Tornadoes and lcl's

[Mark Sefried]

Was wondering what most chasers would say would be the highest lcl's you would want to see in a supercell that could produce a tornado. Landspouts don't count though because of course as they can be fairly high based. What was the highest lcl you have ever seen in a supercell that produced a tornado in meters?

 

[afischer]

What was the highest lcl you have ever seen in a supercell that produced a tornado in meters?

Great question.

The Onida, SD tornado of August 24, 2006 (the first of 10 tors from that storm) occurred in an environment with surface T/Td of 90F/69F and MLLCL around 1600m (possibly even higher, but this is my best estimate using a modified sounding; it was right at the nose of the hot prod and there wasn't a METAR immediately adjacent the storm). This is the highest I've witnessed.

Manchester, KS on April 6, 2006 was pretty moisture starved, too... 1500m MLLCL at best on that one.

I didn't see the Beatrice tornado on April 15, 2006 but if memory serves the MLLCLs were horrendous... like 77F/55F at the surface? Yikes!

Guess this is an interesting example of how you can have tornadoes with borderline terrible MLLCLs given other favorable parameters (e.g. large low-level cape; extreme 1km SRH)... and in contrast, can have no tornadic storms with favorable MLLCLs but lack of significant large scale ascent/mesoscale focus.

 

[Dustin Wilcox]

Manchester, KS on April 6, 2006 was pretty moisture starved, too... 1500m MLLCL at best on that one.

I didn't see the Beatrice tornado on April 15, 2006 but if memory serves the MLLCLs were horrendous... like 77F/55F at the surface? Yikes!

While I cant remember the numbers I do remember visually that the April 6th Hanover tornado was extremly high based, however while I dont recall the LCL numbers the Beatrice tornado did not seem all that high based, wasnt a gopher killer but I'm not sure you could term it high based.

Beatrice Base

See avatar for april 6th high based storm

 

[Mikey Gribble]

I am pretty sure we got into the upper 50's on the Beatrice tornado. I am shooting from memory though so I could be wrong. You could check the severe thunderstorm events page and find out. I would do it right now, but I'm on my girlfriend's computer and she doesn't have java (you have to loop the surface chart to view it).
Anyways, I think t-td of about 20 like everybody else said is about the limit. If you are going to have a bigger spread than that, I usually won't chase unless it's close to home.

 

[Mikey Gribble]

Btw I just thought I should mention there are more to the LCL than just the dewpoint spread. I think 20 degrees is a pretty good rule of thumb though.

 

[afischer]

I am pretty sure we got into the upper 50's on the Beatrice tornado.

You're right; BIE jumped from 77/55 at 3pm to 77/57 at 4pm.

 

[Van DeWald]

Here's the SPC LCL Mesoanalysis data from the 4/16/2006 BIE tornado.

 

[afischer]

Here's the SPC LCL Mesoanalysis data from the 4/16/2006 BIE tornado.

Nice... that suggests ML LCL heights of 1700m associated with that tornadic storm (appears reasonable given the environment). That is definitely the highest I've seen on the mesoanalysis page in association with a strong, long-track tornado!