Non-Supercell Tornado parameter (NST)

The non-supercell tornado parameter (NST) is the normalized product of the following terms:

(0-1 km lapse rate/9 C/km) * (0-3 km MLCAPE/100 J/kg) * ((225 - MLCIN/200) * ((18 - 0-6 km bulk wind difference)/5 m/s) * (surface relative vorticity/8**10-5/s)

This normalized parameter is meant to highlight areas where steep low-level lapse rates correspond with low-level instability, little convective inhibition, weak deep-layer vertical shear, and large cyclonic surface vorticity. Values > 1 suggest an enhanced potential for non-mesocyclone tornadoes.

Please see this for additional information.