Dylan R. Card and Ross A. Lazear
Abstract:
In tornadic supercells, the entrainment of mid-level dry air results in evaporational cooling and the generation of cold downdrafts. Recent research has shown that downdrafts play an important role in the formation and maintenance of tornadoes. Strong, cold downdrafts tend to quickly occlude the tornado's circulation, separating the tornado vortex from the updraft. In order to further examine this effect, tornado cases from Kansas and Oklahoma from 2010 to 2014 were analyzed to see how downdrafts affect tornado strength and path length. Downdraft CAPE (DCAPE) from spatial and temporal proximity soundings was used as the metric for the intensity of the downdrafts in tornadoes rated EF2 and higher. Most DCAPE values fell in a range between 600 and 1600 J kg-1. One expected conclusion was that stronger tornadoes had longer path lengths. Additionally, it was found that long-track tornadoes did not occur at values of DCAPE above 1200 J kg-1. This result is most likely because large values of DCAPE infer strong downdrafts, which would quickly occlude the tornado vortex, greatly limiting the path length and intensity of the tornado. Lastly, it was found that EF2 and stronger tornadoes did not occur at values of DCAPE less than 600 J kg-1, though many EF0 and EF1 tornadoes did, but were removed from the dataset. This relationship is most likely because small values of DCAPE are typically associated with less mid-level dry air and lower mid-level lapse rates.
