Observations of a Colorado Tornado. Part II: Combined Photogrammetric and Doppler Radar Analysis

Abstract

An integrated analysis of photographic and Doppler radar observations of a tornadic storm during the Convection Initiation and Downburst Experiment (CINDE) is presented. High-resolution single-Doppler radar measurements are combined with cloud photogrammetry to reveal the detailed structural relationship of the hook echo and the misocyclone with visual features of the tornado. Vertical cross sections of dual-Doppler winds in the plane of the photographs were also examined to determine the complex motions within and surrounding the vortex. The tornado was found to be within a weak-echo hole of the hook echo. The hole progressed upward above cloud base as the tornado matured. An annulus of higher reflectivity that formed a book echo is hypothesized to have been composed of sparse but large raindrops. The airflow fields suggest that vortex breakdown and axial downdrafts were present near the ground at early stages shortly after the tornado became visible. Later, axial upward flow dominated at all levels until the collapse of the vortex.