Severe weather events in the United States can bring destructive forces like hail, torrential rain, and intense winds, leaving destruction in their wake. Tornadoes are one of the most feared natural disasters in the country, leading to widespread power outages, significant property damage, and even loss of life. On average, the U.S. experiences about 1,200 tornadoes annually. Understanding weather forecasts and the terminology for different tornado alerts is crucial for staying safe during these events.
Tornadoes typically form in regions of low atmospheric pressure that accompany certain storm systems. These low-pressure systems are synonymous with stormy weather and, the lower the pressure, the more intense a storm can become. The system draws air inwards, resulting in strong winds and precipitation. According to Victor Gensini, an atmospheric science professor at Northern Illinois University, these intense storm systems, known as extratropical low-pressure systems, are common during transitional seasons like spring and fall. They occur predominantly in the mid-latitudes.
Gensini explains that a U-shaped contour across the United States map symbolizes a significant trough that fosters the development of these powerful storm systems. The interaction of warm, moist air at the surface with cooler, dryer air aloft is conducive to thunderstorm formation, and with the right conditions, tornadoes. The National Weather Service identifies warm, humid ground air, cooler dry air above, and varying wind patterns as conditions that can force tornado development. Paul Markowski, a Penn State University meteorology professor, adds that the stronger the thunderstorm’s updraft — where the air rapidly rises — the greater the potential for severe weather, including tornadoes. Additionally, wind shear, which involves changes in wind speed and direction with height, intensifies the chances of tornadoes forming.
Tornado alerts come in varying degrees of severity. A tornado watch is issued up to 10 hours before a storm by the Storm Prediction Center when conditions are conducive to tornado development over a wide area. Residents should remain vigilant and prepared for further instructions. A tornado warning is issued by local forecast offices when a tornado has been spotted by radar or eyewitnesses and is typically limited to smaller areas like cities or counties. Residents must take immediate actions like seeking shelter in a basement or lowest floor and avoiding windows. The tornado emergency, the most critical alert, is rare but is declared when an already touched-down tornado is causing known catastrophic damage. Immediate sheltering is a must.
Experts stress the importance of having multiple ways to receive weather updates and understand the differences between watches and warnings. Weather radios prove indispensable for weather alerts, especially when power outages render TVs and standard radios useless. Having pre-determined safe, enclosed areas, such as underground or fortified above-ground rooms, is vital in tornado preparation. Many regions prone to tornadoes may lack underground shelter options, so Markowski advises using interior spaces with many walls, like bathrooms, for protection against debris and high winds.
