Help - Violent Tornado Parameter

Violent Tornado Parameter

A multiple ingredient, composite index that includes effective bulk wind difference (EBWD), effective storm-relative helicity (ESRH), 100-mb mean parcel CAPE (mlCAPE), 100-mb mean parcel CIN (mlCIN), and 100-mb mean parcel LCL height (mlLCL), 0-3 km mean parcel CAPE and 0-3 km lapse rates.

The index is formulated as follows:

VTP = (mlCAPE/1500 J kg^-1) * ((2000-mlLCL)/1000 m) * (ESRH/150 m² s^-2) * (EBWD/20 m s^-1) * ((200+mlCIN)/150 J kg^-1) * (0-3 km MLCAPE/50 J kg^-1) * (0-3 km Lapse Rate/6.5 ℃ km^-1)

The 0-3 km lapse rate term is set to 2.0 when 0-3 km MLCAPE > 100 J kg^-1. Like STP, the mlLCL term is set to 1.0 when mlLCL < 1000 m, and set to 0.0 when mlLCL > 2000 m; the mlCIN term is set to 1.0 when mlCIN > -50 J kg^-1, and set to 0.0 when mlCIN < -200; the EBWD term is capped at a value of 1.5 for EBWD > 30 m s^-1, and set to 0.0 when EBWD < 12.5 m s^-1. Lastly, the entire index is set to 0.0 when the effective inflow base is above the ground.

Research using observed soundings found that 0-3 km CAPE and 0-3 km lapse rate were notable discriminators of violent tornado environments (verses weak and/or significant tornado environments). These parameters were combined into the effective layer version of the Significant Tornado Parameter (STP) to create the Violent Tornado Parameter (VTP).

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