ZCZC MIATCDAT5 ALL TTAA00 KNHC DDHHMM HURRICANE HUMBERTO DISCUSSION NUMBER 11 NATIONAL WEATHER SERVICE MIAMI FL 11 PM EDT SUN SEP 23 2001 OBSERVATIONS FROM A MULTI-AIRCRAFT RESEARCH MISSION...CAMEX... INDICATE THAT HUMBERTO HAS STRENGTHENED FURTHER. EYEWALL DROPSONDE DATA FROM A NOAA AIRCRAFT SHOWED AN 87 KNOT WIND SPEED AT THE SURFACE IN THE NORTHEAST QUADRANT. THERE WERE ALSO SURFACE WIND MEASUREMENTS OF ABOUT THE SAME MAGNITUDE BY THE STEPPED FREQUENCY MICROWAVE RADIOMETER...SFMR...INSTRUMENT ON BOARD THE AIRCRAFT. LOWER LAYER AVERAGE WINDS FROM THE DROPSONDES YIELDED A SOMEWHAT LOWER WIND SPEED...BUT MAY BE BIASED BY THE VERTICAL TILT OF THE EYEWALL. THEREFORE THE CURRENT INTENSITY IS ESTIMATED TO BE 85 KNOTS. THE CENTRAL PRESSURE...983 MB...WOULD NOT NORMALLY SUPPORT SUCH STRENGTH. HOWEVER HUMBERTO IS EMBEDDED IN A HIGHER-THAN-NORMAL SEA LEVEL PRESSURE ENVIRONMENT...WHICH IS LIKELY ENHANCING THE GRADIENT. THE HURRICANE HAS PROBABLY REACHED ITS PEAK INTENSITY. THERE ARE STRONG HIGH-LEVEL WESTERLIES TO THE NORTH OF THE SYSTEM AND THESE WESTERLIES SHOULD SOON CAUSE A SUBSTANTIAL INCREASE IN VERTICAL SHEAR. SINCE THE ENVIRONMENT IN HUMBERTO'S PATH SEEMS SO UNFAVORABLE...THE FORECASTED WEAKENING IS AT A LITTLE GREATER RATE THAN THAT SHOWN BY THE SHIPS GUIDANCE INITIAL MOTION IS JUST SLIGHTLY EAST OF DUE NORTH...010/9. THE FLOW AHEAD OF A DEEPENING 500 MB TROUGH OVER THE EASTERN U.S. SHOULD CARRY HUMBERTO ON A NORTH TO NORTHEASTWARD TRACK OVER THE NEXT COUPLE OF DAYS. NEAR THE END OF THE PERIOD...THE SYSTEM SHOULD ENCOUNTER FASTER AND MORE ZONAL STEERING FLOW IN THE MID-LATITUDE WESTERLIES...SO HUMBERTO SHOULD BEGIN ACCELERATING EASTWARD BY THAT TIME. THE OFFICIAL FORECAST TRACK IS BENT A LITTLE MORE TO THE RIGHT OF THE PREVIOUS FORECAST...IN LINE WITH THE LATEST NCEP GLOBAL MODEL GUIDANCE. FORECASTER PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 24/0300Z 33.2N 67.0W 85 KTS 12HR VT 24/1200Z 34.5N 66.8W 80 KTS 24HR VT 25/0000Z 36.5N 66.4W 75 KTS 36HR VT 25/1200Z 38.6N 65.4W 70 KTS 48HR VT 26/0000Z 40.5N 63.5W 65 KTS 72HR VT 27/0000Z 43.0N 56.0W 55 KTS NNNN