I’ve been having a discussion with my chase partner about El Nino and La Nina and whether or not these cycles produce tornado outbreaks. While this is turning out to be far more complex than just a simple question.
However I have forced myself into looking at this further and what I have found is no reason to expect more or fewer tornadoes overall. But the findings show clear evidence of geographical shifts in tornado activity within the United States when comparing strong El Nino years to La Nina years.
Comparing tornado activity during El Nino and La Nina events by calculating a ratio of tornadoes on a state-by-state basis. Findings show more tornadoes in the central and southern plains and the Gulf Coast during strong El Nino years, with a shift to more tornadoes in the lower Midwest, the Ohio and Tennessee valleys, and the mid-Atlantic region during La Nina years. This study also showed there is little evidence that El Ninos are associated with more or less tornado activity.
La Nina events, however, seem to favor an above-average annual number of tornadoes in select geographical regions. The strengths of these cycles also seem to be a factor in this data as well.
Another key finding is that tornadoes during a La Nina are stronger and remain on the ground longer than those observed during an El Nino. That means an increased danger of large destructive and deadly tornadoes during the cold phase. There is also an increased risk of “tornado swarms” or outbreaks of 40 or more twisters from a single weather system in a La Nina season. Some researchers believe a recent climate shift favoring a cooler Pacific and more frequent La Nina events suggests we have entered a period of increasing severe storms that could last a decade or more.
Current ENSO Oct-Nov models show severe weakening or the end or of the El Nino cycle in May. Then moving into a neutral cycle. Neutral cycles tend to produce less tornados then during the El Nino and La Nina cycles. So maybe 2010 turns out to be a bigger bust than 2009.
Again I’m focusing on El Nino and La Nina and there are way too many factors to base whether or not tornado outbreaks will or will not happen. Could there and will there be some other weather phenomona that will break the norm and increase our chances. Other chasers have predicted a 2010 outbrake as did myself, but is that just may be more wishcasting that actual scientific prediction.