Positive Cloud-to-Ground Lightning in Tornadic Storms and Hailstorms

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Abstract
Although negative ground flashes usually dominate cloud-to-ground lightning activity, positive ground flashes can dominate in some severe storms for periods ranging from 30 min to several hours. Unlike most other types of storms in which positive ground flashes occur, severe storms can have positive flash rates and densities of strike points comparable to those usually observed for negative ground flashes in active thunderstorms. Fifteen such storms are analyzed in this paper to examine relationships of positive ground flashes to various storm characteristics, especially reports of large hail and tornadoes. In 4 of the 15 storms, ground flash activity was dominated by positive cloud-to-ground lightning throughout most of the life of the storm. In 11 storms, the dominant polarity of ground flashes switched from positive to negative sometime during the mature stage of the storm. In all cases observed by Doppler radar, storms dominated by positive flashes had at least some rotation, and in most case... Abstract Although negative ground flashes usually dominate cloud-to-ground lightning activity, positive ground flashes can dominate in some severe storms for periods ranging from 30 min to several hours. Unlike most other types of storms in which positive ground flashes occur, severe storms can have positive flash rates and densities of strike points comparable to those usually observed for negative ground flashes in active thunderstorms. Fifteen such storms are analyzed in this paper to examine relationships of positive ground flashes to various storm characteristics, especially reports of large hail and tornadoes. In 4 of the 15 storms, ground flash activity was dominated by positive cloud-to-ground lightning throughout most of the life of the storm. In 11 storms, the dominant polarity of ground flashes switched from positive to negative sometime during the mature stage of the storm. In all cases observed by Doppler radar, storms dominated by positive flashes had at least some rotation, and in most case...

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