* The Gulf of Mexico is a warm body of water that provides ample moisture for thunderstorms.

* When cold fronts from the north interact with this warm, moist air, it can create the perfect conditions for tornadoes to form.

Frequent cold fronts in December

* The winter months are when cold fronts are most common in the United States.

* These fronts can bring strong winds and cold temperatures, which can help to create the right conditions for tornadoes.

Topography

* The terrain in the southern United States can also contribute to the formation of tornadoes. The Appalachian Mountains can help to focus and intensify cold fronts, which can lead to increased tornado activity.

Climate change

* Some scientists believe that climate change could be making tornadoes more frequent and severe in the southern United States.

* As the climate warms, the Gulf of Mexico is also becoming warmer, which can provide more moisture for thunderstorms.

* Additionally, climate change could be leading to changes in the jet stream, which can affect the frequency and severity of cold fronts.

All of these factors combine to make the southern United States more prone to December tornadoes.