A study was done to find out if a warm El Niño weather pattern or a cold La Niña weather pattern could potentially affect the numbers, locations, and strengths of tornadoes in the United States. As far as the number of tornadoes, there was little difference. However, significant differences were found regarding violent tornadoes and outbreaks.
It was found that La Niña years produce:
- Longer-than-average tornado tracks
- More violent tornadoes
- A better probability of a tornado outbreak
El Niño years produce:
- Shorter-than-average tornado tracks
- Less violent tornadoes
- Only a slim possibility of a tornado outbreak
Read more at the link below.
What are El Niño and La Niña?
Note: El Niño and La Niña seasons run from one year into the next, similar to a school year that runs from, say, August 2014 through May 2015.
Strong and moderate years:
- La Niña: 2010–2011, 2007–2008, 1999–2000, 1998–1999
- El Niño: 2009–2010, 2002–2003, 1997–1998