Meteorological data below the CNN pictures highlights a few environmental features present during this outbreak. The large-scale pattern featured an upper trough over the southwestern CONUS, with a strong upper-level jet spreading downstream into the Great Plains. This induced cyclogenesis over the high plains, favoring the development of a southerly low-level jet from Texas into Kansas, and aided in establishing a broad moist/unstable warm sector east of the surface dryline. This setting is fairly typical of Great Plains tornado outbreaks. Initially, forecasters believed a substantial tornado threat would develop along the warm front lifting into Nebraska. However, late morning/early afternoon thunderstorms lifted northward across the warm front into Nebraska, and stabilized the airmass, which substantially reduced the potential for tornadoes.
Meanwhile, discrete/isolated supercells developed along the dryline over northwestern Oklahoma and southwestern Kansas. These long-lived storms moved northwest across the region, but struggled to produced tornadoes initially. Near sunset, the low-level jet strengthened to near 70 kt, which dramatically increased low-level vertical wind shear. In addition, the thermodynamic environment continued to favor surface based supercells. The RUC proximity sounding from KEND in northern Oklahoma shows a potent combination of shear and instability present across the area during the early night, with MLCAPE values at or above 2000 J/kg, minimal CINH, and effective SRH values exceeding 700 m2 s-2. Supercells which had been marginal tornado producers during the afternoon suddenly experienced a rapid increase in low-level updraft rotation, resulting in strong to violent tornadoes.
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