EF1 Tornado - Enhanced Fujita Scale

The second weakest kind of tornado on the Enhanced Fujita Scale is the EF1. These twisters are stronger, and more destructive than their EF0 counterparts, but are still relatively weak compared to tornadoes on the stronger end of the scale. EF1 tornadoes are characterized by wind speeds ranging from 86 to 110 miles per hour (138 to 177 kilometers per hour) which can inflict substantial damage to life and property.

Meteorologists use damage indicators (DI) to estimate the strength of a tornado. Damage indicators are specific structures, objects, or features that are commonly affected by tornadoes. These indicators serve as reference points for assessing the severity of damage and estimating the wind speeds required to produce such damage. There are 28 total damage indicators which include residential homes, commercial buildings, vehicles, trees, and other infrastructure.

Each damage indicator has 8 degrees of damage (DoD), which rates the amount of damage sustained on an object. Degrees of damage range from just mild damage on the lower end of the scale, to complete destruction. Tornado evaluators, which include meteorologists and civil engineers, use these tools to assess the visible evidence left by a tornado and give it an estimated rating on the EF scale. For weak tornadoes, like EF1s, most damage indicators have only a few (2-3) degrees of damage.

This damage often includes shingles torn off roofs of single-family homes, mobile homes left flipped over, large trees being snapped, and small trees being uprooted. Other damage indicative of EF1 intensity include sheds being blown away, and cars occasionally left turned over. Well-built structures, such as brick homes and commercial buildings, are typically left intact other than roofing and window damage.

Tornadoes of this caliber are less frequent than EF0s, but still common. Between 1950 and 2022, about 33% of all tornadoes reported had and EF1 rating in the United States. Like EF0s, EF1s can occur all over the world but are most frequent in the United States, particularly within Tornado Alley which is located in between the Rocky and Appalachian Mountain ranges. Europe, Canada, and northeastern Mexico also see a relatively high number of EF1s compared to the rest of the world.

Like all tornadoes, EF1s are most likely to form within supercell thunderstorms. However, squall lines, tropical cyclones, and larger thunderstorm complexes are all known to support EF1s. And although these tornadoes can happen year-round, they are most likely to occur in the late afternoon during spring and early summer in the Northern Hemisphere.

The size and duration of EF1s isn’t too different from that of EF0s. They are usually small – only a few hundred yards in base diameter. EF1s do, however, tend to last longer on the ground with an average path of about 3.3 miles often resulting in more damage and loss of life.

An EF1 tornado is much more likely to take your life than an EF0. According to the Severe Weather Database, which records all U.S. tornadoes from 1950-2022, a total of 246 people have been killed by EF1s during this time frame. That’s almost 10 times the amount killed by EF0s. This is mostly due to their increased strength and time on the ground.

A deadly, and very interesting, EF1 in recent history occurred in Osage County, Kansas on June 17, 1978. Around 7 p.m. local time, a severe thunderstorm spawned a tornado just west of Pamona Lake in eastern Kansas. The tornado moved eastward, towards the lake, before reportedly disappearing.

Shortly after the reported disappearance, the tornado reemerged and struck a showboat on the lake named the Whippoorwill. The boat capsized from strong winds before being pushed onshore by the tornado. Of the 58 people onboard, 16 drowned making this the deadliest EF1 tornado in U.S. history.

Although the wind speed of an EF1 is only slightly higher than an EF0, the damage potential is much higher. This is due to a simple law of physics. The force exerted on an object by wind is equal to the product of air density, wind velocity squared, and the area of the object exposed. The fact that wind velocity is squared in calculating force makes a huge difference. This means a 100–mph wind isn’t just twice as strong as a 50–mph wind – it’s 4 times as strong.

You can often survive an EF0 inside a mobile home or RV, but your chances go down significantly in an EF1. A 75-mph wind may shake and rattle a standard mobile home but for the most part, the structure will be left standing in good condition. However, for the same hypothetical mobile home, a 110-mph wind has the potential to roll over or even cause the structure to become airborne. This is all due to the exponential increase of force with wind velocity.

Most mobile homes are suited for winds up to 70 mph. Some manufactured homes, especially along the Gulf Coast where hurricane-proof restrictions are in place, can withstand speeds of 110-mph. Sheltering in a mobile home during a tornado has always been a controversial subject and it often comes down to an in-the-moment decision. It’s important to note that the general consensus is to never shelter in a mobile home during a tornado. Although most mobile structures can withstand weak EF1s and EF0s, tornadoes can rapidly intensify, making these shelters extremely unsafe. Anything over an EF1 in strength will more than likely seriously injure or kill anyone inside.

It's always best to have a tornado safety plan which includes having a well-built structure to resort to in case of an emergency. Examples could be a neighbor's house or a nearby convenience store. If you don’t have these options, it’s recommended to go outside and find the lowest lying part spot in the area surrounding your home. You want to lie face-down, flat on your stomach preferably with some form of body armor and helmet.

The same protocol is recommended if you are driving. Riding out a tornado in a car is again, not a good idea for the same reasons. The best strategy is to pull over, find a ditch, and lie face down until the tornado passes.