What the heck is STP??? It is Significant tornado parameter which is a measurement of 5 specific meteorological things. Here is the definition form the SPC:
“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), and surface parcel LCL height (sbLCL). This version of STP mimics the original formulation presented by Thompson et al. (2003) by using fixed-layer calculations of vertical shear, and substitutes the surface lifted parcels as an alternative to the ML parcels in the “effective layer” version of STP.”
Basically it rates the atmosphere’s ability to produce a tornado on a scale of 1-10. In cases where there are large violent tornadoes the STP is usually around a 7-9. In the case of a 3, which is what it is looking like for N Georgia, that means that there is a pretty good chance that we could see a tornado across parts of the area tonight. Here is the latest STP for 4amand yes you will notice that a majority of the area in in a 2-3 category which definitely concerns me. We will have the instability in place and also quite a bit of helicity so as
line moves in there is either the chance of some of the cells along the line could spin up, or we could see a few individual cells form and rotate. This is a changing situation but I will keep you posted throughout the night.
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On a scale of 1-10 I am going with a 4 on this one for the threat for damaging winds and a very slim chance of a brief spinup.
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