Sat Nov 7 17:10:05 EST 2009 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  TCDAT1 TROPICAL STORM IDA DISCUSSION NUMBER 13 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112009 1000 AM EST SAT NOV 07 2009 RECENT MICROWAVE IMAGERY SUGGESTS THAT THE STRUCTURE OF IDA HAS CONTINUED TO IMPROVE THIS MORNING...WITH A COUPLE OF HOOKING BANDS NEAR THE CENTER. VISIBLE IMAGERY SHOWS AN EXPANDING CENTRAL DENSE OVERCAST FEATURE AND NO OBVIOUS SIGNS OF SIGNIFICANT SHEAR. THE LATEST DVORAK INTENSITY ESTIMATES ARE 45 KT FROM BOTH AGENCIES...BUT GIVEN THE INCREASE IN ORGANIZATION SINCE THAT TIME THE INITIAL INTENSITY HAS BEEN RAISED TO 50 KT. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS CURRENTLY EN ROUTE TO INVESTIGATE THE STORM. IDA IS MOVING NORTHWARD OR 355/8. IDA IS EXPECTED TO MOVE NORTH-NORTHWESTWARD BETWEEN A MID-LEVEL ANTICYCLONE OVER THE NORTH-CENTRAL CARIBBEAN SEA AND A DEEP-LAYER TROUGH OVER SOUTHERN MEXICO. THE TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH 36 TO 48 HOURS AND THE NHC FORECAST REMAINS IN LINE WITH THE MODEL CONSENSUS DURING THAT TIME. THEREAFTER...THERE IS A LARGE SPREAD AMONG THE MODELS AS TO HOW IDA INTERACTS WITH A MID- TO UPPER-LEVEL TROUGH DIGGING INTO THE NORTHERN GULF OF MEXICO. THE GFS...ECMWF...AND HWRF ALL MOVE THE CYCLONE QUICKLY NORTHWARD AND SHOW IT REACHING THE NORTHERN GULF COAST IN ABOUT 3 DAYS AS IT BECOMES AN EXTRATROPICAL CYCLONE. THE REMAINDER OF THE GUIDANCE HAS TRENDED NORTHWARD...BUT TURNS THE SYSTEM GENERALLY EASTWARD BEFORE REACHING THE NORTHERN GULF COAST. FOR NOW...THE OFFICIAL FORECAST IS BETWEEN THESE TWO SCENARIOS...BUT HAS BEEN ADJUSTED NORTHWARD TO ACCOUNT FOR THE LATEST TRENDS. ENVIRONMENTAL CONDITIONS...WHILE NOT IDEAL...APPEAR CONDUCIVE ENOUGH FOR STRENGTHENING DURING THE NEXT DAY OR SO AS THE CYCLONE TRAVERSES THE NORTHWEST CARIBBEAN SEA. THE OFFICIAL FORECAST HAS BEEN ADJUSTED UPWARD FROM THE PREVIOUS ONE BASED ON RECENT TRENDS. ONCE IDA REACHES THE GULF OF MEXICO...SHEAR IS FORECAST TO INCREASE AND WATERS BEGIN TO COOL. THESE FACTORS SHOULD CONTRIBUTE TO WEAKENING...HOWEVER THE INTERACTION WITH THE UPPER-TROUGH AND AN EXPECTED EXTRATROPICAL TRANSITION WILL LIKELY RESULT IN LESS WEAKENING THAN TYPICAL...GIVEN THE STRONG SHEAR. 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 07/1500Z 17.9N 84.1W 50 KT 12HR VT 08/0000Z 18.9N 84.6W 55 KT 24HR VT 08/1200Z 20.3N 85.5W 60 KT 36HR VT 09/0000Z 22.2N 86.8W 55 KT 48HR VT 09/1200Z 24.6N 88.0W 45 KT 72HR VT 10/1200Z 28.5N 88.0W 45 KT...EXTRATROPICAL 96HR VT 11/1200Z 29.0N 86.5W 40 KT...EXTRATROPICAL 120HR VT 12/1200Z 28.0N 85.0W 35 KT...EXTRATROPICAL $$ FORECASTER BROWN/CANGIALOSI/BLAKE  TCDAT1 TROPICAL STORM IDA DISCUSSION NUMBER 12 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112009 400 AM EST SAT NOV 07 2009 THE SATELLITE PRESENTATION OF IDA HAS IMPROVED OVER THE PAST SEVERAL HOURS...WITH AN INCREASE IN DEEP CONVECTION NEAR THE ESTIMATED LOCATION OF THE LOW LEVEL CENTER. THE INITIAL INTENSITY IS RAISED TO 40 KT BASED ON A BLEND OF DVORAK ESTIMATES OF 35 KT FROM SAB AND 45 KT FROM TAFB. THE INITIAL MOTION ESTIMATE IS 350/07...A LITTLE FASTER THAN BEFORE. IDA IS MOVING NORTHWARD BETWEEN A MID-LEVEL ANTICYCLONE OVER THE NORTH-CENTRAL CARIBBEAN SEA AND A DEEP-LAYER TROUGH OVER SOUTHERN MEXICO. MOST OF THE TRACK GUIDANCE IS TIGHTLY CLUSTERED THROUGH 48 HOURS...AND THE OFFICIAL FORECAST THROUGH THAT TIME IS CLOSE TO THE MODEL CONSENSUS BUT A LITTLE FASTER THAN THE PREVIOUS PACKAGE. BEYOND 48 HOURS...THE GLOBAL MODELS SHOW A MID- TO UPPER-LEVEL SHORTWAVE TROUGH DIGGING INTO THE NORTHERN GULF OF MEXICO. WHILE THE DETAILS ON THE TIMING AND DEGREE OF THE INTERACTION BETWEEN IDA AND THE TROUGH DIFFER...MOST OF THE MODELS...WITH THE EXCEPTION OF THE NOGAPS AND GFDN...SHOW IDA TURNING NORTHWARD AND THEN NORTHEASTWARD IN 3 OR 4 DAYS. IDA IS EXPECTED TO BECOME EXTRATROPICAL DURING THIS TIME AS IT BECOMES INVOLVED WITH A LOW-LEVEL FRONTAL ZONE ALONG THE NORTHERN GULF COAST. BY DAY 5 MOST OF THE GUIDANCE SHOWS THE FRONT...AND WHAT IS LEFT OF IDA... TURNING SOUTHWARD OR SOUTHEASTWARD IN RESPONSE TO A LARGE SCALE MID- TO UPPER-LEVEL TROUGH AMPLIFYING OVER EASTERN NORTH AMERICA. AT DAYS 3 THROUGH 5 THE NEW OFFICIAL THE FORECAST IS ADJUSTED A LITTLE NORTHWARD TOWARD THE MODEL CONSENSUS. WHILE IDA WILL BE MOVING OVER VERY WARM WATERS FOR THE NEXT COUPLE OF DAYS THE ENVIRONMENT WILL NOT BE IDEAL FOR STRENGTHENING...AS THE SHIPS MODEL SHOWS ABOUT 20 KT OF VERTICAL SHEAR OVER THE CYCLONE. BEYOND THAT TIME...THE SHEAR IS FORECAST TO INCREASE FURTHER AS IDA BEGINS TO INTERACT WITH THE MID- TO UPPER-LEVEL SHORTWAVE. THE OFFICIAL FORECAST IS ADJUSTED UPWARD A LITTLE GIVEN THE OBSERVED INTENSITY TRENDS...AND SHOWS A PEAK OF 50 KT IN 36 HOURS. THIS IS IN BEST AGREEMENT WITH THE SHIPS MODEL AND CLOSE TO THE ICON INTENSITY CONSENSUS. GRADUAL WEAKENING IS EXPECTED TO BEGIN ON DAY 2 AS IDA ENCOUNTERS THE STRONGER SHEAR AND BEGINS TO UNDERGO EXTRATROPICAL TRANSITION. MOST OF THE GLOBAL MODELS SHOW A LARGE PRESSURE GRADIENT DEVELOPING BETWEEN A HIGH PRESSURE RIDGE OVER THE SOUTHEASTERN UNITED STATES AND THE TROPICAL CYCLONE. THIS WILL CONTRIBUTE TO A LARGE AREA OF STRONG WINDS OVER THE GULF OF MEXICO NOT DIRECTLY ATTRIBUTABLE TO IDA. THE ISSUANCE OF A TROPICAL STORM WATCH IS REQUIRED AT THIS TIME FOR PORTIONS OF THE YUCATAN PENINSULA AND WESTERN CUBA. FORECAST POSITIONS AND MAX WINDS INITIAL 07/0900Z 17.1N 84.1W 40 KT 12HR VT 07/1800Z 18.1N 84.4W 45 KT 24HR VT 08/0600Z 19.5N 85.0W 45 KT 36HR VT 08/1800Z 21.0N 86.0W 50 KT 48HR VT 09/0600Z 23.0N 87.1W 45 KT 72HR VT 10/0600Z 26.5N 88.0W 45 KT 96HR VT 11/0600Z 28.0N 86.5W 40 KT...EXTRATROPICAL 120HR VT 12/0600Z 27.0N 85.0W 35 KT...EXTRATROPICAL $$ FORECASTER BRENNAN  424 WTNT41 KNHC 070857 TCDAT1 TROPICAL DEPRESSION IDA DISCUSSION NUMBER 11 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112009 1000 PM EST FRI NOV 06 2009 A 2302 UTC SSMIS MICROWAVE PASS INDICATED THAT THE LOW-LEVEL CENTER OF IDA WAS LOCATED JUST OFF THE NORTHEASTERN COAST OF HONDURAS AND WAS DISPLACED TO THE SOUTH AND SOUTHEAST OF THE DEEP CONVECTION. NEW CONVECTION IS DEVELOPING CLOSE TO THE CENTER...AND DVORAK ESTIMATES FROM TAFB AND SAB ARE 25 KT AND 30 KT...RESPECTIVELY. NOAA BUOY 42057...LOCATED ABOUT 150 N MI EAST-NORTHEAST OF THE CENTER...RECENTLY REPORTED A 1-MINUTE SUSTAINED WIND OF 35 KT...BUT IT APPEARS THAT THIS OCCURRED WITH THE PASSAGE OF A SQUALL AND MAY NOT BE REPRESENTATIVE OF THE OVERALL CIRCULATION. THEREFORE...IDA IS KEPT AS A TROPICAL DEPRESSION FOR THIS ADVISORY...BUT IT IS PROBABLY VERY CLOSE TO REGAINING TROPICAL STORM STATUS. IDA CONTINUES TO MOVE NORTHWARD AT 360/6. A MID-LEVEL ANTICYCLONE BETWEEN JAMAICA AND HISPANIOLA AND A DEEP-LAYER TROUGH OVER MEXICO ARE EXPECTED TO STEER IDA NORTH-NORTHWESTWARD THROUGH THE NEXT 72 HOURS. THE TRACK GUIDANCE IS IN GOOD AGREEMENT DURING THIS PERIOD ALTHOUGH THE GFDL AND HWRF MODELS ARE THE EASTERNMOST MODELS AND HAVE FORCED THE MODEL CONSENSUS A LITTLE MORE TO THE EAST. THE FORECAST BEYOND 72 HOURS IS STILL COMPLEX AND IS DEPENDENT ON HOW IDA INTERACTS WITH THE FRONT AND SHORTWAVE TROUGH OVER THE GULF OF MEXICO. MOST OF THE GUIDANCE SHOWS IDA BECOMING EXTRATROPICAL BY 96 HOURS ONCE IT MERGES WITH THE FRONT...BUT THE SOLUTIONS VARY ON WHERE THE LOW GOES NEXT. ONLY THE 1200 UTC ECMWF AND UKMET SHOW IDA BECOMING PICKED UP BY A SHORTWAVE TROUGH AND MOVING NORTHEASTWARD OVER THE NORTHERN GULF. THE OTHER MODELS INDICATE A MORE PRONOUNCED SOUTHWARD MOTION AFTER 96 HOURS...AND THE OFFICIAL FORECAST NOW SHOWS A SLOW SOUTHEASTWARD TURN AT 120 HOURS. ALTHOUGH WATERS ARE WARM OVER THE NORTHWESTERN CARIBBEAN...VERTICAL SHEAR IS EXPECTED TO HAMPER MUCH INTENSIFICATION OVER THE NEXT FEW DAYS. THE GFDL AND HWRF MAKE IDA A HURRICANE OVER THE CENTRAL GULF OF MEXICO...A SCENARIO THAT DOES NOT SEEM PLAUSIBLE IN THE FACE OF WESTERLY SHEAR THAT IS EXPECTED TO INCREASE TO 50 OR 60 KT BY DAY 4. THE OFFICIAL FORECAST INDICATES SOME SLOW STRENGTHENING OVER THE NEXT SEVERAL DAYS BUT PEAKS THE INTENSITY AT 45 KT...WHICH IS JUST BELOW THE INTENSITY CONSENSUS. IT IS OF NOTE THAT MOST OF THE GLOBAL MODELS ARE SHOWING A LARGE PRESSURE GRADIENT BETWEEN A HIGH OVER THE SOUTHEASTERN UNITED STATES AND THE TROPICAL CYCLONE. THIS COULD CONTRIBUTE TO A LARGE AREA OF STRONG WINDS OVER THE GULF OF MEXICO NOT DIRECTLY ATTRIBUTABLE TO IDA. FORECAST POSITIONS AND MAX WINDS INITIAL 07/0300Z 16.2N 84.0W 30 KT 12HR VT 07/1200Z 17.1N 84.2W 35 KT 24HR VT 08/0000Z 18.4N 84.8W 35 KT 36HR VT 08/1200Z 19.7N 85.5W 40 KT 48HR VT 09/0000Z 21.4N 86.5W 45 KT 72HR VT 10/0000Z 25.5N 88.0W 45 KT 96HR VT 11/0000Z 27.5N 87.0W 45 KT...EXTRATROPICAL 120HR VT 12/0000Z 26.5N 85.6W 35 KT...EXTRATROPICAL $$ FORECASTER BERG