A portion of an ongoing CSTAR project between NC State University and the NWS is intended to improve the understanding of High Shear Low CAPE (HSLC) severe weather events in the Southeast. Project participants from the NWS include 11 Weather Forecast Offices (WFOs) in the Southeast along with the Storm Prediction Center.
One item that WFO forecasters have noted when examining past events was that the highly relied upon SPC meosanalysis products of CAPE did not provide the desired level of detail on the lower end of the CAPE analysis. For HSLC severe weather events, CAPE values can range on the order of just a few hundred J/kg and the addition of a lower end CAPE contour or two would provide a great benefit to forecasters.
Based on input from collaborators at the WFOs, the SPC has made changes to the contour setup for the Surface-Based CAPE (SBCAPE), Mixed-Layer CAPE (MLCAPE), and the Most-Unstable CAPE (MUCAPE) analysis which will result in an additional contour at either 100 J/kg or 250 J/Kg along with the existing contours at 500 J/Kg, 1000 J/Kg, etc.
It is expected that these new contours will provide forecasters with a better approximation of the amount of CAPE in these low CAPE severe weather events. An example of the new contours at 100 and 250 J/Kg is shown below in the SPC mesoanalysis of SBCAPE and SBCIN from 16 UTC on 4 August 2011.