Tornado strength and the influence of dissipative heating

In this work, we use a three-dimensional model to investigate if dissipative heating has an influence on simulated tornado strength, particularly for stronger tornadoes once critical wind speeds are reached. Dissipative heating has been implicated in the intensification of hurricanes by several investigators. For hurricanes, simulated horizontal wind speeds need to reach a threshold before there is any dramatic feedback. Once wind speeds do reach a critical strength pressure falls and accompanying horizontal wind speed increases can change by more than 20-30%. Preliminary results suggest that wind speeds less than 70 m/s result in little influence by dissipative heating with tornadoes. At higher wind speeds, dissipative heating has an influence of causing simulated pressure falls and horizontal wind speed increases that can reach approximately 10%. This increase typically is transient with tornadoes, unlike with strong hurricanes. The reason for the transient behavior is that tornadoes are often quite dynamically driven with vortex breakdown readily induced with enhanced lower level pressure falls, which is often associated with reduced mean tangential wind speeds.