Difference btw Sig-Tor fixed/effective?

[Melanie Kern-Favilla]

Can someone please tell me the difference between Significant-Tornado fixed layer and effective layer parameters? What is the minimum number that we would want to see for both Sig-Tor parameters?

THanks...

Melanie

 

[Josh Richardson]

The difference is simply what parameters are used in the formula:

Effective Layer: 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).

Fixed Layer: A multiple ingredient, composite index that includes 0-6 km bulk wind difference (6BWD), 0-1 km storm-relative helicity (SRH1), surface parcel CAPE (sbCAPE), surface parcel CIN (sbCIN), and surface parcel LCL height (sbLCL). This version of STP uses fixed layer calculations of vertical shear, and the surface lifted parcels, as an alternative to the "effective layer" version of STP.


When using the SPC's mesoanalysis these parameters include a description that goes into more detail.