Quantitative Verification of Storm Prediction Center 1300 UTC Tornado Outlooks

Storm Prediction Center (SPC) Convective Outlooks provide severe weather researchers, storm observers, spotters, and the public with reliable severe weather forecasts on a daily basis. These Outlooks display geographical areas that are likely to be impacted by tornadoes, large hail, and damaging winds, as well as a general categorical severe weather risk. All 1300 UTC Outlooks that included a forecast of a 10% or greater chance of tornadoes within 25 miles of a point, issued between 1 January 2009 and 31 December 2016, were selected for further examination in this study. Each tornado risk percentage on an Outlook was examined by plotting the Outlook and the tornado tracks from a given day using Python. If the fraction of an area within 25 miles of tornado tracks was close to the forecast percentage issued for that area, that portion of the Outlook verified. If this was not the case, then that portion of the Outlook did not verify. The use of a quantitative threshold in this work builds upon past work in which the verification was determined qualitatively.

Outlooks were further examined using radar and satellite imagery, surface observations, upper-air data, and archived mesoscale analysis. Values of common severe weather variables, such as storm-relative helicity, lifting condensation level, and shear vector orientation relative to the initiating boundary were collected. Data from successful forecasts will be contrasted with data from unsuccessful forecasts in hopes of guiding additional research that can be used to improve future forecasts.