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Planning ahead for tornado season a key to staying safe

First Alert Storm Team Meteorologist Corey Thompson shares information that can help keep you safe from tornadoes during severe weather season in eastern Iowa.
Published: Mar. 23, 2022 at 7:02 PM CDT
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CEDAR RAPIDS, Iowa (KCRG) - Severe Weather Awareness Week continues on Wednesday, with the emphasis being placed on tornadoes and tornado safety.

One theme that connects all of the themed days through this week is that having a plan, well before any severe weather even threatens your area, is an important aspect of staying safe. This applies to tornadoes, as well. Deaths from tornadoes are fairly rare in modern times, thanks largely to a better understanding of the storms that cause them which has increased lead times on warnings. However, not knowing how to respond to a warning can put you in danger.

How a tornado forms

First off, you need a thunderstorm to develop. For this, there are three main ingredients: moisture (water vapor in the air to form clouds), instability (what we often refer to as “energy,” basically an ingredient that allows a cloud to continue building upward), and a source of lift (something to push the air upward to form the cloud in the first place).

An additional ingredient helps to distinguish between a non-severe storm and one that is capable of producing large hail, damaging winds, or tornadoes: wind shear. This is a technical term for a variation in wind speed and direction as you go up in the atmosphere. When correctly aligned, these winds can promote the updraft of a thunderstorm to rotate.

This happens when the wind shear at the lowest levels of the atmosphere (between the ground and a little over half a mile up) causes a slowly rotating column of air that is horizontal, and parallel, to the ground. This rotation is very broad and very subtle, in comparison to the violently-rotating tornado.

A diagram showing wind shear (a difference in wind speed and direction at different heights in...
A diagram showing wind shear (a difference in wind speed and direction at different heights in the atmosphere), which causes horizontal rotation.(KCRG)

As conditions form that allow updrafts to occur, that horizontal rotation can be pulled upward into a developing storm. This tilts the rotation so that it’s oriented vertically, and also stretches it out, making it a narrower column of air. If the updraft rotates, it’s called a “mesocyclone.” A rotating updraft can lead to a storm having more longevity, and higher intensity. It’s also a typical precursor to tornado development.

Horizontally-rotating air near the surface gets pulled upward into a developing thunderstorm....
Horizontally-rotating air near the surface gets pulled upward into a developing thunderstorm. This tilts and stretches it into a vertical position, creating a rotating updraft or "mesocyclone."(KCRG)

That now-vertical rotation can start to extend all the way to the ground, stretching into a narrower column of air. This is where we sometimes use an analogy of a spinning figure skater; as the skater pulls their arms inward to their body (narrowing the width of their rotation), they begin to spin faster. The same kind of idea takes place here: a narrower area of rotation can spin faster. This scales down from the mesocyclone, to a rotating wall cloud (a localized lowering of the cloud base under the updraft), then to the funnel cloud. When the funnel cloud touches the ground, it becomes a tornado.

Watches, warnings, and what they mean

The National Weather Service has the sole responsibility of issuing official watches and warnings, with the former being handled by the Storm Prediction Center in Norman, Okla., and the latter by local NWS offices. In eastern Iowa, offices from Davenport, Des Moines, and La Crosse, Wisc., have responsibility for parts of the TV9 viewing area.

Tornado Watch: These are often issued in advance of the development of storms in your area, and are in effect for several hours at a time. A tornado watch means that the atmospheric conditions are favorable for the development of severe thunderstorms that pose a threat of producing a tornado. When you hear that a watch is issued, you should be considering the following:

  • What is the plan to stay safe in the home? Do members of the household know what to do when a warning is issued?
  • Do I need to leave the house during the watch? It might be a good idea to put off errands, travel, or other avoidable tasks during a tornado watch so that you don’t wind up in a dangerous situation.
  • Do I have a way to receive a warning if one is issued? We will always bring you the latest tornado warnings as soon as possible on KCRG-TV9. But, you should always have multiple ways to receive a warning. Make sure that your NOAA weather radio is plugged in and turned on. Have notifications turned on from the KCRG-TV9 First Alert Weather mobile app. Do not disable Wireless Emergency Alerts on your smartphone. These are basic steps, and websites like KCRG.com, trusted local radio stations, or official sources on social media can also be an additional source to monitor.

Tornado Warning: These are issued for much shorter periods of time, compared to a tornado watch. The shorter-term nature is meant to convey urgency; when a warning is issued, it means that a tornado has been detected by Doppler radar or has been spotted by a weather spotter. You need to take immediate action to protect yourself (see below for more information).

Tornado Emergency: This is a special subset of tornado warnings that are extremely rare. The only situation in recent times to be classified as this by the NWS was the Marshalltown tornado in 2018. Tornado emergencies are only issued in the case of a confirmed, especially intense tornado that is moving into a populated area. These types of warnings mean that you are in a particularly dangerous situation where serious injury or loss of life is possible. You must immediately seek the best possible shelter without delay.

Let’s get down to the most important part: How do I stay safe?

Safety during severe weather requires having a plan and executing it calmly. Taking the right steps when a warning is issued or a tornado is sighted can greatly increase your chances of being unharmed in the unlikely event that a tornado strikes you directly.

If you are at home: The goal is to get as low as possible, as interior as possible to your home. The best place is a basement underground. If you don’t have a basement, the lowest floor of your home in the most interior room is ideal. Putting as many walls between you and the outside will help keep you safe; even relatively weak tornadoes can collapse an exterior wall. Avoid any windows in either situation, which can easily shatter and send glass flying.

Get under something sturdy if possible. A table, desk, or workbench can work. Protect your head and body as much as possible, including using your hands, blankets, pillows, sleeping bags, mattresses, or other sources of cushioning. A helmet can also provide additional protection. Having shoes on your feet will be very helpful if your home is damaged and you need to walk on debris.

If you are in a mobile home: Leave it immediately. Mobile homes are not safe even from the weakest tornadoes. Go to a designated place of shelter as prescribed by your mobile home park, or to a substantial shelter nearby, especially with a basement. If you have a relative, friend, or neighbor who lives very close by in a well-built structure, that can also be a source of safety if you have planned with them ahead of time to seek refuge there. Do NOT plan on being able to safely drive across town to somebody’s house after a warning is issued.

If you are outdoors: If at all possible, get indoors to a sturdy building to seek shelter. If you cannot find a sturdy building in time, then lie flat on the ground in the lowest area possible. A ditch, culvert, or ravine are good spots. Then, cover your head with your hands and arms. Stay away from trees and cars, which can be lifted and blown around by the tornado.

If you are outdoors but driving, do not try to outrun the tornado if it’s close by. In the case that it is very distant, you may be able to avoid it by driving at right angles to the direction that is moving (example: if a tornado is moving east-to-west in the distance in front of you, wait or drive south). If you can find a nearby sturdy building then get into it. If there is low ground that you can safely get to, then abandon your vehicle and follow the directions above. In a worst-case scenario where you cannot avoid a tornado in your vehicle, keep your safety belt on and get as low as possible in the vehicle (below the window line if possible), protecting yourself with any available cover like blankets or coats.

Do NOT stop and park in traffic lanes during this situation, or underneath a bridge or overpass. Bridges offer little to no additional protection, and a gathering of vehicles underneath an overpass can clog a roadway, making an already dangerous situation worse.

If you are at work: Follow established safety guidelines set out by your workplace, which are pretty similar to a home without a basement. Get as low as possible, as interior as possible. Protect your head, neck, and body in the same ways as above. Office buildings often have more glass than a normal home; make sure to avoid those windows as well.

If you are at school: Schools regularly perform drills for tornado safety, so take those seriously and take note of instructions on where to go and what to do. Commonly, an interior hallway that has few windows is safest. Crouch and protect your head. Avoid larger rooms like auditoriums or gyms.

If you are in a mall or large store: Follow directions from store leaders to guide you to a safe shelter. Large, flat-roofed structures can be susceptible to roof collapse, so the open interior of a store is not ideal. In most cases, the store staff will take customers to an interior storeroom, cooler, or other enclosed areas for shelter.

While tornadoes can be frightening, having a plan and knowledge of how to execute it calmly is the best tool to stay safe. Make sure others around you also know what to do, well in advance of severe weather threatening your area.

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