000 WTNT41 KNHC 072056 TCDAT1 TROPICAL STORM IDA DISCUSSION NUMBER 14 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112009 400 PM EST SAT NOV 07 2009 THE SATELLITE APPEARANCE OF IDA HAS NOT CHANGED SIGNIFICANTLY THIS AFTERNOON. THE AIRCRAFT FOUND THE CENTER A LITTLE NORTH OF THE EARLIER ESTIMATES...WELL EMBEDDED WITHIN THE CENTRAL DENSE OVERCAST. THE PLANE MEASURED A PEAK 850 MB FLIGHT-LEVEL WIND OF 68 KT AND A SFMR SURFACE WIND OF 60 KT. THESE DATA SUPPORT AN INITIAL INTENSITY OF 60 KT. CIRRUS ELEMENTS ARE MOVING NORTHEASTWARD... SUGGESTING MODERATE SOUTHWESTERLY UPPER-LEVEL FLOW OVER THE CYCLONE. HOWEVER IT DOES NOT APPEAR THAT SHEAR WILL BE STRONG ENOUGH IN THE SHORT-TERM TO INHIBIT SOME ADDITIONAL INTENSIFICATION. IDA WILL BE TRAVERSING THE VERY WARM WATER OF THE NORTHWESTERN CARIBBEAN SEA AND THE INTENSITY GUIDANCE NOW UNANIMOUSLY PREDICTS IDA TO BECOME A HURRICANE WITHIN 12 HOURS...AND THE OFFICIAL FORECAST FOLLOWS SUIT. AFTER IDA REACHES THE GULF OF MEXICO...THE SHEAR IS FORECAST TO INCREASE AND WATERS BEGIN TO COOL. THESE FACTORS SHOULD CONTRIBUTE TO MORE STEADY WEAKENING. IDA HAS BEEN MOVING NORTHWARD AT A SLIGHTLY FASTER FORWARD SPEED TODAY. THE TRACK GUIDANCE IS TIGHTLY CLUSTERED ON A NORTH- NORTHWESTWARD MOTION DURING THE NEXT 24 TO 36 HOURS. THE OFFICIAL FORECAST DURING THIS PERIOD REMAINS NEAR THE MODEL CONSENSUS BUT HAS BEEN ADJUSTED A LITTLE EASTWARD PRIMARILY DUE TO THE MORE NORTHWARD INITIAL POSITION AND HEADING. THEREAFTER...THERE REMAINS SIGNIFICANT DIFFERENCES IN THE GUIDANCE AS TO HOW IDA INTERACTS WITH A MID- TO UPPER-LEVEL TROUGH THAT MOVES INTO THE NORTHWESTERN GULF OF MEXICO IN A COUPLE OF DAYS. THE 12Z GFS...ECMWF...AND HWRF CONTINUE TO SHOW THE CYCLONE REACHING THE NORTHERN GULF COAST IN ABOUT 72 HOURS AS IT BECOMES AN EXTRATROPICAL CYCLONE. THE OFFICIAL FORECAST IS A LITTLE FASTER THAN THE PREVIOUS ONE...AND HAS ONCE AGAIN BEEN SHIFTED NORTHWARD. THE NEW TRACK NOW SHOWS A POSITION JUST SOUTH OF THE NORTHERN GULF COAST IN 3 DAYS. THEREAFTER...MOST OF THE GUIDANCE TURNS THE CYCLONE EASTWARD...AND SO DOES THE OFFICIAL FORECAST. BY 120 HOURS...SOME OF THE GUIDANCE SUGGEST THAT THE LOW WILL BE ABSORBED BY A FRONTAL BOUNDARY...AND THE OFFICIAL FORECAST DOES NOT PROVIDE A 5-DAY POSITION FOR THIS REASON. MOST OF THE GLOBAL MODELS SHOW A LARGE PRESSURE GRADIENT BETWEEN A HIGH PRESSURE RIDGE OVER THE SOUTHEASTERN UNITED STATES AND THE TROPICAL CYCLONE. THIS IS ALREADY CONTRIBUTING TO A LARGE AREA OF STRONG WINDS OVER THE SOUTHERN GULF OF MEXICO WHICH IS NOT DIRECTLY ATTRIBUTABLE TO IDA. FORECAST POSITIONS AND MAX WINDS INITIAL 07/2100Z 18.9N 84.3W 60 KT 12HR VT 08/0600Z 20.1N 84.8W 75 KT 24HR VT 08/1800Z 21.6N 85.8W 70 KT 36HR VT 09/0600Z 23.8N 87.2W 60 KT 48HR VT 09/1800Z 26.3N 88.0W 50 KT 72HR VT 10/1800Z 29.5N 87.3W 45 KT...EXTRATROPICAL 96HR VT 11/1800Z 29.5N 86.0W 40 KT...EXTRATROPICAL 120HR VT 12/1800Z...DISSIPATED $$ FORECASTER BROWN