Tornado Alley in the context of Missouri

The Gulf of Mexico (Spanish: Golfo de México) is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southwest and south by the Mexican states of Tamaulipas, Veracruz, Tabasco, Campeche, Yucatán, and Quintana Roo; and on the southeast by Cuba.

The Gulf of Mexico basin is roughly oval and is about 810 nautical miles (1,500 kilometres; 930 miles) wide. Its floor consists of sedimentary rocks and recent sediments. It is connected to part of the Atlantic Ocean through the Straits of Florida between the U.S. and Cuba, and with the Caribbean Sea via the Yucatán Channel between Mexico and Cuba. Because of its narrow connection to the Atlantic Ocean, the gulf has very small tidal ranges.Moisture from the Gulf of Mexico also contributes to weather across the United States, including severe weather in Tornado Alley.

A supercell is a thunderstorm characterized by the presence of a mesocyclone, a deep, persistently rotating updraft. Due to this, these storms are sometimes referred to as rotating thunderstorms. Of the four main classifications of thunderstorms—supercell, squall line, multi-cell, and single-cell—supercells are the least common overall and have the potential to be the most severe. Supercells are often isolated from other thunderstorms, and can dominate the local weather up to 32 kilometres (20 mi) away. They tend to last 2–4 hours, but under highly favorable conditions, can last even longer.

Supercells are often put into three classification types: "classic" (normal precipitation level), low-precipitation (LP), and high-precipitation (HP). Low-precipitation supercells are usually found in climates that are more arid, such as the high plains of the United States, and high-precipitation supercells are most often found in moist climates. Supercells can occur anywhere in the world under the right pre-existing weather conditions, but they are most common in the Great Plains of the United States in an area known as Tornado Alley. A high number of supercells are seen in many parts of Europe as well as in the Tornado Corridor of Argentina, Uruguay, southern Brazil, and Paraguay.

A tornado outbreak is the occurrence of multiple tornadoes spawned by the same synoptic scale weather system. The number of tornadoes required to qualify as an outbreak typically are at least six to ten, with at least two rotational locations (if squall line) or at least two supercells producing multiple tornadoes.

The tornadoes usually occur within the same day or continue into the early morning hours of the succeeding day, and within the same region. Most definitions allow for a break in tornado activity (time elapsed from the end of the last tornado to the beginning of the next tornado) of six hours. If tornado activity indeed resumes after such a lull, many definitions consider the event to be a new outbreak. A series of continuous or nearly continuous tornado outbreak days is a tornado outbreak sequence. In the United States and Canada, tornado outbreaks usually occur from March through June in the Great Plains, the Midwestern United States, and the Southeastern United States in an area colloquially referred to as Tornado Alley. A secondary less active and annually inconsistent tornado "season" in the U.S. occurs in late autumn. Tornado outbreaks can also occur during other times of the year and in other parts of the world. In Europe, tornado season typically peaks around the summer months, although windstorms can spawn tornadoes in other seasons as well.

Tornadogenesis is the process by which a tornado forms. There are many types of tornadoes, varying in methods of formation. Despite ongoing scientific study and high-profile research projects such as VORTEX, tornadogenesis remains a complex process, and the intricacies of many tornado formation mechanisms are still poorly understood.

A tornado is a violently rotating column of air in contact with the surface and a cumuliform cloud base. Tornado formation is caused by the stretching and aggregating/merging of environmental and/or storm-induced vorticity that tightens into an intense vortex. There are various ways this may come about and thus various forms and sub-forms of tornadoes. Although each tornado is unique, most kinds of tornadoes go through a life cycle of formation, maturation, and dissipation. The process by which a tornado dissipates or decays, occasionally conjured as tornadolysis, is of particular interest for study as is tornadogenesis, longevity, and intensity.