This week, parts of the Deep South faced a severe weather outbreak that brought one deadly tornado to a Birmingham, Alabama suburb. Which brings up the question: is this normal?
Wintertime weather in the U.S. is usually dominated by blizzards and ice storms that can incapacitate parts of the country. However, while tornadoes are rare this time of year, they do happen and can be just as violent as they are in the spring.
First, it’s important to remember tornadoes have been reported in every state across the continental United States with a yearly average of around 1,000. The United States is a very large in size, so while every state has reported a tornado, some states receive more than others and at different times of the year.
Back to the wintertime tornadoes — this time of year, storm systems that bring snow and ice to the northern states can also bring severe weather outbreaks to the southern states. It’s within these storm systems where tornadoes are possible.
Ingredients for large, violent tornadoes (EF3 to EF5) is quite long. Even under perfect conditions, strong tornadoes are very rare. On the contrary, weak tornadoes (EF0 to EF2) are most common and can spin up briefly under less than perfect conditions.
The frequency and strength of tornadoes in the winter is highly dependent on the clashing of warm, moist air with cold, dry air. Since there’s usually more cold, dry air than warm, moist air, the tornadoes are typically weaker and short lived compared to the long track and violent ones in the spring.
Based on data collected from the National Weather Service from 1982 to 2011, the most probable areas to see tornadoes are in the southern states as shown in the image above. This map is based on the frequency of seeing a tornado, not its strength.
The probability of tornadoes increases significantly and also shifts more to the Great Plains in late May which is the peak of tornado season.
The KXAN First Warning Weather team highly suggests everyone to buy a NOAA Weather Radio to inform and wake you of overnight severe weather. And of course, keep it tuned into KXAN when severe weather strikes.