Weather Flashback

August 2021 - A Rare August Supercell (August 14, 2018)


I captured this scene on the afternoon of 14 August 2018 along Highway 9 in Norman, Oklahoma (Oklahoma's "Research Corridor", no less). On this day, a supercell thunderstorm erupted west of Norman and propagated towards the north and east. While supercell thunderstorms are not an uncommon occurrence in "tornado alley" from year to year, this type of thunderstorm rarely occurs in summertime here. This is not the case in other parts of the United States like the northern Plains and upper Midwest, where supercell thunderstorm occurrence tends to peak in summertime. In principle, the rarity of summertime supercell thunderstorms in the southern Plains region is due to the tendency for weaker vertical wind shear during summer here versus other seasons. The weaker vertical shear here is mostly due to weaker horizontal temperature gradients near the surface in the region during summer versus other seasons. However, occasionally, a supercell thunderstorm will develop in summertime in the southern Plains region. This sort of development was the case on this particular afternoon, where vertical wind shear was only marginally supportive of storm-splitting; yet buoyancy profiles in the area remained favorable for continued, vigorous updraft development. The culmination was a thunderstorm was transient supercell characteristics, as buoyant updrafts interact with at least marginally supportive supercell vertical wind shear profiles. However, surely there is more to unravel here than a (simple) comparison of buoyancy to vertical wind shear, eh?

Plate 1. A Rare August Supercell. Captured on August 14, 2018 at 5:32pm CDT. Looking northwest from 35.19°, -97.46°.