‘Tornado Alley’ and other things to know during tornado season

Science and Innovation

Severe thunderstorms ravaged across the southeast earlier this week, resulting in at least one confirmed tornado at Jacksonville State University in Alabama.

Now, parts of Florida and coastal communities in Georgia and the Carolinas are at risk for severe weather, which may include tornadoes.

Read on for a look at why tornadoes occur and what to do if you’re caught in one.

What is a tornado?

Essentially, a tornado is a column of air that spins at a high speed.

The column typically forms from a thunderstorm, stretching down and eventually reaching the ground below. When this happens, the column takes the shape of a funnel — also known as a funnel cloud, according to the Ready Campaign, a national public service campaign that helps Americans respond to natural and man-made disasters, among other things.

When do tornadoes typically occur?

“Peak tornado” season hits the South in March and ends around May, the Virginia Department of Transportation says on its website. The severe weather pattern usually makes its way north, with the majority of tornadoes hitting northern states over the summer.

“Half of tornadoes typically happen in May and June,” Harold Brooks, senior research scientist at the National Oceanic and Atmospheric Administration’s (NOAA) Severe Storms Laboratory, told AccuWeather in April 2017.

However, tornadoes tend to hit the Gulf coast earlier during the spring, NOAA explains on its website.

“But, remember, tornadoes can happen at any time of year. Tornadoes can also happen at any time of day or night, but most tornadoes occur between 4 to 9 p.m.,” NOAA adds.

Why do tornadoes occur and how do they form?

Most tornadoes form from supercells, also known as a rotating thunderstorm or a mesocyclone.

A supercell is typically a thunderstorm with the “winds already in motion,” according to National Geographic. It requires a combination of warm, moist air and cold, dry air — which are the “ingredients for a regular thunderstorm,” Brooks told the publication.

To put it simply, warm, moist air near the earth’s surface begins to rise, blowing in one direction at one speed. Subsequently, the cold air above is blowing in a different direction at a different speed. This creates a wind shear, which causes the air to rotate in a column. From here, if the air column gets caught in the updraft of a supercell, it causes the air to spin faster and create a funnel shape. The funnel of air becomes a tornado as it extends toward the earth and reaches the ground below.

It’s worth noting, however, that supercells are relatively rare. According to the National Weather Service (NWS), supercells are the least common type of thunderstorm.” Roughly one in a thousand storms become supercells. From there, only one in about six of those supercells will become a tornado, National Geographic reports.

But if they do form, “they have a high propensity to produce severe weather, including damaging winds, very large hail, and sometimes weak to violent tornadoes,” according to the NWS.

Where do tornadoes typically hit?

While tornadoes can form almost anywhere given the right conditions, they commonly touch down in Florida and an area of the U.S. called “tornado alley.”

Tornado alley, according to the National Centers for Environmental Information (NCEI), is a “nickname given to an area in the southern plains of the central United States that consistently experiences a high frequency of tornadoes each year.”

Tornado alley includes parts of central Texas, then moving into Great Plains states such as Oklahoma, Kansas, Nebraska, North Dakota and South Dakota. Parts of Iowa, Missouri and eastern Colorado are also considered part of tornado alley.

What can you do to protect yourself during a tornado?

The intensity of a tornado is measured using the Fujita scale, which ranges from an F0 to an F5. The latter is the most destructive and dangerous type of tornado. The winds from an F5 tornado can reach over 200 miles an hour.

To protect yourself from a tornado, it’s important to know the difference between a tornado watch and a tornado warning: a watch indicates a tornado could form, while a warning means a tornado has already been spotted, according to the Ready Campaign.

Some homes in Tornado-alley are equipped with Federal Emergency Management Agency (FEMA)-approved “safe rooms,” which, according to the organization, is a “hardened structure specifically designed to meet FEMA criteria and provide life-safety protection in extreme wind events, including tornadoes and hurricanes.”

However, if you are not able to reach a safe room during a tornado, it’s best to go to the lowest level of a structure, such as a basement. It is important to stay away from all windows, doors or anything else that leads outside, the Ready Campaign recommends. Wearing a helmet and placing blankets, pillows or even a mattress over your body may protect you from debris if a tornado hits your home or a nearby building.

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