A multiple component index that is meant to highlight the co-existence of ingredients favoring right-moving supercells capable of producing F2-F5 tornadoes. The STP is formulated as follows:

Sig Tor (CIN) = (mlCAPE / 1500 J/kg) * (ESRH / 150 m2/s2) * (EBWD / 12 m/s) * ((2000 - mlLCL) / 1000) * ((mlCINH + 200) / 150)

where "ml" denotes the lowest 100 mb mean parcel, ESRH = the effective storm-relative helicity, EBWD = the 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 as in the Supercell Composite Parameter, though the minumum value is raised to 12 m/s. The mlLCL term is set to 1 for mlLCL heights < 1000 m AGL, and the mlCINH is set to 1 for mlCINH values > -50 J/kg.

The "Sig Tor (fixed)" is similar to the "sig Tor (CIN)", except that mlCAPE is replace with sbCAPE (surface parcel), ESRH is replaced with 0-1 km SRH, the EBWD is replaced with 0-6 km bulk wind difference, and the CINH term is dropped.

For additional information, see Thompson et al. (2004).