This is why December is one of the peak months for tornado activity in the southern US.

Here's a detailed explanation of the meteorological factors that contribute to December tornadoes in the southern US:

1. Warm, moist air from the Gulf of Mexico: The Gulf of Mexico is a warm body of water that acts as a reservoir of warm, moist air. This air is transported northward by prevailing southerly winds and overspreads the southern US. The warm, moist air provides the necessary moisture and instability for thunderstorm development.

2. Cold fronts: During the winter months, cold fronts associated with mid-latitude cyclones frequently move through the southern US. As a cold front approaches, it collides with the warm, moist air from the Gulf of Mexico. This collision creates a zone of atmospheric instability, which can trigger thunderstorms.

3. Jet stream: The jet stream is a fast-moving air current located in the upper atmosphere. During the winter, the jet stream is typically positioned over the southern US. The jet stream provides the upper-level winds that can organize thunderstorms into supercell structures, which are more likely to produce tornadoes.

4. Lifting mechanisms: In addition to the warm, moist air and cold fronts, certain lifting mechanisms are necessary to initiate thunderstorm updrafts. These lifting mechanisms include terrain features, such as hills and mountains, and dry lines. A dry line is a boundary between dry air and moist air. When the dry line intersects with a cold front, it can provide additional lift for thunderstorms.

The combination of these meteorological factors creates the ideal conditions for severe thunderstorms, including tornadoes, in the southern US during December. While tornadoes can occur in any month of the year in the southern US, they are most common during the spring (April-May) and fall (October-November) months.