The tornadoes that touched down from a winter storm near Blakely and Colquitt (southwest of Albany) on December 17 last year were unusual. Even more out of the ordinary was the new outbreak of January 10-11 this year. Georgia was spared the worst this time. But Pickens Co., Alabama (near Tuscaloosa) reported three tornado-related fatalities.
Events like these were all produced by single winter storm systems. Those aren’t unusual by themselves. A typical winter storm consists of a cold front, a warm front and a low pressure center. It begins with a mass of cold air moving from the northwestern end of the continent towards the southeast. At the same time, mild air flows into Texas, Louisiana, Mississippi, Alabama and the Florida Panhandle from the Gulf of Mexico. These two airmasses now collide, as they don’t mix well. A sharp line, visible on the radar the evening of January 10, marks the edge of the colder air. It scoops up incoming warm Gulf air like a huge bulldozer. Farther northeast, the warm air is producing a warm front. It comes with steady showers that are just an overture for the main storm system that follows. Where the warm front and cold front meet, the winds are forming the typical counterclockwise pattern of low-pressure cells, and there is the center of this so-called cold-core storm.
The unusual part this month, and last December, was that its cold core was warmer than normal. Air rising rapidly from the ground allowed for enormous amounts of moisture to flow into the system. Moisture is water vapor, and to a storm that’s energy, like gasoline to an engine. Ultimately, the reason why we’ve been seeing tornadoes during the cold season, instead of the usual April-May period, is the increased water temperature in the Gulf of Mexico.
Understanding these mechanisms doesn’t help if your mobile home is flung 200 feet through the air, like the tragic case in Bossier Parish, Louisiana on January 11. The events emphasize that even more efforts are required for storm safety. Mobile homes need to be anchored securely to the ground. Large trees that can get uprooted by a storm, drop on a house and hurt its residents, need to be inspected and possibly removed. Promoting more measures to increase safety in severe storms would be a nifty job for county governments.