Research continues to increase on radar and environmental aspects of the NMT process which is mainly achieved through the stretching of ambient vertical vorticity. Modeling and observational studies suggest NMT typically occurs with convective updrafts in weak wind shear environments characterized by steep low-level lapse rates and strong low-level instability. Further, these updrafts generate along slow-moving or stationary surface boundaries possessing strong horizontal shears with misoscale vorticies (Wakimoto and Wilson 1989; Brady and Szoke 1989; Lee and Wilhelmson 1997, 2000; and Davies 2003).
NMT environmental diagnosis attempts have been made by Davies (2003) by parameterizing the higher low-level lapse rate and higher low-level convective instability (e.g., enhanced stretching potential) along such boundaries. In an effort to further increase situational awareness in the operational forecast environment, a parameter was designed in spring 2005 to build on work by Davies (2003) and others described above by incorporating a measure of deep shear (0-6km bulk shear), low-level convective instability (0-3km ML CAPE), low-level lapse rate (0-1km), convective inhibition (ML CIN), and surface relative vorticity. Surface relative vorticity was included as a measure of the ambient vertical vorticity available to convective updrafts along a surface boundary (e.g., as a proxy to misoscale vorticity presence).
A review of the parameter construct, its application through case examples, and behaviors of the parameter will be presented. Limitations of the parameter, such as false alarms, will also be clearly addressed. The preliminary datasets collected suggest the parameter can provide a positive contribution toward increased forecaster situational awareness in environments favorable for non-mesocyclone tornadogenesis.