Conditional Intensity Estimation of Tornadoes using Environmental Parameters

The majority of societal impacts from tornadoes typically come from the strongest (i.e., F/EF3+) tornadoes even though they account for less than 5% of all documented tornadoes. The current operational intensity forecasts for tornadoes are issued as part of the NOAA/NWS/Storm Prediction Center (SPC) Convective Outlooks. These tornado intensity forecasts simply consist of one probabilistic contour representing the unconditional 10% probability of a significant tornado (i.e., F/EF2+) within 25 miles of a point. To allow for more flexibility and specificity in tornado intensity forecasts, SPC is proposing to move toward a conditional intensity framework. This study shows that the environment has considerable control on the conditional intensity distribution of tornadoes, especially from November through May. In fact, an 18-year sample of thousands of tornado grid hours shows a strong positive correlation between the significant tornado parameter (STP) and the conditional probability of F/EF2, F/EF3, and F/EF4+ tornadoes. These results showing the relationship between the environment and conditional intensity of tornadoes will be presented along with the implications this information has on a future operational conditional intensity forecast framework at SPC.