Preliminary Doppler Velocity Measurements in a Developing Radar Hook Echo

Abstract

Single Doppler radar measurements were made in a squall line that formed in southern Kansas during the afternoon of 2 June 1971 and moved south-southeastward through central Oklahoma. During the period of data collection, a pronounced hook echo, having at least one funnel cloud associated with it, developed. Preliminary analyses of these first Doppler velocity measurements within a radar hook echo in the tornado belt are presented.

NSSL Dual-Doppler Radar Measurements in Tornadic Storms: a Preview

“…In 1967, the National Severe Storms Laboratory (NSSL) first applied dual-Doppler radars to thunderstorm studies. During the 1967 spring, NSSL brought Cornell Aeronautical Laboratory's 3 cm Doppler radar to Oklahoma for an operation with its own 3 cm Doppler radar (Brown and Peace, 1968). The second application (1969) of two Doppler radars to study thunderstorms took place in Colorado with the Wave Propagation Laboratory's (WPL) 3 cm Doppler radars (Lhermitte, 1970).…”

“…Since 10 cm wavelength is not subject to excessive attenuation and since velocity discrimination capability is proportional to wavelength, NSSL began the fabrication of a 10 cm Doppler radar in the late 1960s. Spring data collection began in 1971 (Brown et al, 1971).…”

Doppler Radar Observations of the Brookline, Massachusetts Tornado of August

“…The velocity patterns at 3° and 4° elevation angles (not shown) were similar to the pattern at 2°. Donaldson et al (1969), Kraus (1970), Brown et al (1971), and Crawford and Brown (1972) all describe this pattern in other storms and postulate that it represents a mesoscale vortex as discerned by a single Doppler radar seeing only radial components of velocity. Donaldson (1970) provides quantitative criteria for validating this assumption.…”

“…For several years, horizontal motions within severe thunderstorms have been observed by Doppler radars. Techniques using single Doppler radars scanning in azimuth at low elevation angles have resulted in several observations showing pictures of radial velocity flow patterns in New England (Donaldson et al, 1969;Kraus, 1970) and in Oklahoma (Brown et al, 1971;Crawford and Brown, 1972). The velocity patterns in New England were rather similar to those in Oklahoma.…”

Articles

“…Weather radar is the primary tool used by warning forecasters to identify areas of potential tornado development. Radar reflectivity provides forecasters with a clear view of tornadic features, such as the hook echo (Markowski 2002), and Doppler radial velocity shows horizontal wind shear, sometimes an early indicator of tornado formation (Brown et al 1971). Radar polarimetric data provide storm microphysical information, such as hydrometeor type and shape, that can be used to identify areas of significant low-level wind shear (referred to as Z DR arcs) and tornado debris (Ryzhkov et al 2005;Bodine et al 2013).…”