Forecaster's forum: Subjective Tornado probability forecasts in severe weather watches

Abstract

An experiment was conducted at the storm Prediction Center (SPC) to assess the accuracy of subjective probability forecasts for tornadoes within individual convective watch areas. Probability forecasts for one or more and three or more tornadoes were produced for 166 severe weather watches during 1997 and 1998. Categorical forecasts of maximum tornado intensity, as indicated by F-scale damage ratings, were also performed. The probability and intensity forecasts were made in an operational setting prior to the issuance of each watch to stimulate the decision making process that might be employed if the SPC were to begin including probabilities in their watch products. Results indicate considerable skill in forecasting tornado probabilities, though the maximum intensity forecasts were not particularly accurate. It is hypothesized that accurate tornado intensity forecasts will be difficult to achieve until storm-scale processes are more fully understood.