Internal Structure of a Small Mesoscale Convective System

This paper utilizes experimental data from a multiple Doppler radar and surface mesoscale network to describe the evolution and structure of a small, isolated, mesoscale convective system over the South Park region of central Colorado. This system evolved from a cluster of convective clouds which eventually transformed to a mature system possessing both stratiform and convective components. The structure of individual precipitating convective clouds comprising the mature system depended on their location (upshear or downshear) relative to the system. Unsteady upshear convective components formed discretely and propagated upshear. In contrast, downshear convective components occupied a greater area, exhibited more steadiness, and propagated downshear. Doppler analyses indicate that mesoscale updrafts within anvils flanking the convective cores existed relatively early, about 1.5 h after first cloud formation. Mesoscale downdrafts did not appear until ∼3 h after precipitation initiation. The appearance of a mesoscale downdraft was temporally correlated with intensification of the upshear convective region. The analyses suggest a close dependence between upshear convection and the stratiform region in this case. Upshear convection supplied condensate to the stratiform region, while the stratiform region produced mesoscale downdrafts whose outflow boundary helped maintain the upshear convection.