EF1 tornado in Adair County, Oklahoma

This is the first segment of a two-segment tornado. This tornado uprooted numerous trees, destroyed several outbuildings, and damaged the roofs of several homes. Based on this damage, maximum estimated wind in this segment of the tornado was 90 to 100 mph. The tornado continued into Benton County.

Thunderstorms developed over central Oklahoma during the early evening of the 20th, along and just ahead of a cold front moving into the area. The atmosphere ahead of the front was very unstable. Wind fields across the region strengthened with the approach of a strong upper level storm system, and very strong deep layer shear developed over eastern Oklahoma by the evening. The combination of strong instability and very strong wind shear promoted the development of supercell thunderstorms, that produced hail up to baseball size and damaging wind. As the thunderstorms moved eastward during the late evening, they eventually organized into a solid line of thunderstorms. Low level wind shear increased across the region during the evening, and this supported the development of several tornadoes, in addition to the very strong downburst wind that some of the thunderstorms produced.