In some parts of the world, especially in the United States, tornadoes – sometimes called “twisters” – can pose a danger to travelers.
A tornado is a spinning column of very low-pressure air, which sucks the surrounding air inward and upward. They generate high winds (often 100-200 miles/hour) and can lift heavy objects into the air, carrying them as the tornado moves. They begin as funnels descending from storm clouds, and become “tornadoes” when they touch the ground. Unlike hurricanes, tornadoes develop very quickly, giving little advance warning that one is coming (minutes at most), but they are also very short-lived, likewise lasting only a matter of minutes each. They frequently occur in clusters, with several tornadoes striking an area around the same time.
Compared to a cyclone (hurricane or typhoon), a tornado is much more concentrated. While cyclones are generally at least dozens of miles across and sometimes hundreds, it is quite rare for a tornado to be even one mile wide.
About 1,000 tornadoes are reported each year in the US, but only a small percentage of those touch down and strike buildings. Also, less than 30% of the tornadoes that occur are significantly powerful (EF2+). Most deaths occur to occupants of mobile homes and cars. Tornadoes can occur any time during the year, but they are most frequent in the spring and early summer, in thunderstorm weather. Keep in mind that as a short-term visitor, the odds of you being in the wrong place at the wrong time to face a tornado are quite small, regardless of when and where you travel. But it’s good to be prepared.
The area where tornadoes occur most frequently is dubbed “Tornado Alley”. Tornado Alley is in the Great Plains region of the United States. It includes north Texas, Oklahoma, Kansas, Nebraska, and eastern South Dakota. But tornadoes can develop anywhere cool dry air and warm moist air intermix, and powerful tornadoes happen fairly often in the Midwest, the South, and to a lesser extent the Mid-Atlantic. The western side of the US experiences tornadoes too but with far less activity than the eastern half of the US. Tornadoes also occur in Canada, but less frequently, and they happen in other countries as well. In fact, the Netherlands has the highest rate of tornadoes for its small land area.
Preparedness involves knowing the major dangers to avoid. Some tornadoes are the most violent storms in nature. Tornadoes have varied in strength, and some tornadoes have been mostly invisible due to a lack of loose dirt or debris in the funnel cloud. Spawned from severe thunderstorms, tornadoes have caused fatalities and devastated neighborhoods within seconds of arrival.
A tornado operates as a rotating, funnel-shaped cloud that extends downward from a thunderstorm, to the ground, with swirling winds which have reached 300 miles per hour (480 km/h). The wind speed might be difficult to imagine: traveling the length of a U.S. football field within 1 second (over 130 meters or 430 feet per second). Damage paths have been in excess of one-mile wide (1.6 km) and 50 miles long (80 km).
Not all tornadoes are easily seen. A tornado funnel can be transparent until reaching an area with loose dirt and debris. Also, some tornadoes have been seen against sunlit areas, but rain or nearby low-hanging clouds has obscured other tornadoes. Occasionally, tornadoes have developed so suddenly, so rapidly, that little, if any, advance warning was possible.
Before a tornado strikes an area, the wind has been known to die down and the air to become very still.[dubious – discuss] A cloud of debris has sometimes marked the bottom of a tornado even when the funnel was not visible. Tornadoes typically occur along the trailing edge of a thunderstorm.
The following is a summary of typical tornadoes:
They may strike quickly, with little or no warning.
They may appear nearly transparent until dust and debris are picked up or a cloud forms in the funnel.
The average tornado moves Southwest to Northeast in the U.S., but tornadoes have been known to move in any direction.
The average forward speed of a tornado is 30 miles per hour (48 km/h), but has varied from stationary to 70 mph (110 km/h).
Tornadoes can also accompany tropical storms and hurricanes as they move onto land.
Waterspouts are tornadoes that form over water.
Tornadoes are most frequently reported east of the Rocky Mountains during spring and summer months.
Peak tornado season in the southern U.S. states is March through May; in the northern states, it is late spring through early summer.
Tornadoes are most likely to occur between 3 p.m. and 9 p.m. (local time), but have occurred at other times.
Steps when expecting storms to arrive
The U.S. Federal Emergency Management Agency (FEMA) has advised the following precautions before a storm reaches an area:
Be alert to the changing weather conditions.
Listen to NOAA Weather Radio and/or Skywarn, or to local commercial radio or television newscasts for the latest information.
Watch various common danger signs, including:
dark, often greenish-colored sky;
large hail stones;
a large, dark, low-lying cloud (particularly if rotating);
loud roar of wind, sounding similar to a freight train.
Upon seeing an approaching storm or noticing any of the danger signs, they were advised to prepare to take shelter immediately, such as moving to a safe room, internal stairway, or other safe-haven area.
All individuals and families should have a disaster preparedness kit made prior to tornado. According to FEMA the kit should include items needed to shelter in place in the event of a disaster such as a tornado for up to 72 hours following impact.
Despite their rapid development, tornadoes do not strike entirely without warning. Meteorologists can identify conditions right for tornadoes to develop, and the U.S. National Weather Service issues two main alerts for them (with confusingly similar-sounding names):
Tornado Watch – This indicates that conditions are right for tornadoes, but none has been observed. Monitor conditions and listen for further alerts.
Tornado Warning – A tornado or funnel cloud (a precursor to a tornado’s touching down) has been spotted or is indicated by radar. This is when tornado sirens may begin. Seek shelter immediately. When a powerful tornado is headed for a densely populated area, the NWS issues a Tornado Emergency to stress the severity.
Some local areas have tornado sirens and lights, especially in Tornado Alley and other regions where tornadoes are a seasonal occurrence. If you hear what sounds like an air raid siren, this is probably a tornado siren sounding, and you should seek shelter immediately. Many communities periodically test these systems at a set time, such as at exactly noon on a weekday of the first week of each month, so check the time and the skies (tornadoes do not develop in sunny weather) before panicking. (Most communities will skip these tests if the weather is stormy, to avoid causing undue alarm.)
Heavy rain and hail can hide a tornado from view. This is especially likely in the more humid regions of the southern and eastern US. Tornadoes will also be very difficult to see at nighttime, unless backlit by frequent lightning. The roar of a tornado (similar to a freight train or a jet aircraft taking off) may be the only sign that one is approaching.
There are some specific signs that a tornado is developing or likely:
Debris – If you see a cloud of debris being swept into the air in the distance, that could mark the position of a tornado even if you don’t see the funnel cloud.
Green Clouds – Green clouds are normally seen when there is a large amount of ice in the clouds. This is an indication of hail and could be a warning that a tornado is likely.
Hail – Hail will sometimes occur. The larger the hail the more likely that there may be a tornado associated with the storm.
Rotation – If you see rotation in the clouds (not just a swirl of wind near ground level, which is an entirely different phenomenon), that may indicate the presence of a tornado or the possibility of a tornado developing.
Day or night, A loud continuous roar or rumble which doesn’t fade in a few seconds like thunder or a train could indicate a tornado.
WARNING: Do not take shelter under a bridge, most notably an underpass or overpass! People have been killed and/or seriously injured trying this, due to flying debris funneled under the bridge. The winds from the tornado tend to be stronger under the bridge, which shows that a bridge is not at all a good idea for shelter from a tornado.
In the event of a tornado, please forget that you’re a camera-wielding tourist. Don’t try to snap photos to document your big adventure. Don’t try to retrieve your luggage. Just get yourself to safety immediately.
Actions taken during tornadoes
During August 2010, FEMA advised people to perform the following actions when a tornado struck.
|In a structure (e.g. residence, small building, school, nursing home, hospital, factory, shopping center, high-rise building,restaurant)||They were to enter a pre-designated shelter area such as a safe room, basement, storm cellar, or the lowest building level. If there was no basement, then to the center of an interior room on the lowest level (closet, interior hallway) away from corners, windows, doors, and outside walls. The goal has been to put as many walls as possible between there and the outside. They were advised to get under a sturdy table and use arms to protect head and neck, and not open windows.|
|In a vehicle, trailer, or mobile home||They were advised to leave immediately and enter the lowest floor of a sturdy, nearby building or a storm shelter. Mobile homes, even if tied down, offer little protection from tornadoes. If a car is flipped by high winds, there is also the danger of broken glass.|
|On the outside with no shelter||They were advised to lie flat in a nearby ditch or depression and cover head with their hands. Also, to beware of the potential for flooding there.
They were advised to not stay under an overpass or bridge (where winds or debris might be funneled). It was safer to be in a low, flat location.
The advice was to never try to outrun a tornado in urban or congested areas in a car or truck, but instead, to leave the vehicle immediately for safe shelter.
Flying debris from tornadoes causes most fatalities and injuries.
Because some preparations vary, depending on location, people have been advised to consult their local area preparedness plans, rather than assume the plans are similar for all areas, such as which local buildings have been designated as storm shelters.
A 2012 study of tornado injuries found that wearing a helmet such as those used for American football or bicycling, is an effective way to reduce injuries and deaths from head trauma. As of 2012, the CDC endorsed only general head protection, but recommended that if helmets are to be used, they be kept close by to avoid wasting time searching for them.
After the 2013 Moore tornado, it became apparent that thousands of people attempt to flee major tornadoes, and this has been credited with reducing the death toll. However, during this event some people were killed as the tornado passed over the traffic jam caused by the impromptu evacuation. In addition to urban traffic, evacuation can also be hampered by flash flooding produced by associated thunderstorms, and the need to be certain about the position and direction of the tornado. Others who did not flee the Moore tornado were also killed because the buildings they were hiding in were completely destroyed, highlighting the need for storm shelters and safe rooms constructed specifically to withstand very high winds.
The safest place to be is in a storm shelter or safe room built specifically for a tornado safety. In tornado areas these are found frequently in or near rural homes and mobile home parks. The most important thing is not to panic. Stay calm and find the safest area you can get to quickly.
If you are in a house, get away from the windows (which will probably shatter) and go to the lowest floor. If there is a basement, go there and get under something such as a bench or table. If there is no basement, go to a center room with no windows, such as a closet or bathroom. If in the bathroom, lie down in the tub. Crouch down and if you have some padding such as a mattress to protect you from flying or falling debris, put that over you. Do not waste time that can be better spent getting to shelter by trying to open windows to prevent them from breaking.
Go to the lowest floor or center of the building away from windows and close to an interior wall. Crouch down and cover your head. Do not get in the elevator; you’ll be trapped if the electricity goes out, and there’s always a chance that the lift mechanism will give out if the roof is damaged. If you’re not too high, use internal stairways to reach the ground floor or basement. Stairwells are probably one of the safer places to seek shelter in such circumstances anyway (i.e. no windows, sturdy construction).
The least safe place to be is inside something the tornado can pick up; you’re actually better off outside.
If you are in a mobile home and there’s a tornado warning, you should seek out the nearest storm shelter or protected building. People morbidly joke that mobile homes and trailers must somehow attract tornadoes because they are so often shown on TV as twister disaster areas; the serious truth is that their vulnerability is why they make for the most sensational news clips. Studies have shown that a mobile home is the worst place you can be during a tornado; the broad sides of the structure are like a sail in the wind, and there’s nothing to hold them in place. It may sound counterintuitive, but you should leave the mobile home and get in a ditch, culvert, or drain pipe, low to the ground. If you are staying in a mobile home and trailer park ask management if there is a tornado shelter close by. These may be cellars or sturdy buildings.
If you are in your automobile and you see a tornado coming, don’t try to out-run it; tornadoes can easily outrun a car driving into a 100-mph headwind. Your safest option is to leave the car and get in a sturdy building. If that is not available, get out of the car and get in a low area such as a culvert, drain pipe or ditch. If you are staying in your car, attempt to drive at right angles to the tornado to get out of its path. If the tornado does not appear to be moving left or right, chances are it is coming straight for you. A car is probably safer than a mobile home (less wind-catching surface to drag it into the air), but it’s still safer to get out and hunker down low. The best option is to find a ditch to lie flat in, and cover up.
After a tornado
Watch out for sharp objects and downed power lines. Do not stand in water where there are power lines down. Stay out of heavily damaged houses and buildings as there may be a danger of collapse. Lighters and matches should not be used as there may be a danger of gas leaks. Remain calm and wait for instructions from local emergency personnel.
Depending on location, various safe-haven areas have been prepared. The goal has been to avoid outer walls which might collapse when a roof section becomes airborne and the walls below lose their upper support: many interior rooms resist collapse longer, due to smaller walls interconnected to each other, while outer walls deflect the force of the winds. Because mobile homes typically lack foundation anchors and present a large surface-area sail (to catch wind), the advice has been to seek a safe haven elsewhere, such as in a stronger nearby building. When a mobile home begins to roll, people have been injured by hitting objects inside, or being crushed when a trailer suddenly hits the ground and begins to collapse around them.
In a multi-story building, an internal stairway (away from broken windows) often acts as a safe haven, due to the stairs reinforcing the walls and blocking any major debris falling from above. If a stairway is lined with windows, then there would be the danger of flying glass, so an interior stairway, or small inner room, would be preferable.
In private homes, some similar stairway rooms have been used, or an interior room/closet kept clear to quickly allow entry when a storm is seen or heard approaching (the wind roar intensifies, sounding like a swift “freight train” coming nearer, louder). With weeks or months to prepare, an interior safe room can be constructed, with space for emergency water, food and flashlights, and a telephone to call for rescue if the exit becomes blocked by falling debris. Some above-ground safe rooms have been built with steel-rebar rods in cement-filled cinder blocks, to withstand winds of 250 miles per hour (400 km/h). Rural homes might have an outside storm cellar, or other external bunker, to avoid being trapped within a collapsing house. In rural homes, generators are also helpful to maintain power with enough fuel for a few days.
There were no building codes requiring tornado shelters nor specifically designed to prevent tornado damage until the 2011 Joplin tornado prompted a local ordinance requiring hurricane ties or similar fasteners. The state of Oklahoma adopted the minimum U.S. standard that year for the first time, but did not add high-wind protections like those in Florida designed to protect against hurricanes. Other states in Tornado Alley have no statewide building codes. The chance of any given location in Tornado Alley getting hit by an F-2 tornado (strong enough to do major structural damage and exceeding the 90 mph guideline for straightline winds) is about 1 every 4,000-5,000 years; in other areas the annual probability is one in several million. The most stringent building codes only require earthquake strengthening for a 1 in every 500-1,000 year probability.
The U.S. Federal Emergency Management Agency has spent tens millions of dollars subsidizing the construction of shelters and safe rooms in both private and public buildings. Many buildings in Tornado Alley do not have basements, because unlike in more northern areas, there is no need for a deep foundation to get below the frost line, in some places the water table is high, and expansion and contraction of clay-heavy soils can produce additional pressure on buildings that can cause leaks if not reinforced.
Having a first aid kit in the safe haven is advised to help victims recover from minor injuries. People needing prescription medications could have a medicine bag ready to take to shelter. Some people have reported their “ears popping” due to the change in air pressure, but those effects seem to be temporary. Covering people with mattresses or cushions has helped avoid injury from flying debris, as walls collapsed nearby.
Injuries sustained during a tornado vary in nature and in severity. The most common injuries experienced during a tornado are complex contaminated soft tissue wounds and account for more than 50% of the cases seen by emergency rooms following a tornado. These wounds will most likely be contaminated with soil and foreign bodies due to high wind speeds caused by tornadoes. Fractures are the second most common injury obtained after a tornado strikes and account for up to 30% of total injuries. Head injuries are also commonly reported during a tornado, but severe head injuries only account for less than 10% of the total. Even though only 10% of reported head injuries are severe, they are the most common cause of death following a tornado. Blunt trauma to the chest and abdomen are also injuries obtained following a tornado, but only account for less than 10% of overall injuries.