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| #9310 (Received by flhurricane at: 10:50 PM 19.Sep.2004) TCDAT1 TROPICAL STORM JEANNE DISCUSSION NUMBER 26 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT SUN SEP 19 2004 A NOAA HURRICANE HUNTER FOUND 60 KT FLIGHT-LEVEL WINDS AT 925 MB ABOUT 25 N MI FROM THE CENTER IN BOTH THE NORTHEASTERN AND SOUTHEASTERN QUADRANTS...ALONG WITH A CENTRAL PRESSURE OF 994 MB. SURFACE WINDS FROM THE STEPPED FREQUENCY MICROWAVE RADIOMETER ON THE AIRCRAFT WERE NEAR 50 KT. THE INITIAL INTENSITY IS THUS INCREASED TO 50 KT. WHILE CONVECTIVE BANDING HAS INCREASED AND MOVED CLOSER TO THE CENTER SINCE YESTERDAY...THE STORM IS STILL NOT THAT WELL ORGANIZED AS REFLECTED IN SATELLITE INTENSITY ESTIMATES OF 35 KT. CIRRUS OUTFLOW IS POOR IN THE SOUTHERN QUADRANT AND FAIR TO GOOD ELSEWHERE. THE INITIAL MOTION IS 010/7...ALTHOUGH THE MOTION DURING THE NOAA FLIGHT WAS CLOSER TO 030/7. JEANNE IS CURRENTLY BETWEEN A DEEP LAYER RIDGE TO THE EAST AND AN UPPER-LEVEL TROUGH/COLD FRONT TO THE NORTHWEST. TRACK GUIDANCE AGREES THIS PATTERN SHOULD GRADUALLY TURN JEANNE NORTHEASTWARD THROUGH 36 HR. SERIOUS MODEL DIVERGENCE THEN ARISES. THE GFS AND GUIDANCE BASED ON IT...INCLUDING THE GFDL...MARCH JEANNE STEADILY TOWARD THE EAST OR EAST-NORTHEAST SOUTH OF A STRONG DEEP-LAYER TROUGH THROUGH 120 HR...WITH THE GFS SHOWING JEANNE FOLLOW KARL NORTHEASTWARD TO HIGHER LATITUDES. ON THE OTHER HAND...THE UKMET AND NOGAPS TURN JEANNE SOUTHEASTWARD AND SOUTHWARD THROUGH ABOUT 96 HR AS KARL PASSES TO THE EAST AND A DEEP-LAYER RIDGE BUILDS TO THE NORTHWEST...THEN MOVE IT NORTHWEST AS THE RIDGE WEAKENS. AT THE MOMENT...IT CANNOT BE DETERMINED WHICH OF THESE TWO OPTIONS WILL VERIFY. THEREFORE...THE OFFICIAL FORECAST TRACK SPLITS THE DIFFERENCE BETWEEN THE TWO EXTREMES AND CALL FOR A SLOW EASTWARD DRIFT AFTER 36 HR. THIS CONTINUES TO BE A LOW CONFIDENCE FORECAST. THE INTENSITY FORECAST REMAINS PROBLEMATIC. FOR NOW...THE UPPER- LEVEL WINDS ARE FAVORABLE AND THE BROAD CIRCULATION SHOULD GRADUALLY CONSOLIDATE. AFTER 24-36 HR...THE GFS AND THE NOGAPS INDICATE SIGNIFICANT UPPER-LEVEL WESTERLIES IMPACTING JEANNE. DESPITE SHOWING MORE THAN 20 KT OF SHEAR...THE SHIPS MODEL CALLS FOR STRENGTHENING DURING THIS PERIOD AS DOES THE GFDL. ANOTHER COMPLICATION IS THAT THE COLD FRONT MAY INTERACT WITH JEANNE IN ABOUT 36 HR. THE INTENSITY FORECAST CALLS FOR STRENGTHENING TO 70 KT BY 48 HR...WHICH IS LESS THAN THE 78 KT FROM SHIPS OR THE 86 KT FROM THE GFDL. AFTER 48 HR...THE ENVIRONMENT WILL LIKELY BECOME HOSTILE ENOUGH TO STOP INTENSIFICATION AND CAUSE SLIGHT WEAKENING. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 20/0300Z 25.2N 72.0W 50 KT 12HR VT 20/1200Z 26.2N 71.7W 55 KT 24HR VT 21/0000Z 27.0N 71.0W 60 KT 36HR VT 21/1200Z 27.3N 70.0W 65 KT 48HR VT 22/0000Z 27.0N 69.0W 70 KT 72HR VT 23/0000Z 26.5N 68.5W 70 KT 96HR VT 24/0000Z 26.5N 68.0W 65 KT 120HR VT 25/0000Z 27.0N 67.5W 60 KT |
