Comments on: What about those tornadoes?

By: Greg Laden

Greg Laden — Sat, 07 Dec 2013 03:03:30 +0000

Actually ,what is going on here is that for some reason the right hand side of the graphic is cut off. Click on it and see the last year.

By: Harold Brooks

Harold Brooks — Sat, 07 Dec 2013 02:53:42 +0000

Starts in 1990, 22nd year is 2011. 2011 is a huge area year (the last two weeks of April). The only comparable year in the database is 1974. 2008 (Super Tuesday and a few days in May) is the 2nd one on this graph. ’98 (x-axis=9) was the biggest area of the 1998. Large area years tend to be dominated by the big outbreaks. 2012 is much lower than 2008 or d2008, below the 2010 number. I couldn’t quite draw this chart freehand without looking at the data, but I could get most of the details.

By: Greg Laden

Greg Laden — Fri, 06 Dec 2013 15:57:47 +0000

This was put together roughly. It is years since 1990 so it goes to 2012. This was originally made to display differences oner a few decades to test a specific question in a different post about or peoples recollection of changes in tornado frequency and severity.

It would be nice to distill this diwn to energy levels.

By: Harold Brooks

Harold Brooks — Fri, 06 Dec 2013 15:31:31 +0000

The final graph only goes to 2011. There’s really no reason not to include data for area further back in time. F0 tornadoes contribute a few % to the F1+ tornado areas. For example, in 2011, the F0s only cover ~75 sq. miles out of the >2800 total. Looking at F1+ is relatively consistent for many purposes, but the F0 area is small enough, it doesn’t matter a lot. It’s not clear what impact the change in width definition from mean to max in ’95 had on the data, but more attention to damage surveys for major tornadoes can add to both the width and length estimates.
I was having a conversation with a forecaster a couple of days ago about the derecho definition problem. We use an outcome-based definition, rather than a physical process definition, so that it’s more susceptible to report changes.

By: Greg Laden

Greg Laden — Fri, 06 Dec 2013 03:15:22 +0000

Yes, there’ s a definition: damage across more than 240 miles, wind gusts of 58 mph+ along most of the length of the storm, distinct 75 mph+ gusts frequently, straight line (not tornadic) winds.

The storm prediction center has a database of storms that can be mined for derecho events:

http://www.spc.noaa.gov/climo/online/sp3/plot.php

and there is a derecho database here:

http://www.nssl.noaa.gov/users/mcon/public_html/derlist.htm

I’ve not worked with any of these data myself.

By: Lawrence

Lawrence — Thu, 05 Dec 2013 19:58:44 +0000

Along the lines of the last paragraph –

Is there a scientifically accepted definition of ‘derecho’ and a database of them? It would be interesting to track frequency and size of these big straight line storms along with tornados, making it easier to see how shear plays out.

The historical data is probably even more sparse than what we have for tornados, but it would be interesting to see going forward.

By: Greg Laden

Greg Laden — Thu, 05 Dec 2013 19:12:37 +0000

Ugh. Thanks Beth. I’ll try to do that when I am at an appropriate computer in a about two days from now.

For now, let us arbitrarily assign for the purposes of this post only the meant “Greater than” to the symbol “<"

By: Beth

Beth — Thu, 05 Dec 2013 15:38:41 +0000

You need to reverse the inequality sign in your graph. It should be > 1 not < 1.