Observational Study of Two Norman, Oklahoma Storms with Very Large, Damaging Hail in Long-Hodograph Environments





Two ≥3-in (7.6-cm) hailstorms affected Norman, Oklahoma in 2021:  one on 28–29 April and the other on 10–11 October.  Wind-driven hail associated with the April storm was estimated to have caused over two million dollars in damage just to county-owned buildings, with estimates of hundreds of millions in damage when including privately owned properties.  The October storm caused further damage in approximately the same locations in Norman as the April storm.  That these storms affected Norman in a single year was unusual, as only three other prior dates had ≥3-in (7.6-cm) hail reports in Norman from 1955–2021.  Radar presentations, surface and upper-air observations, and environmental parameters are presented and intercompared.  The April storm was situated behind a surface boundary, and was mostly sub-severe until it rapidly intensified upon approach to the boundary, while the October storm evolved near a surface boundary and had a history of tornadoes.  A cursory comparison of model-derived and observed proximity soundings for the two 2021 hailstorms with those for the previous six ≥3-in (7.6-cm) hailstorm dates for Cleveland County (in which Norman is located), from 1955–2021, showed that the two 2021 storms had lower environmental buoyancy, but larger deep shear.  This study supports both:  1) the idea that large shear or buoyancy can compensate for lack of the other for the production of significant hail, and 2) the association of long hodographs with large-hail events.