Supercell Composite Parameter (SCP)


A multiple component index that is meant to highlight the co-existence of ingredients favoring supercell thunderstorms. The SCP is formulated as follows:

SCP = (muCAPE / 1000 J/kg) * (ESRH / 50 m2/s2) * (EBWD / 10 m/s)

where ESRH = storm-relative helicity for the effective inflow layer using an assumed supercell motion, and the EBWD = effective bulk wind difference over the lower half of the storm depth (effective inflow base to EL height). The EBWD term is capped at a value of 1.5 (e.g., EBWD > 30 m/s is set to 30 m/s), and this same term is set to zero when EBWD < 10 m/s.

The normalization values for each term are based on the work of Thompson et al. (2003) and Thompson et al. (2007).

SCP > 1 favor right-moving (cyclonic in northern hemisphere) supercells, while values of SCP < -1 favor left-moving (anticyclonic) supercells. The Left SCP uses an assumed left supercell motion. More information on left-moving supercell environments can be found in Bunkers (2002) and Edwards et al. (2004).