Dynamical processes associated with winter lightning events in Iowa

Date

2021-05

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Abstract

Winter lightning is an unusual weather phenomenon in which lightning is concurrent with wintry precipitation. Forecast guidance for winter lightning events is limited in part by the understanding of the driving dynamics. Two forms of ascent in synoptic systems are upright and slantwise convection. A large archive of data from the Iowa Environmental Mesonet was used to look at six years of surface temperature and thunder reports, as well as summary maps of ground strike data. A survey of radar data showed both cellular and banded precipitation during these cold thunder events. RAP mesoscale forecast data was used to assess which type(s) of instability were associated with the winter lightning reports. Using National Lightning Detection Network, flash characteristics were investigated for all thundersnow events around locations of communication towers. All cellular events had moderate to high amounts of gravitational instability. In general, banded thundersnow events occurred with inertial instability or where frontogenesis occurred in a region of weak symmetric instability. Conditional Symmetric Instability was often present with each thundersnow event, but rarely was found in the absence of gravitational or inertial instability. Events where Conditional Symmetric Instability was present with little to no gravitational or inertial instability present had little lightning activity. Flashes for cellular events did not have a preference of location whereas a high percentage of flashes for banded events were at a tower location.

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Keywords

Winter, Thunderstorms, Instability, Tower Lightning, Banded Convection, Cellular Convection

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