Potential Use of a Storm-Related Weather Radar Signature in Severe Weather Warning Decisions

What is it about?

After the dual-polarization upgrade, new radar signatures are now available to National Weather Service forecasters, but there is uncertainty about how these signatures can be explicitly used to issue severe weather warnings. This paper examines 42 storms in Oklahoma to explore one such signature known as a Zdr column, which can give information about the location and intensity of a storm's updraft. Topics covered include: typical values of Zdr column depth, relationships between Zdr columns and storm reports, relationships between Zdr columns and other radar signatures forecasters typically use to issue warnings, and the impact of radar update time on observing Zdr columns.

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Photo by Michael Weidner on Unsplash

Photo by Michael Weidner on Unsplash

Why is it important?

Previous work has suggested that dual-polarization radar signatures may be helpful to forecasters in terms of issuing warnings for severe weather. This work aims to extend that idea by linking one such radar signature to the warning decision process. Significant findings include: 1) statistically significant differences exist between the Zdr column depth and -20C reflectivity core intensity of severe and nonsevere storms, 2) Zdr columns evolve several minutes earlier than -20C reflectivity cores and could therefore give forecasters additional time to examine a storm and potentially increase warning lead time, and 3) rapid-update radar data provides a clearer and earlier picture of storm evolution and can therefore also help forecasters extend warning lead time.

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