Severe storms moved through the Tennessee Valley on Thursday, Jan. 12 producing an EF 1 tornado that tracked through Moulton and Decatur. There were also numerous reports of damaging winds. You might remember New Year’s Day of 2022 when a couple of tornadoes were confirmed. While tornadoes can happen any time of the year in North Alabama, you might think January isn’t a month known for tornadoes. However, that’s not the case.
In order for tornadoes to form, you need thunderstorms that thrive off of warm, humid air and a lifting source. The source is a low-pressure system. As the low-pressure system approaches, warm, humid air is ushered into our area by southerly winds ahead of it. This is all happening at the surface of our atmosphere. This warm, humid air mass is more common across the Deep South during the winter months vs. the Northeast, which typically sees many more cold-air intrusions.
Tornadoes form when there’s enough wind shear in the atmosphere which is enhanced by a strong jet stream. The jet stream is typically strongest in the winter due to the strong boundary between cold and warm air. Wind shear is the change in wind direction and speed with height. Winds blowing from the south, southeast at the surface to more westerly aloft favors development of tornadoes. Also, winds increasing in speed with height favors development. In the Tennessee Valley, it’s common to have periods of warmer weather in the winter. It’s the combination between the strong, active jet stream and warmer, humid air that leads to tornado occurrence in January.
Alabama has seen 149 tornadoes in January with records dating back to 1950. January is the 7th-most active month for tornadoes of the year for the state.
Looking at the Tennessee Valley, January has seen 17 tornadoes in a period from 1950 to 2019. If the right ingredients are there, tornadoes can occur any time of the year, even in winter.