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significant_tornado#

metpy.calc.significant_tornado(sbcape, surface_based_lcl_height, storm_helicity_1km, shear_6km)[source]#

Calculate the significant tornado parameter (fixed layer).

The significant tornado parameter is designed to identify environments favorable for the production of significant tornadoes contingent upon the development of supercells. It’s calculated according to the formula used on the SPC mesoanalysis page, updated in [Thompson2004]:

\[\text{SIGTOR} = \frac{\text{SBCAPE}}{1500 \text{J/kg}} * \frac{(2000 \text{m} - \text{LCL}_\text{SB})}{1000 \text{m}} * \frac{SRH_{\text{1km}}}{150 \text{m}^\text{s}/\text{s}^2} * \frac{\text{Shear}_\text{6km}}{20 \text{m/s}}\]

The lcl height is set to zero when the lcl is above 2000m and capped at 1 when below 1000m, and the shr6 term is set to 0 when shr6 is below 12.5 m/s and maxed out at 1.5 when shr6 exceeds 30 m/s.

Parameters:

  • sbcape (pint.Quantity) – Surface-based CAPE

  • surface_based_lcl_height (pint.Quantity) – Surface-based lifted condensation level

  • storm_helicity_1km (pint.Quantity) – Surface-1km storm-relative helicity

  • shear_6km (pint.Quantity) – Surface-6km bulk shear

Returns:

pint.Quantity – Significant tornado parameter

Examples

>>> from metpy.calc import significant_tornado
>>> from metpy.units import units
>>> significant_tornado(3000 * units('J/kg'), 750 * units.meters,
...                     150 * units('m^2/s^2'), 25 * units.knot).to_base_units()
<Quantity([1.28611111], 'dimensionless')>

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