By Urooj Raja
With the end of meteorological winter, severe weather season is upon us, raising the question of what the 2013 tornado season has in store for the U.S. One only needs to look to the past two tornado seasons to realize just how fickle Mother Nature can be from one year to the next.
After a record 2011 tornado season, which was the deadliest since 1953 and featured a whopping 1,690 tornadoes — the second-highest tornado count since 1953 — 2012 saw comparatively little tornado activity, with just 939 tornadoes. According to the National Oceanic and Atmospheric Administration, 2012 also saw a below-average fatality count.
Extreme Weather 101: Tornadoes
Large-scale weather patterns can have a major influence on severe weather outbreaks, and the intense drought that affected the heart of “Tornado Alley” in 2012 acted to squelch severe thunderstorms and tornadoes, since there was such little moisture and atmospheric instability available to produce tornado-forming storms. Tornado-prone states such as Oklahoma and Kansas were in severe to extreme drought conditions during the spring and summer of 2012, and in fact continue to be in drought conditions, according to the latest drought monitor released on March 7. It is quite possible that the lingering drought will affect tornado season in some of the Plains states again this year, unless significant drought relief occurs soon.
How does climate change impact tornado activity? Currently there is no scientific consensus on whether climate change has already altered tornado activity, or whether and how it will in the future. Because of warming air and ocean temperatures, there is already more water vapor available for thunderstorms to tap into, which may lead to more powerful thunderstorm updrafts. Research shows that global warming may increase atmospheric instability in parts of the U.S., increasing overall thunderstorm activity. However, a vital ingredient for tornado formation — wind shear — may actually decrease as the climate warms.
To the right is a preview of Climate Central’s Tornado Tracker, an interactive map displaying tornado activity from June 1, 2004 to date (updated hourly). As of March 13, there were 127 tornado reports this year. The total number of tornadoes during 2012 was 939, with April being the most active month, with 206 tornadoes. The 2012 tornado season caused 70 fatalities, and estimated property and crop losses of $1.6 billion, according to NOAA.
For additional information on tornadoes, you can watch our interview with NOAA tornado expert Harold Brooks, our report on tornado detection by Climate Central’s Heidi Cullen, and our extreme weather primer on tornadoes.
Climate Central's Andrew Freedman (@afreedma) contributed to this story.
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