Depending on who is asking, the answer to where is tornado alley varies greatly.
Who is asking? Why are they asking? Where are they asking from?
Much of the United States lives under a near constant yearly threat from tornadoes spawned from supercells.
The answer to where is tornado alley is actually quite complex.
Air Masses Collide
Traditionally, tornado alley is located across the middle of the country in the region known as the Great Plains.
The Great Plains are where most people think when they think of tornado alley — and for good reason.
Each Spring, air masses collide to form towering thunderstorms on the Great Plains. These thunderstorms produce hail, damaging winds, and tornadoes.
Tornadoes form when these varying air masses combine over the Great Plains. Hot and dry air moves over the Great Plains from the southwest. That air meets warm and moist air, carried northwards from the Gulf of Mexico. Overhead, cold air carried by the jet stream creates an atmosphere that is highly unstable. Where these masses of air meet is what is known as the dryline. Because of this, the dryline is located most predominantly each Spring on the Great Plains.
The dryline is responsible for the most violent and photogenic storms and tornadoes on Earth. Drylines are a favorite of storm chasers.
Traditional Tornado Alley
In reality, there is some truth to the old definition. The traditional alley lays across the middle of the country, from Canada to Mexico.
Tornadoes form most frequently in the spring months, from April to June. Typically, tornado season’s climax occurs in mid to late May each year.
However, tornado season’s do not always follow the same path. Some seasons explode violently with over 1000 tornadoes. Other seasons quietly sputter, with only a few hundred tornadoes over open lands.
Consequently, tornado alley’s location changes from year to year.
More importantly, tornado alley is not just the region known as the Great Plains.
Coining the Phrase
The term tornado alley was used first in 1952 by US Air Force meteorologists Major Ernest J. Fawbush and Captain Robert C. Miller. They used the term as part of a study of extreme weather events from Texas to Nebraska.
From there, tornado alley was also used in a headline in a New York Times article published May 26, 1957. The region known as tornado alley was defined as Texas, Oklahoma, Arkansas, Missouri, and Iowa in that article.
Expanding the Definition
We should expand the definition of tornado alley.
Tornado Alley is not located just on the Great Plains. Tornadoes frequently form across a larger portion of the country. This land area covers much of the United States.
Tornado Alley actually lays across a broad portion of the middle and eastern part of the country. In fact, tornado alley is located between the Rocky Mountains to the west, and the Appalachian mountains to the east.
In this region, tornadoes form at a pace unlike just about anywhere else on earth.
Recommended reading: Does that small hill or river protect you from tornadoes?
Strong to violent tornadoes form in this broad region more often than anywhere else in the country.
In fact, most strong to violent tornadoes form roughly along and east of Interstate 35 in the United States historically.
Scientists debate whether this represents a population density bias in tornado ratings. Scientific evidence indicates population density tends to increase tornado ratings because of more potential damage indicators being hit.
Scientists believe tornadoes are all capable of significant damage. Because of this, a tornado impacting any structure is a potentially deadly event.
Storm chasers decide to chase huge swaths of this region despite terrain challenges. Chasers successfully document tornadoes in this region each year. Because tornadoes are difficult to document here, chasers pursue tornadoes in this region with mixed success.
Storm chasers believe that there is another alley more interesting to them.
As a result, storm chasers pursue tornadoes in a region known as chase alley.
While tornadoes form more readily to the east, this region is not as chasable as the regions further west.
Photogenic storms form in the region to the west of interstate 35 far more often than regions east. Because of this, storm chasers call the region from West Texas up into the Northern High Plains chase alley.
This region combines several factors: good roads, flat terrain, and frequent storms to make a region where storm chasing is easier to accomplish.
Thus, storms forming over this region are oftentimes easy to spot and pursue. Oftentimes, chasers spot storms from dozens of miles away.
Because of this, storm chasers choose to chase in this region more often than others. Photographers capture stunning images each Spring. Scientists study storms in this region more often than others. Storm chasers pursue storms with greater success here.
However, storms forming here each spring is variable. Some storm seasons are busy years with hundreds of tornadoes in this region. Other years, chase alley goes quiet with only limited opportunities.
Its All in the Name
Your answer to where is tornado alley may just be more complicated than you thought.
Tornadoes form across much of the United States. The data says much of the country lives under this threat. Thus, be prepared for severe weather.
Your preparedness depends on your knowledge!
Here are some helpful links:
- Cars and Tornadoes: A Deadly Combination
- How big do tornadoes get?
- How do tornadoes form?
- Tornado Movement
Recently, scientists released a study. The results show greatest tornado frequency could be shifting east.