FALL TORNADO SEASON: Does It Really Exist (Great Plains)

FALL TORNADO SEASON: Does It Really Exist in the Great Plains.

Here is some research I did, please do not copy,

I use tornado days instead of actual number of tornadoes,
big outbreak days tend to skew the data.

Tornado days and 1970-2004 is more representative.

I did not include Texas, which has more tornado days.
I am breaking the down the state into regions, to get a better idea
for the tornado climatology of Texas.

North Dakota: Number of Tornado Days: 1970-2004
06 Tornado Days: September
02 Tornado Days: October
01 Tornado Days: November

South Dakota: Number of Tornado Days: 1970-2004
14 Tornado Days: September
06 Tornado Days: October
00 Tornado Days: November

Nebraska: Number of Tornado Days: 1970-2004
26 Tornado Days: September
18 Tornado Days: October
02 Tornado Days: November

Kansas: Number of Tornado Days: 1970-2004
31 Tornado Days: September
23 Tornado Days: October
08 Tornado Days: November

Oklahoma: Number of Tornado Days: 1970-2004
31 Tornado Days: August
43 Tornado Days: September
38 Tornado Days: October
27 Tornado Days: November

Texas: Working on.
71 Tornado Days: November

Texas Panhandle: Number of Tornado Days: 1970-2003
Panhandle consists of 44 counties in AMA and LUB CWA

15 Tornado Days: September
09 Tornado Days: October
04 Tornado Days: November

North Dakota: Average Tornado Days for Month: 1970-2004
0.17 Days: September
0.06 Days: October
0.03 Days: November

South Dakota: Average Tornado Days for Month: 1970-2004
0.40 Days: September
0.17 Days: October
0.00 Days: November

Nebraska: Average Tornado Days for Month: 1970-2004
0.74 Days: September
0.51 Days: October
0.06 Days: November

Kansas: Average Tornado Days for Month: 1970-2004
0.89 Days: September
0.66 Days: October
0.23 Days: November

Oklahoma: Average Tornado Days for Month: 1970-2004
1.23 Days: September
1.09 Days: October
0.77 Days: November

Texas: Working on
2.03 Days: November

Texas Panhandle:
Oklahoma: Average Tornado Days for Month: 1970-2003
Panhandle consists of 44 counties in AMA and LUB CWA

0.44 Days: September
0.26 Days: October
0.12 Days: November

114 tornadoes reported
3.26 Average Number of Tornadoes for Oklahoma

Tornado Outbreaks
27 tornadoes on 10-04-98
19 tornadoes on 10-09-01

These two days, skews the data.
In fact 10-4-98 and 10-09-01
-Makes up 40 percent of the total number of tornadoes in October 1970-2004

-37 percent of the total number of tornadoes in October 1950-2004

Only Oklahoma show a slight increase in tornado days
in September compare to the previous month of August.
31 tornado days in August, 43 tornado days in September.

Researched by: Mike Geukes
Copyright @ 2005 Mike Geukes (Please do not copy my research)

Yes it does exist. I would also have to say that it does depend where you are located.

Alabama Fall Tornadoes (1961-2000) for the Birmingham CWA:

31 Tornadoes: August
19 Tornadoes: September
07 Tornadoes: October
63 Tornadoes: November

This also carries over into the Winter, leaving one to wonder about a Winter Season.

Alabama Winter Tornadoes (1061-2000) for the Birmingham CWA

47 Tornadoes: December
50 Tornadoes: January
47 Tornadoes: February

So the question really depends on your perspective. Also, this does not include the Huntsville WSFO data.
I only concentrated on the Plains states, since most people
refer to the fall season, with Oklahoma. There are a few other
states, that do have a fall season.

Great work on doing Alabama, Chris.

Without looking at data, most of the recent October/November periods have seen events (that is, chase days for me and days with multiple tornado reports) in the Ohio Valley region (Indiana/Ohio), namely 10/24/01, 11/10/02, and 11/12/03.

After I 'expanded' my chase territory a few years ago, I started noticing that anything is possible year-round. I've seen lightning, thunder and hail within 100 miles of home every month of the year. There's no distinct pattern pointing to a specific time of year (other than obviously March-September), but it means that I always need to keep an eye on things even in the dead of winter.
I've done a little research on the fall season upper air patterns. I did this a few years ago spending a full day at the NWS office in Fort Worth looking at upper air charts for about 30 years.

What I found was a pretty persistent mean pattern very similar to this past May with a big upper cyclone entrenched over the eastern third of the CONUS. The result is successive surface cool fronts with very dry air plunging into the GOM resulting in very pleasant and dry conditions for the plains. You can also look at this in rainfall averages by month and at least around Texas and Oklahoma, October is an extremely dry month. At DFW, there have been several Octobers with not even a trace of rain recorded.

Even when a good system manages to come across in October, it is usually moisture starved with pretty low dewpoints.

The other problem we face is the the mid levels of the atmosphere have been warmed significantly from all of the spring and summertime convection. I first learned about this when Chuck Doswell talked about it in a presentation I attended. So, instability is usually pretty weak even when we get decent dewpoints because surface temps have cooled. A skew-t profile probably looks pretty pitiful.

However, the big plus we have is a super-charged GOM basin that is one big super-rich tropical airmass. So, the potential is always there for a significant event as far as fuel is concerned.

I'm also quite curious to know how many of the gulf coast states' tornado numbers quoted include those associated with tropical systems?
Thanks for providing those statistics! I sure hope something happens this fall; I'm suffering from major SDS at the moment with this cool weather we have here.
I think the fall season (especially November) is more of a southern thing, with Georgia, Alabama, Mississippi, and the like. If I remember right, Grazulis even mentions this in The Tornado . . . I'll have to read back through sometime and see if I can find where. I am almost always disappointed be the mythic fall season here in Oklahoma, though.

Every year I tell myself after spring is over that at least there's always fall. After seeing those stats for OK, I think I am ready to admit the truth: springtime only comes once a year here. It'll be a long wait. :(
Not really. It's just a small window of possibility, that only realizes itself once every 4-5 years. having said that, however, we're about due in OK.

Of course, we're about due in OK period.
In Ms it seems like every year around Thanksgiving we have a violent tornado or two. From mid November to Mid December it gets very active for those few weeks. It happens really fast, but it is also pretty significant. The only way I would consider driving a long distance to chase is if the target was in the Ms/Ar delta. The delta area which runs just north of Vicksburg up to Memphis and extends about 50 miles on each side of the Ms river is as flat as you will find with very few trees and lots of farm land. The road network is very good with many highways. It is really a great place to chase. Unfortunatly it is a small area and once you get out of it you hit big hills, tall trees and a poor road network. The fall season is just as good as the spring season (IMO) just much shorter. Here are a couple links to killer November tornadoes in the Jackson, Ms metro area. Both tornadoes hit between 5-6am.

The first, 2nd and 3rd link are tornadoes that all hit the same community in the last 13 years. The tornadoes discussed in the first and third link actually destroyed many of the same houses. I thought I would throw in the second and third tornado since they hit the same community eventhough they happened in the spring. The doppler radar site for Jackson is actually less than a half mile south of the tornado's path. The third and fourth link is to a tornado that hit Madison, Ms on 11/24/01. The damage in the photos on the fourth link were to new homes that were very well built in an upper class neighborhood. Tornadoes actually do hit more than just trailer parks in the south, lol.
I'll refer everyone to Harold Brook's climo research on the NSSL page. Here's the link to the 1970-1999 Tornado Probability animation: http://www.nssl.noaa.gov/hazard/tanim/torw8099.html .

As you can see, there is an increase in tornado probability during the fall months, starting in the southern plains in September and early October, and moving eastward into the southeastern US during October and November.

As someone else noted (Dan R I think), there have been classic, east-of-the-Mississippi-River outbreaks during the falls months. There outbreaks are usually very synoptically-evident and relatively easy to forecast several days in advance (smaller details not withstanding).