Prior studies have shown that updraft overturning efficiency increases as the depth of the moist layer increases. In environments having subcloud equivalent potential temperature and other key parameters similar to the first environment above, but having a moist layer depth and level of free convection equal to 1.6 km, storm peak updrafts were found to reach 54 m/s. Reducing the temperatures of these environments by 8.0 C allows the peak updraft speeds to grow to 70 m/s, a value that, because of the release of the latent heat of fusion, actually exceeds the maximum expected from basic parcel theory.
The increases in peak updraft speeds occurring in association with decreasing environmental temperatures are the result of reductions in condensate loading in the cooler environments. This is shown also by the reduced precipitation mixing ratios in the storms there. Condensate loading is related to precipitable water content, which is about 60 mm for our warm, moist environments, and about half that value in our cooler environments. Such values roughly bracket those commonly encountered in many actual severe weather environments. The trends seen in the simulations suggest that, for otherwise similar mixed and moist layer depths and similar amounts and vertical distributions of instability and shear, convective storms in the relatively cool environments of the U. S. High Plains should have more intense updrafts than those occurring in warmer environments. These conclusions remain unchanged even if reasonable allowances are made for the effects of the reduced surface pressures found on the High Plains.
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