Evaluation of the Storm Prediction Center's Day 3 through Day 1 Convective Outlooks

The Storm Prediction Center has been issuing severe weather forecasts, “convective outlooks”, with lead times of up to two days since 2002. This study focuses on the four outlooks valid for the 24-hour period beginning at 1200 UTC: one issued on Day 3, two issued on Day 2, and one issued on Day 1. To evaluate these forecasts the categorical risk areas as well as storm reports are plotted on latitude-longitude grids with 80-km grid spacing. Verification measures such as the critical success index are calculated for each forecast, and are used to examine the skill of each forecast as well as the change in skill among lead times. Additionally, “practically” perfect forecasts – forecasts emulating those made by forecasters given perfect knowledge of the event beforehand – are constructed and evaluated in the same manner as the convective outlooks, allowing for comparisons between the outlooks based on the optimal forecast.