A case study of convectively-induced clear air turbulence

High resolution WRF simulations were used to understand the mechanisms responsible for a case of clear air turbulence that affected two aircraft flying near, but beyond the visible anvil of, a severe convective storm. The storm's outflow extended beyond the satellite-detectable cloudy region into the ostensibly clear air, causing both a decrease in stability and an increase in shear in the surrounding environment. This lowered the Richardson number locally and greatly enhanced the probability of turbulence generation there. The role played by nearby shallower convection is less clear, but it was noted that it is conceivable that two storm anvils can constructively interfere to further decrease the Richardson number in the clearing between them. Further studies of this phenomenon are ongoing.