Many people don’t realize that in the southern half of the country that we actually have two ‘tornado seasons’ each year.  Most tornadoes in our part of the country occur in the spring months of March, April, and May.  But we do have a second typically small tornado season from October into December.  

This December has brought some very unusual weather to the ArkLaTex.  As of this writing, this December ranks as the second warmest on record since 1875 and I don’t really see much in our extended forecast for the rest of the month that will change this much.  The bigger weather news has been the recent rash of tornado outbreaks that have occurred across the country.  We have witnessed two decent storm systems produce numerous tornadoes in less than a week.  The obvious questions that come to mind are why? and could there be more? 

In my last blog entry, I provided some insight on the weather that we could experience this winter.  I pointed out the water temperatures over much of the Pacific are below normal.  In fact, the PDO index has recently been the lowest since 2011.  I remember 2011 very well.  It was the year of the drought in the ArkLaTex that produced over sixty days of 100-degree heat.  The spring of 2011 was also a very active tornado season that is the deadliest on record and produced the 3rd most tornadoes.

After last week’s significant tornado outbreak in the Midwest, I got to thinking.  Could the cold waters of the Pacific lead to an increase in the frequency of significant tornado outbreaks?  I found a very interesting list of the top ten tornado outbreaks not just based on tornado numbers or deaths but based on the size and duration of the tornadoes they produced.  If you include the December 10, 2021 outbreak I had 11 outbreaks to consider.

It turns out that TEN out of the eleven outbreaks occurred when the PDO was below normal.  The last report on the PDO in November showed it to be at -2.71.  In October the PDO came in at a whopping -3.15.  The last time that the PDO was that negative was back in 2011!  THREE of the top ten outbreaks occurred in 2011!  So it’s pretty clear that there is some sort of correlation between Pacific water temperatures and the chance of seeing decent tornado outbreaks.  This could partially explain why we have seen so many tornadoes this month. It may also offer a warning to what COULD happen this coming spring.  It appears that the Pacific is starting to warm up again.  Let’s hope that continues.  Stay tuned! 

Todd Warren