Finescale Radar Observations of the 22 May 2002 Dryline during the International H2O Project (IHOP)

Abstract

The dryline has long been associated with the development of severe thunderstorms in the southern plains during the spring and early summer months. The propagation and structure of the dryline are closely tied to surface processes that are neither well understood nor well resolved with current observational capabilities. As a result, there are often large errors in forecasts of dryline position and structure. Improvements in radar technology have allowed for better observations of the dryline in recent years. Here, very finescale radar observations taken with the University of Massachusetts?Amherst (UMass) mobile W-band radar during an International H2O Project (IHOP) double-dryline event on 22 May 2002 in the Oklahoma panhandle are presented. The observations are placed in the context of the dryline secondary circulation, which describes flow in a plane normal to the dryline. The narrow, half-power beamwidth of the antenna on the W band (0.18°) permitted the measurements of channels of upward (8?9 m s?1 over a horizontal distance of 50?100 m) and downward vertical velocity, greater in absolute magnitude than that previously reported in dryline field studies. A ground-based variational pseudo-multiple-Doppler processing technique is introduced, which is used to decompose time series of RHI velocity data into horizontal and vertical wind components. The technique is applied to a retrograding dryline from 22 May 2002. Finescale structure of the retreating dryline interface is presented.