High-resolution dual-doppler analyses of the eyewall in an intense hurricane

On 21 and 22 August, 1999, the Hurricane Research Division of the National Oceanographic and Atmospheric Administration (NOAA) conducted two single-plane experiments in Hurricane Bret with P-3 aircraft from NOAA's Aircraft Operations Center (AOC). The flight pattern on the 21st was intended to survey the vortex and it's environment; at this time Bret was a Category 4 hurricane, with winds > 63m/s. The flight on the 22nd occurred as Bret, now a Category 3 storm with winds still > 50 m/s, made landfall on the South Texas coast between Corpus Christi and Brownsville.

On both days there was a module where the aircraft flew upwind inside the eye, at 4200 m altitude just inward from the eyewall. Because of the outward slope of the eyewall, GPS sondes were deployed such that they sampled the wind maxima at lower altitudes, finding winds > 74 m/s on the 21st, and > 60 m/s on the 22nd.

The tail Doppler radar was operated in Fore/Aft Scanning mode during both flights. Usually in hurricane penetrations we only get a few eyewall slices as the aircraft quickly crosses the eye, but during the eye circles many slices were collected at close range (<5 km) that will provide a detailed picture of the three-dimensional windfield in a portion of the eyewall on successive days. We will present the dual-Doppler windfields at the conference and a companion paper (Black et al) will combine the radar data with the GPS sonde data to provide further details of the low level wind maxima.