When severe weather strikes the United States, it’s important for people across the country to be prepared for potential hail, rain, damaging winds, and more.
Tornadoes can cause power outages for thousands of people, result in catastrophic property damage, and even lead to fatalities. The U.S. experiences approximately 1,200 tornadoes each year.
Experts emphasize the significance of monitoring forecasts and understanding the different stages of weather warnings to ensure safety.
Here’s what you need to know about the causes of these storms and the alerts for watches, warnings, and emergencies.
What Can Trigger a Tornado?
Large areas of low atmospheric pressure associated with certain storm systems can give rise to tornadoes. Low pressure is linked to stormy weather, and the lower the pressure, the more intense the storm can be. Low-pressure systems draw air into them, resulting in rain and winds.
“In the spring and transition seasons—spring, fall, and even winter—we experience these very strong extratropical low-pressure systems,” explained Victor Gensini, a professor of atmospheric sciences at Northern Illinois University. “These are storm systems that occur in the mid-latitudes of each hemisphere.”
“If you imagine a map of the United States and draw a large U shape across it, that would represent a significant trough,” he added. “This trough helps facilitate the formation of a low-pressure area and a powerful storm system.”
How Do Storm Systems Develop into Tornadoes?
These storm systems generate extremely strong winds and hail.
When combined with warm and humid air on one side of the low-pressure storm system that wants to rise, thunderstorms can occur.
Under the right conditions—warm, moist air near the ground, cooler, dry air aloft, and changes in wind direction—these storms can escalate into tornadoes, as per the National Weather Service.
“In an atmosphere where it’s warm at lower levels and cold aloft, and there’s also humidity at lower levels, air can rise rapidly through thunderstorm updrafts, leading to potentially severe weather,” stated Paul Markowski, a meteorology professor at Penn State University. “Typically, the stronger the thunderstorm updraft—the term for where the air is rising—the greater the potential for damaging winds, hail, and possibly tornadoes.
“Another component you need along with the temperature variation with altitude is wind shear, which refers to how much the winds change from the lower atmosphere to the upper atmosphere,” he added.
What Are the Differences Between a Tornado Watch, Warning, and Emergency?
The Storm Prediction Center of the National Weather Service issues a tornado watch for an area, up to 10 hours in advance of a storm, when conditions indicate a potential for tornadoes. Individuals in that area, which typically spans several counties or states, should be prepared for a possible warning.
A warning is issued by local forecast offices when weather radar suggests an approaching tornado or when one has already been spotted. This usually covers a smaller region such as a city or county. People in the area need to take immediate action, such as seeking shelter on the lowest floor of a building and avoiding windows.
Tornado emergencies are the highest alert level issued by the weather service and are declared when a tornado has touched down in an area, resulting in confirmed catastrophic damage. While rare, these situations require immediate sheltering in place.
What’s the Best Way to Prepare?
Experts recommend having multiple ways to receive watches and warnings and understanding the significance of each. Weather radios can be particularly useful if power is lost and regular TVs and radios are no longer operational.
It’s crucial to have secure, enclosed, and underground shelters—or rooms above ground designed to withstand tornado-level winds—prepared in advance.
“In many parts of the country prone to tornadoes, there may not be underground options available,” Markowski noted. “Leaving your house may not necessarily be safer. Therefore, if you are indoors, put as many walls between you and the tornado as possible. Move away from windows and seek refuge in an interior room like a bathroom.”
By Alexa St. John
