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| #307056 (Received by flhurricane at: 3:43 AM 09.Nov.2009) TCDAT1 HURRICANE IDA DISCUSSION NUMBER 22 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112009 300 AM CST MON NOV 09 2009 DATA FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT SHOW THAT VERTICAL SHEAR IS BEGINNING TO TAKE A TOLL ON IDA. THE MINIMUM PRESSURE IS ESTIMATED TO HAVE RISEN TO 988 MB BASED ON A DROPSONDE MEASUREMENT OF 991 WITH ABOUT 30 KT OF WIND. ALSO...THE FLIGHT- LEVEL AND SFMR WIND DATA SUGGEST THAT THE LOW-LEVEL CENTER IS BECOMING INCREASINGLY DISPLACED TO THE SOUTH OF THE FLIGHT-LEVEL CENTER. THIS IS CONSISTENT WITH TRENDS SEEN IN RECENT GEOSTATIONARY AND MICROWAVE SATELLITE IMAGERY...AS THE COLDEST CLOUD TOPS HAVE BEEN DISPLACED TO THE NORTH OF THE AIRCRAFT FIXES. THE MAXIMUM 700-MB FLIGHT LEVEL WIND MEASURED BY THE AIRCRAFT SO FAR WAS 74 KT. BASED ON THESE DATA...THE INITIAL INTENSITY IS LOWERED TO 80 KT FOR THIS ADVISORY...AND THIS COULD BE A LITTLE GENEROUS. THE SHEAR OVER IDA IS CURRENTLY ANALYZED AT MORE THAN 30 KT BY UW-CIMSS...AND IS FORECAST TO INCREASE MARKEDLY OVER THE NEXT 24 HOURS. THIS...IN COMBINATION WITH COOLER WATERS ALONG THE TRACK OF IDA OVER THE NORTHERN GULF SHOULD RESULT IN A CONTINUED WEAKENING TREND. THE OFFICIAL INTENSITY FORECAST HAS BEEN ADJUSTED DOWNWARD ...AND IS CLOSE TO OR A LITTLE ABOVE THE ICON CONSENSUS THROUGH 36 HOURS. AT 48 HOURS...THE OFFICIAL FORECAST LEANS TOWARD THE DECAY SHIPS AND LGEM SINCE THE SYSTEM WILL BE WELL INLAND BY THAT TIME. AS IDA MOVES INTO COOLER WATERS AND A MORE BAROCLINIC ENVIRONMENT ...EXTRATROPICAL TRANSITION WILL LIKELY BEGIN IN THE NEXT 24 HOURS. MOST OF THE GUIDANCE SUGGESTS IDA WILL BE EXTRATROPICAL IN 48 HOURS AND THIS IS REFLECTED IN THE OFFICIAL FORECAST. THE LATEST FIXES FROM THE AIRCRAFT SUGGEST THAT IDA IS MOVING ALONG A HEADING OF 335/14...FASTER AND A LITTLE TO THE LEFT OF THE PREVIOUS TRACK. IDA IS EXPECTED TO ACCELERATE NORTHWARD TODAY AHEAD OF A MID- TO UPPER-LEVEL TROUGH MOVING EASTWARD ACROSS THE SOUTH-CENTRAL UNITED STATES AND NORTHERN GULF OF MEXICO. THE TRACK MODEL GUIDANCE CONTINUES TO BE IN GENERALLY GOOD AGREEMENT ON THIS SCENARIO...HOWEVER...THE UKMET AND ECMWF REMAIN WESTERN OUTLIERS WITH A TRACK CLOSER TO THE COAST OF SOUTHEASTERN LOUISIANA. THE OFFICIAL FORECAST HAS BEEN ADJUSTED WESTWARD FROM THE PREVIOUS PACKAGE THROUGH 24 HOURS TOWARD THE MULTI-MODEL CONSENSUS. AFTER LANDFALL...IDA IS EXPECTED TO SLOW AND TURN SHARPLY TOWARD THE EAST...AND THE NHC FORECAST CONTINUES TO FOLLOW THIS SCENARIO. MOST OF THE GLOBAL MODEL GUIDANCE...ALONG WITH THE GFDL...SHOW WHAT IS LEFT OF IDA DISSIPATING BY 72 HOURS AS IT IS ABSORBED INTO A FRONT THAT IS MOVING THROUGH THE SOUTHEASTERN U.S. BEHIND A DEVELOPING BAROCLINIC LOW OFF OF THE CAROLINAS. FORECAST POSITIONS AND MAX WINDS INITIAL 09/0900Z 25.1N 87.9W 80 KT 12HR VT 09/1800Z 27.2N 88.2W 75 KT 24HR VT 10/0600Z 29.6N 87.8W 70 KT 36HR VT 10/1800Z 30.9N 86.7W 45 KT...INLAND 48HR VT 11/0600Z 31.0N 85.0W 35 KT...EXTRATROPICAL INLAND 72HR VT 12/0600Z...ABSORBED BY FRONT $$ FORECASTER BRENNAN |
