STP clipping in areas with CIN/MLCIN

[Dan Robinson]

I've noticed that many model charts clip the effective STP plots to zero where convective inhibition (CIN or MLCIN) is above a certain threshold, implying storms can't survive there and cannot utilize any of that favorable environment. However, I've observed many events where tornadic storms occurred within these clipped zones. Since established supercells are able to overcome some CIN, would it make more sense to just plot effective STP as-is?

 

[Luke Penney]

Or maybe display that STP but put shading over the higher-CIN areas, like a number of sources do for other parameters:

 

[JamesCaruso]

I always thought STP charts were intended to show the parameters verbatim, without regard to whether storms could form or be sustained? Even without CIN, storm formation could be conditional due to lack of forcing. I think it’s better to show STP verbatim, without factoring in any other variables that affect storm formation, unless you’re going to factor in *all* other variables that could affect storm formation.

 

[Lou Ruh]

According to the SPC mesoanalysis page, STP is

STP = (sbCAPE/1500 J kg-1) * ((2000-sbLCL)/1000 m) * (SRH1/150 m2 s-2) * (6BWD/20 m s-1)* ((200+sbCIN)/150 J kg-1)

The sbLCL term is set to 1.0 when sbLCL < 1000 m, and set to 0.0 when sbLCL > 2000 m; the sbCIN term is set to 1.0 when sbCIN > -50 J kg-1, and set to 0.0 when sbCIN < -200; the 6BWD term is capped at a value of 1.5 for 6BWD > 30 m s-1, and set to 0.0 when 6BWD < 12.5 m s-1.

So, assuming I am not missing something, the index is zero if sbCIN is less than -200.