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| #306312 (Received by flhurricane at: 9:43 PM 05.Nov.2009) TCDAT1 TROPICAL DEPRESSION IDA DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112009 1000 PM EST THU NOV 05 2009 SURFACE OBSERVATIONS AND CONVENTIONAL SATELLITE IMAGERY INDICATE THAT IDA HAS WEAKENED TO A TROPICAL DEPRESSION. WHAT REMAINS OF THE DIMINISHING DEEP CONVECTION IS CURRENTLY CONFINED TO NORTHWEST AND NORTHEAST QUADRANTS. SOME FURTHER WEAKENING IS LIKELY DURING THE NEXT 12 TO 24 HOURS AS IDA CONTINUES ON A GENERAL NORTHWARD TRACK OVER NORTHEASTERN NICARAGUA AND EASTERN HONDURAS. AROUND THE 36 HOUR PERIOD...THE CYCLONE SHOULD EMERGE OVER THE NORTHWEST CARIBBEAN SEA AND...ASSUMING THE CIRCULATION IS NOT TOO SEVERELY DISRUPTED BY ITS PASSAGE OVER LAND...THE SYSTEM SHOULD RESTRENGTHEN INTO A TROPICAL STORM. HOWEVER...THE GLOBAL MODELS INDICATE ONLY A MARGINALLY FAVORABLE UPPER-LEVEL WIND ENVIRONMENT OVER THE REGION...WHICH SHOULD CURTAIL SIGNIFICANT INTENSIFICATION AS IDA HEADS IN THE GENERAL DIRECTION OF THE YUCATAN CHANNEL. AFTER IDA ENTERS THE SOUTHERN GULF OF MEXICO....THE INTENSITY FORECAST IS HIGHLY UNCERTAIN. THE LARGE-SCALE MODELS ALL AGREE ON AN INCREASINGLY STRONG VERTICAL SHEAR ENVIRONMENT DEVELOPING OVER THE GULF OF MEXICO TOWARD THE END OF THE FORECAST PERIOD. THE GFDL AND HWRF MODELS...PARTICULARLY THE FORMER...SHOW SIGNIFICANT INTENSIFICATION OF IDA IN THE LATTER PART OF THE PERIOD. IT SHOULD BE RECALLED HOWEVER THAT THESE MODELS HAVE BEEN KNOWN TO HAVE A HIGH BIAS IN STRONGLY SHEARED ENVIRONMENTS...AS WAS THE CASE WITH TROPICAL STORMS DANNY...ERIKA...AND HENRI OF THIS YEAR. CONSEQUENTLY...THE OFFICIAL WIND SPEED FORECAST LEANS MORE TOWARD THE WEAKER LGEM AND SHIPS PREDICTIONS. THE INITIAL MOTION IS ESTIMATED TO BE 330/4...WITHIN THE SOUTHERLY STEERING FLOW ON THE WEST SIDE OF A WEAK MID-LEVEL RIDGE. WITH THE EXCEPTION OF FORWARD SPEED DISPARITIES...THE GLOBAL AND REGIONAL MODELS CONTINUE TO INDICATE A GENERAL NORTH TO NORTH-NORTHWESTWARD MOTION INTO THE CENTRAL GULF OF MEXICO OVER THE NEXT 4 DAYS. AROUND THE END OF THE PERIOD...MOST OF THE TRACK GUIDANCE SHOWS A TURN TO THE RIGHT AS IDA BEGINS TO INTERACT WITH THE WESTERLIES. THE OFFICIAL FORECAST HAS CHANGED LITTLE FROM THE PREVIOUS ONE AND IS CLOSE TO THE MODEL CONSENSUS. THE BIGGEST IMPACT OF THIS SLOW-MOVING SYSTEM DURING THE NEXT DAY OR SO WILL LIKELY BE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES CAUSED BY EXTREMELY HEAVY RAIN OVER PORTIONS OF NICARAGUA AND HONDURAS. FORECAST POSITIONS AND MAX WINDS INITIAL 06/0300Z 13.8N 84.1W 30 KT 12HR VT 06/1200Z 14.4N 84.1W 25 KT...INLAND 24HR VT 07/0000Z 15.4N 84.2W 25 KT...INLAND 36HR VT 07/1200Z 16.6N 84.5W 35 KT...OVER WATER 48HR VT 08/0000Z 17.7N 85.0W 40 KT 72HR VT 09/0000Z 20.3N 86.2W 45 KT 96HR VT 10/0000Z 23.0N 87.5W 45 KT 120HR VT 11/0000Z 26.0N 87.0W 45 KT $$ FORECASTER PASCH/ROBERTS |
