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Structure of an Evolving Hailstorm, Part III: Internal Structure from Doppler Radar

R. G. StrauchNOAA/ERL/Wave Propagation Laboratory, Boulder, Colo. 80303

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F. H. MerremNOAA/ERL/Wave Propagation Laboratory, Boulder, Colo. 80303

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Abstract

Two X-hand Doppler radars observed a hailstorm that passed directly over one of the radars during the 1973 National Hail Research Experiment (NHRE). While one of the radars scanned the storm at low elevation angles the other radar, which operated simultaneously in a zenith–pointing mode, measured part of an updraft. Observations by other NHRE participants assisted in interpreting the radial velocity fields so that inflow and outflow could be identified from the scanning radar measurements. The peak updrafts occurred just ahead of. the highest reflectivity while the strongest downdrafts were found only 6 km behind the updraft. Strong turbulence was generated in the transition region between updraft and downdraft as evidenced by large velocity variances. A substantial part of the downdraft appeared to have been led by air that had ascended in the updraft. Low–level velocity fields were in general agreement with surface measurements and showed the outflow toward the front of the storm in the gust front as well as outflow opposite the echo motion behind the storm. There was strong outflow opposite the direction of echo motion at the top of the storm which agreed with photographs of the anvil overhang.

Abstract

Two X-hand Doppler radars observed a hailstorm that passed directly over one of the radars during the 1973 National Hail Research Experiment (NHRE). While one of the radars scanned the storm at low elevation angles the other radar, which operated simultaneously in a zenith–pointing mode, measured part of an updraft. Observations by other NHRE participants assisted in interpreting the radial velocity fields so that inflow and outflow could be identified from the scanning radar measurements. The peak updrafts occurred just ahead of. the highest reflectivity while the strongest downdrafts were found only 6 km behind the updraft. Strong turbulence was generated in the transition region between updraft and downdraft as evidenced by large velocity variances. A substantial part of the downdraft appeared to have been led by air that had ascended in the updraft. Low–level velocity fields were in general agreement with surface measurements and showed the outflow toward the front of the storm in the gust front as well as outflow opposite the echo motion behind the storm. There was strong outflow opposite the direction of echo motion at the top of the storm which agreed with photographs of the anvil overhang.

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