ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER 7 NATIONAL WEATHER SERVICE MIAMI FL 5 AM EDT THU SEP 13 2001 AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT DEVELOPED MECHANICAL PROBLEMS ENROUTE TO TROPICAL DEPRESSION EIGHT AND HAD TO TURN BACK... SO NO IN-SITU DATA WAS AVAILABLE FOR THIS ADVISORY. HOWEVER...DOPPLER RADAR DATA FROM KEY WEST ALONG WITH INFRARED SATELLITE DATA INDICATE THAT THE DEPRESSION HAS CONTINUED TO BECOME BETTER ORGANIZED. DEEP CONVECTION HAS FINALLY DEVELOPED AND PERSISTED NEAR THE LOW-LEVEL CENTER...WHICH REMAINS SITUATED JUST SOUTH OR SOUTHEAST OF EAST GULF BUOY 42003. AT 13/06Z SHIP WPKD...LOCATED ABOUT 70 NM SOUTHEAST OF THE CENTER...REPORTED A 32 KT SUSTAINED WIND AND A PRESSURE OF 1006 MB...WHICH SUGGESTS THAT THIS SYSTEM IS NEAR TROPICAL STORM STRENGTH. UPPER-LEVEL OUTFLOW IS GOOD IN THE SOUTHEAST SEMICIRCLE...BUT IS RESTRICTED TO THE NORTHWEST DUE TO MODERATE UPPER-LEVEL SHEAR. THE INITIAL MOTION ESTIMATE IS QUASI-STATIONARY. THERE REMAINS CONSIDERABLE DIVERGENCE AMONG THE VARIOUS NHC FORECAST MODELS... ESPECIALLY AMONG THE GLOBAL MODELS. NOGAPS AND THE UKMET MODELS CONTINUE TO TAKE THE DEPRESSION SLOWLY WEST OR WEST-SOUTHWESTWARD... WHILE THE AVN...GFDL...AND GFDN MODELS KEEP THE CYCLONE QUASI-STATIONARY FOR ABOUT 24 HOURS AND THEN SLOWLY MOVE IT NORTHEASTWARD TOWARD THE WEST COAST OF THE FLORIDA PENINSULA AS A RATHER FORMIDABLE TROPICAL CYCLONE. BY 72 HOURS...THE UKMET MODEL BEGINS TO TAKE THE CYCLONE TOWARD THE NORTHEAST...WHILE THE AVN MODEL TAKES THE DEPRESSION INLAND NEAR THE CEDAR KEY FLORIDA AREA IN ABOUT 72 HOURS. THE GFDN AND GFDL MODELS TAKE THE CYCLONE INLAND ALONG THE FLORIDA WEST COAST OVER OR JUST NORTH OF TAMPA BAY IN ABOUT 60 HOURS. THE STRONG HIGH PRESSURE RIDGE OVER THE SOUTHERN PLAINS AND NORTHERN MEXICO SHOULD AMPLIFY AND BECOME MORE MERIDIONAL AS THE U.S. WEST COAST TROUGH LIFTS NORTHWARD OVER THE TOP OF THE RIDGE. THIS SHOULD HELP TO PRECLUDE ANY SIGNIFICANT WESTWARD MOTION AND KEEP THE CYCLONE IN WEAK STEERING FLOW FOR THE NEXT 36 HOURS. AS ANOTHER SHORTWAVE TROUGHS DIGS SOUTHEASTWARD INTO THE SOUTHEAST U.S. LONGWAVE TROUGH...THE CYCLONE SHOULD BE NUDGE SLOWLY NORTHEASTWARD IN 48 TO 72 HOURS. THIS SCENARIO IS CONSISTENT WITH THE CURRENT LONGWAVE TROUGH-RIDGE PATTERN AND THE AVN-GFDL-UKMET MODELS. ALL OF THE GLOBAL MODELS CONTINUE THE TREND OF LIFTING OUT THE UPPER-LEVEL SHORTWAVE TROUGH THAT IS CURRENTLY OVER THE SOUTHEAST U.S... WHICH RESULTS IN A SIGNIFICANT DECREASE IN THE UPPER-LEVEL SHEAR BY 36 HOURS...IF THE CYCLONE REMAINS AT OR NEAR ITS CURRENT LOW LATITUDE. GIVEN THAT NONE OF THE MODELS TAKE THE DEPRESSION MUCH FARTHER NORTH THAN THAN 27N LATITUDE IN 36 HOURS... STRENGTHENING APPEARS LIKELY OWING TO THE DECREASING SHEAR PATTERN. BY 48 HOURS...ANOTHER SHORTWAVE DROPS DOWN TO RE-INFORCE THE UPPER-LEVEL LONGWAVE TROUGH...WHICH RESULTS IN AN INCREASE IN THE JETSTREAM WIND SPEEDS FROM NORTH CAROLINA SOUTHWESTWARD TO NORTH FLORIDA. THE PROXIMITY OF THE CYCLONE TO THE RIGHT-REAR JET ENTRANCE REGION SHOULD ENHANCE THE OUTFLOW AND MASS DIVERGENCE IN THE NORTHERN SEMICIRCLE...WHICH FURTHER SUGGESTS THAT INTENSIFICATION IS PROBABLE. THE OFFICIAL INTENSITY FORECAST IS A LITTLE HIGHER THAN THE SHIPS INTENSITY MODEL BASED ON THE NEAR 30C SSTS THAT THE CYCLONE WILL REMAIN OVER THROUGHOUT THE FORECAST PERIOD. IT SHOULD BE NOTED THAT THE GFDL MODEL BRINGS THIS SYSTEM UP TO 100 KT JUST PRIOR TO ITS FORECAST LANDFALL. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 13/0900Z 25.2N 85.8W 30 KTS 12HR VT 13/1800Z 25.2N 85.9W 35 KTS 24HR VT 14/0600Z 25.6N 86.2W 40 KTS 36HR VT 14/1800Z 26.2N 86.2W 50 KTS 48HR VT 15/0600Z 27.0N 85.8W 65 KTS 72HR VT 16/0600Z 28.5N 83.5W 75 KTS NNNN