The SWDVs are evaluated by identifying the grid points for which a predetermined magnitude is equaled or exceeded. For each of these grid points, if a selected PP probability is equaled or exceeded, a hit is counted. Otherwise, the grid point is counted as a false alarm. For each grid point in which the SWDV magnitude is below the selected threshold, if the selected PP probability is equaled or exceeded, a miss is counted. Otherwise, the grid point is counted as a correct null. Contingency statistics are computed for various combinations of SWDV magnitudes and PP probabilities. This technique provides insight into the PP probability for which a given SWDV magnitude has maximum accuracy or skill.
Preliminary findings suggest (1) several SWDVs exhibit considerable skill in identifying locations with >0.01 PP probabilities of severe weather of any type or of a specific type, (2) in general, skill decreases with increasing PP probability and increasing SWDV magnitude, (3) skill decreases with increasing temporal resolution, (4) skill is lower for unconditional PP probabilities, particularly for single severe weather report types, owing to an increased number of false alarms, and (5) most SWDVs are highly correlated, resulting in statistically similar accuracy and skill in identifying PP probability exceedance regions.