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Daniel J. Cecil, Kevin R. Quinlan, and Douglas M. Mach

Abstract

On 17 July, intense convection in the eyewall of Hurricane Emily (2005) was observed by the high-altitude (∼20 km) NASA ER-2 aircraft. Analysis of this convection is undertaken using downward-looking radar, passive microwave radiometer, electric field mills, and Geostationary Operational Environmental Satellite-11 (GOES-11) rapid-scan infrared imagery. Radar data show convection reaching more than 17 km, with reflectivity more than 40 dBZ and estimated updraft speeds greater than 20 m s−1 at ∼14-km altitude. All of the passive microwave frequencies (10, 19, 37, and 85 GHz) experienced scattering by large ice particles. Large electric fields with dozens of lightning flashes were recorded. Because of safety concerns arising from difficulties with the first two transects, the flight plan was modified to avoid passing above the eyewall again. These observations occurred 8–10 h after Emily’s peak 929-hPa intensity, with central pressures from reconnaissance aircraft having risen to 943 hPa immediately before the flight and 946 hPa immediately afterward (no such measurements available during the flight). Rapid-scan infrared imagery reveals that a period of episodic bursts of strong, deep convection was beginning just as the ER-2 arrived. The first leg across the eye coincided with a rapidly growing new cell along the flight track in the western eyewall. This strong convection may have been characteristic of Emily for the ∼24 h leading up to landfall in the Yucatan, but it does not appear to be a continuation of convective trends from the previous rapid intensification or peak intensity periods.

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