000 WTNT44 KNHC 040838 TCDAT4 HURRICANE IKE DISCUSSION NUMBER 13 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092008 500 AM EDT THU SEP 04 2008 SATELLITE IMAGES INDICATE THAT IKE HAS INTENSIFIED FURTHER...WITH THE EYE EMBEDDED IN EVEN COLDER CLOUD TOPS THAN BEFORE. THE LATEST DVORAK DATA T-NUMBERS ARE UP TO 6.5 WHICH SUPPORTS AN INTENSITY OF 125 KT...AND THIS IS USED FOR THE CURRENT ADVISORY. IN SUCH INTENSE HURRICANES...FLUCTUATIONS IN STRENGTH DUE TO INNER-CORE EVOLUTIONS SUCH AS EYEWALL REPLACEMENTS ARE NEARLY IMPOSSIBLE TO PREDICT. HOWEVER...THE SHIPS MODEL SHOWS OVER 30 KT OF VERTICAL SHEAR ON IKE WITHIN THE NEXT 24-36 HOURS DUE TO A STRENGTHENING UPPER-LEVEL HIGH TO THE NORTHWEST OF THE HURRICANE. THIS LARGE-SCALE ENVIRONMENTAL INFLUENCE SHOULD INDUCE SOME WEAKENING... AND THAT IS WHAT IS INDICATED IN THE OFFICIAL WIND SPEED FORECAST. LATER ON IN THE FORECAST PERIOD...SOME RE-STRENGTHENING IS PROBABLE AS THE SHEAR WEAKENS AND THE THERMODYNAMIC ENVIRONMENT IS EXPECTED TO BE FAVORABLE. THE OFFICIAL FORECAST MIGHT BE CONSERVATIVE BUT IT REFLECTS OUR LACK OF SKILL IN FORECASTING TROPICAL CYCLONE INTENSITY IN 3-5 DAYS. IKE CONTINUES TO MOVE WEST-NORTHWESTWARD OR AROUND 290/15. THERE HAS BEEN LITTLE CHANGE TO THE TRACK FORECAST OR FORECAST REASONING. A DEEP-LAYER HIGH IS DEPICTED BY THE GLOBAL MODELS TO BUILD TO THE NORTHWEST OF THE HURRICANE WITHIN THE NEXT COUPLE OF DAYS. THIS WOULD LIKELY CAUSE THE HEADING OF IKE TO BEND WESTWARD TO WEST-SOUTHWESTWARD. LATE IN THE FORECAST PERIOD IT IS EXPECTED THAT IKE WILL HAVE PASSED THE CENTER OF THE HIGH...AND TURN BACK TOWARD THE WEST AND WEST-NORTHWEST. THE BIG QUESTIONS IS HOW THE HURRICANE RESPONDS TO THE WEAKNESS IN THE MID-TROPOSPHERIC RIDGE OVER THE SOUTHEASTERN U.S. AROUND DAY 5. LOOKING AT THE VARIOUS TRACK MODELS IN THIS TIME FRAME...WE SEE THAT THE ECMWF IS THE WESTERNMOST AND THE GFS IS THE NORTHEASTERNMOST. THE OFFICIAL TRACK FORECAST LIES BETWEEN THESE EXTREMES AND LEANS TOWARD THE ECMWF. THIS IS A LITTLE TO THE LEFT OF THE DYNAMICAL MODEL CONSENSUS AND QUITE SIMILAR TO THE PREVIOUS NHC FORECAST. BECAUSE OF THE UNCERTAINTIES IN 4- AND 5-DAY TRACK FORECASTS...IT IS STILL TOO EARLY TO SAY WHAT LAND AREAS ARE LIKELY TO BE IMPACTED BY THIS HURRICANE. FORECAST POSITIONS AND MAX WINDS INITIAL 04/0900Z 22.7N 55.8W 125 KT 12HR VT 04/1800Z 23.5N 57.7W 125 KT 24HR VT 05/0600Z 24.0N 60.2W 115 KT 36HR VT 05/1800Z 24.0N 62.6W 110 KT 48HR VT 06/0600Z 23.4N 64.9W 110 KT 72HR VT 07/0600Z 22.5N 69.5W 115 KT 96HR VT 08/0600Z 23.0N 73.5W 115 KT 120HR VT 09/0600Z 25.0N 76.5W 115 KT $$ FORECASTER PASCH