The 2023 tornado season is off to a deadly start. As of April 1, 2023, the United States has already seen nearly 300 tornadoes — with 84 in March alone, not including the 50-plus tornadoes that occurred the weekend of March 31.
And in the week between March 24 and April 1, at least 45 people died in two separate storm outbreaks that spawned a massive EF-4 tornado in Mississippi.
But what does an EF-4 tornado even mean? And why are a tornado's strength, intensity and damage measured after it hits rather than before, like a hurricane category before it makes landfall?
That brings us to the Fujita Scale, which was developed in 1971 by Dr. Ted Fujita and Allan Pearson to measure the intensity of a tornado. Today, storm experts use an improved version, known as the Enhanced Fujita Scale, which went into effect in 2007. It still measures a tornado's intensity, but it also considers the damage it causes to structures.
The Enhanced Fujita Scale rating system has since been a valuable tool for meteorologists and emergency responders to plan efforts for the aftermaths of extreme wind events.
Rating Tornadoes With the Enhanced Fujita Scale
The National Weather Service (NWS) uses the Enhanced Fujita Scale to rate tornadoes based on their wind speed estimates and the amount of damage they have caused. After a tornado has passed through an area, trained meteorologists will gather data and inspect structural damage to determine the storm's intensity and EF rating.
EF-0: These tornadoes produce gale-force winds of 65 to 85 miles per hour (104 to 136 kilometers per hour), resulting in broken limbs, uprooted shallow trees, and minor damage to gutters, siding and roofing.
EF-1: A "moderate tornado" can cause winds with an average speed of 86 to 110 miles per hour (138 to 177 kilometers per hour). This kind of storm can blow away roof shingles, tip over mobile homes and lightweight structures, and push moving cars off the highway.
EF-2: A "significant tornado" produces wind speeds of 111 to 135 miles per hour (178 to 217 kilometers per hour). These winds are strong enough to cause considerable damage like detaching roofs from homes, blowing over railway boxcars and snapping large, deep-rooted trees.
EF-3: A "severe tornado" will cause total damage to small houses and large structures like schools with wind speeds reaching a blistering 136 to 165 miles per hour (218 to 265.5 kilometers per hour). One of the most dangerous aspects of an EF-3 tornado is it can turn objects as heavy as cars into projectiles.
EF-4: A "devastating tornado" has the power to toss cars and trucks and level entire homes and structures to their foundations with winds of up to 166 to 200 miles per hour (267 to 321 kilometers per hour).
EF-5: An "incredible tornado" has the power to decimate well-built structures and cause significant structural damage to high-rise buildings with winds over 200 miles per hour (321 kilometers per hour). These storms can literally peel the bark off trees and toss cars like they're toys. There have only been 67 EF-5 tornadoes recorded in the world; 59 of those have been in the United States. The last EF-5 tornado to hit the United States was May 20, 2013, in Moore, Oklahoma.
How Tornadoes Are Rated
The National Weather Service is the only federal agency with authority to rate tornadoes with official EF ratings. To give the ratings, it will often use Doppler readings, as well as eyewitness accounts, video footage and photo evidence to craft a meticulous, in-depth model of a tornado's path of devastation.
The NWS then sends the Enhance Fujita Scale rating out to citizens in a public announcement, and the data is passed on to emergency response organizations for high-damage cases. These catastrophic events are rare and make up a small percentage of the roughly 1,000 tornadoes that touch down in the United States every year.
Since 2007, the Enhanced Fujita Scale has been put in practice to increase the accuracy of the original framework. It is compared to a list of Damage Indicators (DIs) and Degrees of Damage (DoD) which offer more detailed hypotheses on top wind speeds during tornadoes and other extreme weather events.
Overall, the Enhance Fujita Scale is an important tool used by the National Weather Service and other meteorological organizations to rate tornadoes and provide critical information to those affected by severe weather events. By understanding the intensity of a tornado and the potential damage it can cause, people can take appropriate measures to stay safe and protect their property during severe weather events.
Now That's Scary
The EF-4 tornado that leveled Rolling Fork, Mississippi, March 24, 2023, occurred overnight, killing 21 people. And a Northern Illinois University study shows that nocturnal tornadoes — those that happen at night when people are sleeping — are more than twice as likely to be deadly compared to those that happen during the day. The study examined 48,000 tornadoes between 1950 and 2005 and found that about one in every 20 overnight tornadoes had deaths, compared with just one in 50 daytime tornadoes.
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