EF3 Tornado - Enhanced Fujita Scale

Next down the list are EF3 tornadoes. A tornado of this magnitude is considered in the severe category, along with EF2s. Winds inside an EF3 can range from 136-165 mph or 218-266 km/h. At this intensity, these tornadoes can cause extensive damage to well-built structures, including the collapse of exterior walls, the destruction of large buildings, and the uprooting of mature trees. These tornadoes often exhibit a distinct and violent funnel shape, accompanied by intense winds and flying debris.

Injuries and fatalities are extremely common when tornadoes of this magnitude hit civilized areas. Since 1950, almost 1400 deaths have been reported from tornadoes of this scale, despite their infrequent nature. This is largely due to the decreasing likelihood of survival outside of an interior room or cellar. Large vehicles, such as trucks and buses, may be able to withstand EF2 winds but are often flipped over and tossed around in wind speeds associated with EF3s. In fact, it’s not uncommon for trains to flip over in 150 mph winds. Large pieces of debris, such as tree branches and outdoor furniture, become flying missiles in winds this powerful. For this reason, your chances of survival outside a “safe spot” are extremely low.

The good thing is that tornadoes of this strength are rare with only 2% worldwide falling into this category. Within the United States, a total 4% of all tornadoes were classified as EF3 from 1950-2022. EF3's and stronger tornadoes, almost exclusively occur in the southeast or central United States, between the Rockies and Appalachian Mountains, and a few isolated regions around the world. Here’s a map of all U.S. EF3s recorded from 1950-2014 courtesy of the University of Nebraska-Lincoln.

Within Europe, the vast majority of EF3's, and all strong tornadoes for that matter, occur in eastern France and Germany. South America has its own tornado alley located in Uruguay and northeastern Argentina. This tornado alley is much smaller, however, than that in the U.S. and tornadoes aren’t as frequent in it. In fact, every continent has its own tornado hotspot, but none of these come close to the activity observed in the Tornado Alley of North America.

So, what makes North America so favorable for tornado activity? Well, geography plays a huge role in the development of tornadoes, especially strong ones like EF3s. If you remember from the previous article, we mentioned that strong tornadoes usually need a lot of time in a consistent environment to develop. A consistent environment suitable for tornadoes includes a steady amount of wind shear, dry air, moisture, instability, and flat level land.

It turns out that the United States is the best place in the world to find all these ingredients. The entire eastern half of the nation, aside from the Appalachian and Ouachita Mountains, is largely flat with little topographic variability. On an even smaller scale, much of the land in Tornado Alley is farmland where disruption from trees and cities is avoided. It’s theorized that part of the reason that the South American Tornado Alley doesn’t see strong tornadoes as often is due to the influence from trees in the southern tip of the Amazon Rainforest.

Although it may seem contrary to what you just read, the size and location of the Rocky Mountains are a huge component in tornado development. Their significant elevation and east-west orientation force air masses to rise on the windward side and descend on the leeward side. This sets the stage for something called Lee Cyclogenesis. Through a series of complex atmospheric processes, an extra-tropical cyclone, also known as a low-pressure system, is generated on the leeward side of the Rocky Mountains. From there, these large cyclones travel east, often bringing rain or snow to the rest of the country.

These low-pressure systems usually pass through the central plains states before drifting northeast toward New England. As they pass through the country, a cold front or dryline is dragged across the central and southern portion of the U.S. where tornadoes are frequent. These fronts bring cold and dry air to a region where there's normally warm humid air already in place from the Gulf of Mexico. This combination, along with instability and shear, provides the perfect opportunity for tornadoes to develop.

A result of this entire process is multiple tornadoes developing across several states as these low-pressure systems can sometimes be thousands of miles across. A tornado outbreak is a common term used to describe when multiple tornadoes develop often across several states. These tornado outbreaks are where EF3 and larger tornadoes are most often found. A single cold front, or dryline, can produce dozen or even hundreds of tornadoes, most of which will be very weak. But in some instances, when local conditions are just right, an EF3 or stronger can develop.

This is exactly what happened in Florida in late February 1998. A powerful low-pressure system moved out of the Rockies, dragging a cold front through the southeastern states. This front clashed with warm humid air from the gulf to produce multiple violent tornadoes over a three-day span (Feb 21 – 23). Several states, including Alabama, Georgia, and Florida, witnessed a multitude of severe weather including deadly tornadoes. This event would later become known as the 1998 Kissimmee Tornado Outbreak which produced at least three EF3 rated tornadoes. Of these three, the deadliest occurred in Osceola and Orange Counties, located in central Florida. This was not only the deadliest EF3, but also the deadliest tornado ever recorded in the state of Florida.

The tornado started off just southeast of Walt Disney World and traveled to the northeast. As it moved forward, the tornado strengthened and eventually hit an RV park where 10 people were killed. The tornado continued its northeastward path, damaging or destroying more homes before entering a rural, uninhabited, swampy area. Unfortunately, the tornado made it all the way across the swampland and met one of the largest RV parks in the country with nearly 1000 vehicle lots according to the local National Weather Service office. In total, this singular tornado took 25 lives and damaged close to 1000 structures costing $55 million in 1998 dollars. Of all the tornadoes included in this outbreak, 42 fatalities were recorded.