How To Identify A Tornado & What To Do If One Occurs

What is a tornado?

A violently rotating column of air or pendant which extends from the base from a cumulonimbus cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud. By definition, a tornado has to be “on the ground”. If a tornado has not touched the ground, it is classified as a funnel cloud.

Tornadoes form in unusually violent thunderstorms where there is significant instability and wind shear in the lower atmosphere. They also appear as a funnel clouds from the base of cumulonimbus (CB) cloud and/or a swirling cloud of dust or debris rising from the ground. Tornadoes usually appear in the right rear area of of the CB. Where the inflow is entering the storm updraft core. The wall cloud usually represents the area of the updraft.

Warm and moist or humid conditions in the lower levels and cooler than usual conditions in the upper levels make for unstable conditions. The change in wind direction and an increase in wind speed with height is referred to as wind shear. For example a surface wind of 20 knots from the south changing to a southerly or westerly flow at 50 knots at 5,000 feet would be significant enough of a change to cause wind shear.

Wind shear is the main reason tornadoes are so destructive. Calm wind usually is observed before the onset of a tornado (calm before the storm). In a matter of seconds, the wind can go from 0 to 200 mph. Directional wind shear of 360° occurs is a matter of seconds when a tornado moves across a structure. The intense spinning of a tornado is partly the result of the updrafts and downdrafts in the thunderstorm (caused by the unstable air) interacting with the wind shear, resulting in a tilting of the wind shear to form an upright tornado vortex.

With the storm already rotating in the counter-clockwise direction (in the northern hemisphere), the winds then converge inward toward the storm and this causes it to spin faster.

Other factors that make a tornado so destructive are the Bernoulli Effect and Over-Pressurization.

Tornado Movement – The movement of a tornado is governed by the movement of the parent storm. Tornadoes often move in a circular pattern under the parent storm and the smaller scale speed is often controlled by tornado motion under the parent storm. Average movement of tornado is from Southwest to Northeast with an average speed of 30 mph.

Preparing For A Tornado

Preparation for severe weather should be considered no matter where you may live. Some areas are more prone to tornadoes than others and it seems more tornadoes are occurring and their intensity is getting worse. Everyone whether at home or work should have a plan in place and be prepared to take action if the need ever arises.

It is important to know is the difference between a tornado watch and a tornado warning. A tornado watch is when there is the potential for a tornado to develop from a thunderstorm in the area and that a tornado has not been sighted or detected by radar. A tornado warning is when there has been a tornado spotted on the ground or rotation has been detected by radar.

Prevention & Practice Before The Storm

At home, have a family tornado plan in place, based on the kind of dwelling you live in and the safety tips below. Know where you can take shelter in a matter of seconds, and practice a family tornado drill at least once a year. Have a pre-determined place to meet after a disaster.

The greatest danger during a tornado is flying debris. If at all possible, keep thick blankets or even some sleeping bags or a mattress near your shelter place.

When a tornado watch or warning is issued, get to your shelter place and turn on a TV or radio to keep up on the latest developments and warnings. If you are at work or a local store, keep in mind they should have locating within the building for tornado shelters. These places are typically the bathrooms or interior storage areas. Know where these locations are and the shortest route to get there. Most shopping centers and arenas should have a tornado safety plan already in place.

Signs Of A Tornado

Weather forecasting is not a perfect science and some tornadoes do occur without a tornado warning. There is no substitute for staying alert to the sky. Besides an obviously visible tornado, here are some things to look and listen for:

1. Strong, persistent rotation in the cloud base.
2. Whirling dust or debris on the ground under a cloud base — tornadoes sometimes have no funnel!
3. Hail or heavy rain followed by either dead calm or a fast, intense wind shift. Many tornadoes are wrapped in heavy precipitation and can’t be seen.
4. Day or night – Loud, continuous roar or rumble, which doesn’t fade in a few seconds like thunder.
5. Night – Small, bright, blue-green to white flashes at ground level near a thunderstorm (as opposed to silvery lightning up in the clouds). These mean power lines are being snapped by very strong wind, maybe a tornado.
6. Night – Persistent lowering from the cloud base, illuminated or silhouetted by lightning — especially if it is on the ground or there is a blue-green-white power flash underneath.

Severe thunderstorms can reach height of over 40,000 feet and the base ceiling lower than 1,000 feet. It is very difficult to see the inner workings of a thunderstorm from the surface, that is why we depend on radar to detect any rotation in the upper levels that can give us a warning to prevent loss of life. Most local areas have the warning sirens in effect and these warnings should be noticed.

If a watch or warning goes into effect in your area, the are steps you can take to get a head start on safety. The first step in preparing for a tornado is to know the location within your house to take cover. Location should be be discussed with everyone in the household and be set as the designated meeting place in case of a warning. A basement to the safest place to go if you have a basement available. The next best place is a crawl space followed by a doorway or in the bathtub. Another place would be under a sturdy table.

Although rare, tornadoes can be strong enough to remove complete structures and anyone in them.

No matter where you live, you are at risk for a tornado. All of the fifty United States have fallen victim to tornadoes before. Even if the tornadoes that do strike your area are small or low in intensity, it is still best to be prepared.

Places To Consider For Shelter

Falling and flying debris is the most common cause of deaths and injuries during a tornado. Although there is no completely safe place during a tornado, some locations are much safer than others.

In a house with a basement: Avoid windows. Get in the basement and under some kind of sturdy protection (heavy table or work bench), or cover yourself with a mattress or sleeping bag. Know where very heavy objects rest on the floor above (pianos, refrigerators, waterbeds, etc.) and do not go under them. They may fall down through a weakened floor and crush you. Head protection, such as a helmet, can boost survivability also.

In a house with no basement, a dorm, or an apartment: Avoid windows. Go to the lowest floor, small center room (like a bathroom or closet), under a stairwell, or in an interior hallway with no windows. Crouch as low as possible to the floor, facing down; and cover your head with your hands. A bath tub may offer a shell of partial protection. Even in an interior room, you should cover yourself with some sort of thick padding (mattress, blankets, etc.), to protect against falling debris in case the roof and ceiling fail. A helmet can offer some protection against head injury.

In an office building, hospital, nursing home or skyscraper: Go directly to an enclosed, windowless area in the center of the building — away from glass and on the lowest floor possible. Then, crouch down and cover your head. Interior stairwells are usually good places to take shelter, and if not crowded, allow you to get to a lower level quickly. Stay off the elevators; you could be trapped in them if the power is lost.

In a mobile home: Get out! Even if your home is tied down, it is not as safe as an underground shelter or permanent, sturdy building. Go to one of those shelters, or to a nearby permanent structure, using your tornado evacuation plan. Most tornadoes can destroy even tied-down mobile homes; and it is best not to play the low odds that yours will make it.

At school: Follow the drill! Go to the interior hall or windowless room in an orderly way as you are told. Crouch low, head down, and protect the back of your head with your arms. Stay away from windows and large open rooms like gyms and auditoriums.

In a car or truck: Vehicles are extremely risky in a tornado. There is no safe option when caught in a tornado in a car, just slightly less-dangerous ones. If the tornado is visible, far away, and the traffic is light, you may be able to drive out of its path by moving at right angles to the tornado. Seek shelter in a sturdy building, or underground if possible. If you are caught by extreme winds or flying debris, park the car as quickly and safely as possible — out of the traffic lanes. Stay in the car with the seat belt on. Put your head down below the windows; cover your head with your hands and a blanket, coat, or other cushion if possible. If you can safely get noticeably lower than the level of the roadway,leave your car and lie in that area, covering your head with your hands. Avoid seeking shelter under bridges, which can create deadly traffic hazards while offering little protection against flying debris.

In the open outdoors: If possible, seek shelter in a sturdy building. If not, lie flat and face-down on low ground, protecting the back of your head with your arms. Get as far away from trees and cars as you can; they may be blown onto you in a tornado.

In a shopping mall or large store: Do not panic. Watch for others. Move as quickly as possible to an interior bathroom, storage room or other small enclosed area, away from windows.

In a church or theater: Do not panic. If possible, move quickly but orderly to an interior bathroom or hallway, away from windows. Crouch face-down and protect your head with your arms. If there is no time to do that, get under the seats or pews, protecting your head with your arms or hands.

Gathering all needed supplies is another one of the many ways that you can prepare for a tornado or at least tornado season. If your above mentioned tornado preparation plan involves retreating to your basement, you will want to gather your supplies and store them there. If your plan involves retreating into an interior room, you will still want to gather all needed supplies, but store them nearby, such as in a nearby closet or cabinet. The supplies that you may want to have on hand include a little bit of water, non-perishable snacks, such as crackers, as well as a weather radio and working flashlights.

As previously stated, it is advised that you have a weather radio, especially if you live in “Tornado Alley.” Weather radios have broadcast weather announcements and alerts, especially during severe weather. These updates and alerts can, literally, be lifesaving for those in the middle of tornado activity. In addition to standard battery operated weather radios, you can also purchase those that include a built in clock, AM/FM radio, as well as a flashlight. Weather radios can easily be purchased, for an affordable price, from most sports stores, department stores, as well as online.

The above mentioned preparation steps are just a few of the many that you may want to take, should you live in an area that sees its fair share of tornadoes. As a reminder, it is important to always stay updated on what is happening outdoors. In many areas, especially the Midwest, a simple thunderstorm can spawn a tornado, often times in a matter of minutes. For that reason, you will always want to keep your eyes and ears open.