Microphysical Characteristics of a Well-Developed Weak Echo Region in a High Plains Supercell Thunderstorm

Microphysical measurements in and near the weak echo region of a supercell thunderstorm are discussed. The observations were made in southeastern Montana with an armored T-28 aircraft, which has the capability to measure hydrometeors over almost the entire spectrum between about 3 μm and 5 cm diameter. The storm exhibited many of the classic supercell characteristics, such as a well-developed weak echo region, overhang, persistent hook echo, and a large high-reflectivity core. Peak updrafts in the weak echo region exceeded 50 m s−1, and a continuous region of updraft extending over a horizontal distance of more than 14 km was observed. The updraft core appeared to be undiluted, but the edges of the updraft were clearly mixed with air from other regions of the storm. Virtually no ice particles were observed in the weak echo region, but the cloud liquid water concentrations exceeded 6 g m−3. Hail larger than 4 cm was encountered in several locations to the west of the weak echo region. The observations suggested that the hail achieved most of its growth at levels above the T-28, became large enough to descend in the edge of the updraft, and depleted the cloud liquid during the descent.