Climatology of the Supercell Composite Parameter (1979 – 2004)

The Storm Prediction Center uses “ingredients-based” indices as one part of severe storm prediction and one of the indices is named the Supercell Composite Parameter. The Supercell Composite Parameter (SCP) is a multi-component index that includes CAPE, storm relative helicity, and deep layer vertical wind shear. Each SCP component is normalized to "threshold" values determined to be favorable for supercell storms, and the product of these three normalized components forms the SCP. With the availability of 32km resolution North American Regional Reanalysis data, a 26-year climatology of the SCP at 00 UTC was developed in order to view daily, monthly, and seasonal variations in the SCP across the continental U.S. The SCP was investigated quantitatively by the number of days that the values were greater than or equal to one at a gridpoint during each month of the year. The central plains were found to have the highest number of days with environments supportive of supercells.