Significant Tornado Parameter (STP)
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).