THE NUMEROUS MARINE PLATFORMS ALONG THE GULF COAST HAVE ALSO BEEN SLOWLY DECREASING OVER THE PAST FEW HOURS. BASED ON ALL THIS...THE INITIAL INTENSITY IS LOWERED TO 45 KT FOR THIS ADVISORY. A GRADUAL SPIN DOWN OF THE SYSTEM IS FORECAST... ALTHOUGH IDA IS STILL EXPECTED TO BE AT TROPICAL STORM INTENSITY WHEN IT COMPLETES EXTRATROPICAL TRANSITION LATER TODAY. MOST OF THE GUIDANCE SHOWS THE LOW-LEVEL CIRCULATION OF IDA BEING ABSORBED INTO A FRONTAL ZONE ASSOCIATED WITH A BAROCLINIC LOW THAT DEVELOPS OFF THE SOUTHEAST U.S. COAST IN ABOUT 48 HOURS. AIRCRAFT FIXES AND SATELLITE IMAGERY OVERNIGHT INDICATED THAT IDA WAS MOVING ONLY VERY SLOWLY NORTHWARD FOR SEVERAL HOURS. HOWEVER THE LAST COUPLE OF AIRCRAFT FIXES AND MULTI-CHANNEL SATELLITE IMAGERY SUGGEST THAT A FASTER MOTION JUST EAST OF DUE NORTH MAY HAVE BEGUN...AND THE INITIAL MOTION ESTIMATE IS 005/08. DATA FROM THE AIRCRAFT AND SATELLITE IMAGERY ALSO SUGGEST THAT THE LOW-LEVEL CENTER IS BECOMING ELONGATED AND LESS WELL-DEFINED. THE DYNAMICAL GUIDANCE IS INSISTENT ON A TURN TOWARD THE NORTHEAST WHICH COULD BE BEGINNING NOW AND FINALLY WOULD BRING THE CENTER INLAND LATER TODAY. THE OFFICIAL FORECAST IS SLOWER AND FARTHER SOUTH THAN THE PREVIOUS PACKAGE DUE TO THE SLOWER INITIAL MOTION AND MORE WESTERLY INITIAL POSITION AND A SOUTHWARD TREND IN THE MODEL GUIDANCE. THE FACT THAT THE LANDFALL OF IDA HAS BEEN DELAYED HAS LITTLE SIGNIFICANCE SINCE THE TROPICAL STORM FORCE WINDS COVER A LARGE AREA AWAY FROM THE CENTER AND MOST OF THE HEAVY RAINFALL HAS ALREADY SPREAD ONSHORE. FORECAST POSITIONS AND MAX WINDS INITIAL 10/0900Z 29.9N 88.5W 45 KT 12HR VT 10/1800Z 30.8N 88.0W 35 KT...EXTRATROPICAL 24HR VT 11/0600Z 31.0N 86.4W 30 KT...EXTRATROPICAL 36HR VT 11/1800Z 30.4N 84.4W 25 KT...EXTRATROPICAL 48HR VT 12/0600Z...DISSIPATED $$ FORECASTER BRENNAN NNNN
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Page last modified: Thursday, 31-Dec-2009 12:09:12 UTC