STP Importance

[Jon Miller]

Another question - How important are the two Significant Tornado Parameters (STP) , given in forecast models, in planning a chase stratedgy ? Do they mean a lot or just of casual interest ? Thanks

Jon Miller
KT8NDO

 

[Dustin Wilcox]

Personally I don't pay much attention to them in planning a chase, I try to look at all the factors individually while in the planning stage, I try to reserve even looking at the composite indicies until crunch time, often just using them to just get a quick idea of where the greatest parameters are poking. Even then I still don't value the STP compostie very much or even most other composites for that matter, I have seen tornadoes in areas with STP values @ 1 and I have also seen isolated sups form in an area with an STP of 8 only to not produce squat, often the composites can be thrown off when one of the factors in the equation is through the roof, while another is far from favorable, example you might get LCL's of 2000 with sbCAPE of 8000j/kg which would still probably register a decent value on the STP, despite the fact that LCL's are to high to be favorable for tornadoes, obviously if the values are super high its likely all the factors in the equation are favorable, but even then there are factors not included in the equation that might not be favorable. Here is the equation [FONT=Arial, Helvetica, sans-serif][FONT=Arial, Helvetica, sans-serif]STP = (sbCAPE/1500 J kg^-1) * ((2000-sbLCL)/1500 m) * (SRH1/100 m² s^-2) * (6BWD/20 m s^-1) * ((200+sbCIN)/150 J kg^-1)
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[rdale]

HIGHLY suggest you take a look at Doswell and Shultz's paper on using indices...

http://www.ejssm.org/ojs/index.php/ejssm/article/view/11/0

 

[Shane Adams]

I look at them when I'm with someone who has a laptop and I'm bored. They're fun, but unnecessary. Most of those custom label parameter formulas more or less point to the same areas a basic surface analysis would lead you. All you need is surface and lowest 1km data for pinpointing the ripest areas for tornadoes, once it's obvious what overall region supercells will be in.

At least that's how I do it.