Official Discussion issued by the National Hurricane Center
IKE (AL092008) DATA RELEASED: 9/11/2008 9:00:00 PM UTC
Copy of official data HURRICANE IKE DISCUSSION NUMBER 43 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092008 500 PM EDT THU SEP 11 2008 A PAIR OF DROPSONDES THIS AFTERNOON IN THE SOUTHEASTERN QUADRANT FINALLY PROVIDED SOME HARD DATA TO SUPPORT THE ADVISORY INTENSITY...WITH LOWER-LAYER MEAN WINDS OF 96 KT...WHICH ADJUST TO 80 KT AT THE SURFACE. AIRCRAFT DATA INDICATE THAT THE SMALL INNER WIND MAXIMUM HAS ALL BUT DISSIPATED...AND THE INNERMOST RADIUS OF MAXIMUM WINDS IS NOW AROUND 60 NMI. FLIGHT LEVEL WINDS WINDS THERE ARE ABOUT 100 KT...AND NEARLY THAT STRONG OUT TO AT LEAST 100 NMI. AS THE INNER WIND MAXIMUM DISSIPATED...THE MINIMUM PRESSURE ROSE TO ABOUT 954 MB...BUT HAS SINCE FALLEN TO 950 MB. THE INTENSITY GUIDANCE HAS COME DOWN SINCE THIS MORNING...ALTHOUGH THE GFDL STILL MAKES IKE A MAJOR HURRICANE. FACTORS INHIBITING DEVELOPMENT INCLUDE THE LARGE BROAD WIND FIELD...STRONG WINDS OVER AREAS OF LIMITED OCEAN HEAT CONTENT ALONG AND NORTH OF THE PATH OF IKE...AND AN UPPER-LEVEL RIDGE OVER TEXAS THAT IS FORCING DESCENT AND CREATING DRY AIR AHEAD OF THE PATH OF THE HURRICANE. INDEED... CONVECTION ON THE WEST SIDE OF IKE HAS BEEN RATHER THIN FOR MUCH OF THE DAY. HOWEVER...THIS LATTER UPPER FEATURE IS FORECAST TO SLIDE NORTHEASTWARD AS IKE ENTERS THE NORTHWESTERN GULF...AND IN THIS CONFIGURATION WOULD PROVIDE AN UPPER PATTERN MORE CONDUCIVE TO STRENGTHENING RIGHT BEFORE LANDFALL. CURRENTLY THE OUTFLOW IS VERY WELL ESTABLISHED TO THE NORTHEAST AND SOUTHWEST OF THE CENTER. THE OFFICIAL FORECAST IS UNCHANGED FROM THE PREVIOUS ADVISORY AND IS IN BEST AGREEMENT WITH THE GFDL GUIDANCE. IKE IS MOVING WEST-NORTHWESTWARD AROUND THE PERIPHERY OF A RIDGE OF HIGH PRESSURE EXTENDING FROM THE WESTERN ATLANTIC WESTWARD OVER THE SOUTHEASTERN UNITED STATES. A DEEP LAYER TROUGH CURRENTLY EXTENDS INTO THE SOUTHWESTERN STATES...AND IKE IS EXPECTED TO GENTLY RECURVE BETWEEN THESE TWO FEATURES IN 48-72 HOURS. THE OBJECTIVE GUIDANCE HAS SHIFTED SLIGHTLY TO THE RIGHT...AND IS RATHER TIGHTLY CLUSTERED THROUGH LANDFALL. AS THE UPPER HIGH OVER TEXAS MOVES NORTHEASTWARD...A SLIGHT BEND OF THE TRACK TO THE LEFT IS EXPECTED PRIOR TO THE BEGINNING OF RECURVATURE. THE OFFICIAL FORECAST HAS BEEN NUDGED SLIGHTLY TO THE RIGHT...BUT IS STILL JUST LEFT OF THE MODEL CONSENSUS. IT IS WORTH NOTING THAT THE AVERAGE 36-HOUR OFFICIAL FORECAST ERROR IS ABOUT 80 NMI. BECAUSE OF THE VERY LARGE EXPANSE OF HURRICANE FORCE WINDS...IKE WILL CREATE A STORM SURGE WELL IN EXCESS OF WHAT WOULD NORMALLY BE ASSOCIATED WITH A STORM OF ITS INTENSITY. FORECAST POSITIONS AND MAX WINDS INITIAL 11/2100Z 26.0N 89.4W 85 KT 12HR VT 12/0600Z 26.6N 90.9W 90 KT 24HR VT 12/1800Z 27.6N 93.0W 95 KT 36HR VT 13/0600Z 29.0N 95.0W 105 KT 48HR VT 13/1800Z 31.5N 95.5W 65 KT...INLAND 72HR VT 14/1800Z 37.0N 90.5W 30 KT...INLAND 96HR VT 15/1800Z...ABSORBED IN FRONTAL ZONE $$ FORECASTER FRANKLIN |