Interior Characteristics at Mid-Levels of Thunderstorms in the Southeastern United States

Musil, D.J. and Smith, P.L., 1989. Interior characteristics at mid-levels of thunderstorms in the southeastern United States. Atmos. Res., 24: 149-167. Data characterizing the updraft structures and hydrometeors observed in moderate thunderstorms by the armored T-28 aircraft during the 1986 Cooperative Huntsville Meteorological Experiment (COHMEX) are presented. Updraft regions in the storms were relatively narrow, but usually very turbulent. The vertical winds were generally weak, the peak updraft, speeds usually being <5 ms(-1); the absolute maximum was 19 m s(-1) Cloud liquid-water concentrations measured between the -7.5 degrees C and +5.5 degrees C levels were typically <25% of adiabatic values. Size spectra for the precipitation particles appear truncated, with very high concentrations of particles with sizes between 1 and 5 mm and few larger than 8 mm. Hail occurred in less than 25% of the penetrations, and particles larger than about 1 cm were very infrequent, despite reflectivities often between 50 and 60 dBz. The large numbers of precipitation-size particles usually found in the updraft regions that appeared to be well-mixed indicate that a coalescence mechanism was active in the COHMEX storms. The depth of warm cloud, the generally weak updrafts, and the presence of large cloud droplets all support a coalescence mechanism. Ice processes also must play a role in precipitation development because most COHMEX storms were characterized by extremely deep convection. However, the high concentrations of growth centers observed at T-28 penetration levels suggest that a natural "beneficial competition" process limits the growth of large particles.