EF4 Tornado - Enhanced Fujita Scale

EF4 tornadoes are characterized by wind speeds ranging from 166 to 200 miles per hour (267 to 322 kilometers per hour). At this level, the destructive potential of these tornadoes becomes extreme, capable of leveling well-constructed homes, tossing vehicles like toys, and uprooting large trees. EF3s are considered “strong” while the National Severe Storms Laboratory considers EF4s to be “violent”.

Due to the exponential increase of force with wind speed, well-built structures, such as brick homes, are left completely destroyed. A safe place in an interior room or closet is often not enough to save your life from tornadoes this violent. It is for this reason that many towns and neighborhoods within Tornado Alley have designated storm shelters. These shelters are often underground, which is really the only place that can keep people safe in tornadoes of this magnitude. Several towns and cities prone to the most violent tornadoes have other infrastructure in place, such as storm sirens which alert residents when there’s a twister on the way.

These tornadoes are extremely rare in most parts of the world. Here’s a map of Europe showing the location of all tornadoes recorded in the European Severe Weather Database. Yellow dots represent EF0s and EF1s, red dots represent EF2s and EF3s, while black dots represent EF4s and EF5s.

As you can see, violent (EF4 and EF5) tornadoes are extremely rare among other, less severe tornadoes. Most occur in northeast France and northern Germany and only during the summer months. Almost all violent tornadoes have occurred in either Europe, or North America although a handful have been reported in counties such as Argentina, Brazil, Uruguay, and Australia. The vast majority of EF4s and EF5s occur in the United States. Here’s a map displaying the individual path of each EF4 tornado in the U.S. from 1950-2019.

A total of 737 EF4s have been recorded between 1950 and 2022 in the United States, far outweighing the 46 recorded in Europe from data that goes back several centuries.

Tornadoes of this caliber are different from their weaker counterparts, and not just in wind strength. EF4s are often much wider and well structured, capable of lasting over an hour on the ground. The average path length of these twisters is 27 miles, and the average base width is 610 yards. These figures are both nearly double that of EF3s. This is part of the reason why 2493 total fatalities have been recorded from EF4s, nearly double that of EF3s despite EF3s being nearly 4 times as frequent.

Violent tornadoes, like EF4s, only occur in supercell thunderstorms. That is, a thunderstorm whose updraft rotates in relation with its downdraft. These storms are usually isolated although they can at times be embedded in squall lines.

EF4 tornadoes usually occur in the late afternoon or evening during the heating of the day. A typical EF4 type day usually starts off calm, sunny, humid, and warm. It becomes warm through the afternoon with the temperature often approaching 90 degrees under partly cloudy skies before the storm arrives. A very good indication of severe weather is puffy cumulus clouds that look slanted like this:

The slant is evidence of wind shear, a critical component of both supercells and tornadoes. If a dryline, or cold front passes through at the right moment (in the late afternoon when heat and instability is greatest) storms will begin popping up. These storms usually stay isolated from one another but form a discrete line along the approaching front or boundary. As long as these storms stay isolated from one another and don’t interfere with their development, they’ll continue to grow. Eventually, with enough wind shear, the storms may turn into supercell thunderstorms capable of creating large violent tornadoes.

There are several other variables that come into play, some of which are still unknown when deciphering which supercells produce tornadoes and which ones don’t. It’s unknown why sometimes, when conditions couldn’t be better, a tornado never forms and other times, when conditions aren’t as good, a violent EF4 develops. However, in general, violent tornadoes usually only occur when there’s maximum instability and vertical shear in the atmosphere.

It's extremely uncommon for everything to come together perfectly to form an EF4. This explains why they only make up less than 1% of all tornadoes within the United States. Despite being so infrequent, these tornadoes have killed many people throughout the United States. In fact, more people have died from EF4s than EF5s.

The deadliest EF4 was the Worchester Massachusetts tornado on June 9th,1953. Because the tornado occurred outside of Tornado Alley, where people are typically more prepared, more injuries and fatalities were reported. 94 deaths and over 1,200 injuries resulted as the tornado ripped through several neighborhoods and a small college where the main tower, which had 3-ft thick brick walls, lost three of its stories. At the time, the tornado was thought to have reached a width of 1-mile with speeds possibly crossing into EF5 territory.

The tornado stayed on the ground for 27 miles before finally lifting near the community of Southborough. It was around this time when the local National Weather Service first issued a tornado warning. By this point, the damage was already done, and the warning had very little meaning or effect. It was soon recognized that if the tornado warning were to have been issued earlier, more lives could have been saved. This event marked a major turning point in how the Storm Prediction Center and the National Weather Service operate. A reorganization was set in place to better prepare people for severe storms. The effort ended up proving successful as only one tornado since then has been more deadly. That is, the Joplin Missouri tornado in 2011.

Over the past several decades, our understanding of severe storms and ability to communicate has improved drastically. Just 75 years ago, nobody had a cell phone, and a lot of people didn’t have TV’s or radio’s either. The internet and social media have drastically enhanced our ability to communicate, and this is one of the biggest reasons why mass casualty tornado events are less frequent today.