Minnesota Flyer - Serving Midwest Aviation Since 1960

By Dan McDowell
MnDOT Aeronautics 

The Violent Winds

 


Spring brings about changes in nature, the landscape, the weather, and even in people. The warmth of the strong sunshine and more daylight hours are welcomed with open arms. Even the early spring flowers and plants open their buds and spread their tiny petals or leaves like unfolding “wings” raised toward the sky to say ‘thank you’ for the relief from the frost. As the beauty of spring reveals itself in rapidly changing scenes, it is easy to be drawn to the gentleness of the moments along with the subtle, sweet scents of the first flowers. Spring also brings the turbulent clashes of strong atmospheric fronts as they move rapidly to occupy the space of an opposing front.

Each day the sun pours more and more energy into the atmosphere quickly warming the air and the uncovered ground. But in the early part of spring, winter hasn’t yet given up its reign. Often blasts of cold air (a cold front) can move quickly from the north to ram into the growing warm fronts. When that occurs, the differing temperature and pressure gradients of the two air masses can cause violent wind patterns to occur. This violence can manifest itself in several ways including as severe turbulence, or as wind shear. It can also cause the most violent winds regularly experienced in nature, to quickly develop into a rapidly spinning, potentially very destructive vortex called a tornado.

A surprising fact about tornadoes is that they can occur in any season, however they are most likely to occur during the spring and summer months in this region. Tornadoes may be seen as the classic funnel shaped cloud that reaches the ground. While generally easier to see in the daylight hours, tornadoes may be essentially invisible after dark until they strike powerlines, for instance, and a flash of light or even a flash of lightning may for a moment reveal a tornado’s presence. Even in the daylight hours, a tornado can be difficult to see.

Tornadoes that have not touched the ground yet, referred to as funnel clouds, may not have picked up any dust, dirt or debris. Thus they may appear white or as gray as the background. Still others can be hidden behind a cascade of rain that wraps completely around the funnel cloud, thoroughly obscuring it from view. These rain-wrapped tornadoes can and do continue moving in the direction of the parent thunderstorm. It is important to remember that their width and speed across the land can vary greatly at any point in their lifecycle.

Tornadoes have been recorded in every state in the continental United States and also in southern Alaska. Some record sized tornadoes have been shown to be in excess of one mile wide! They can stay on the ground for many miles causing monumental devastation to populated areas in just seconds. The strongest tornadoes can have circulating winds of up to 300 miles per hour, though the most common have winds that vary from 90 to 150 miles per hour.

It is important for everyone to remember that tornadoes can develop very quickly, with little or no warning. Stay weather alert for danger signs including: dark, often greenish sky; frequent lightning; large hail sometimes in the absence of rain; a large, dark, low-lying cloud (particularly if rotating); and a loud roar, like a fast moving freight train. While tornadoes can occur at any time of the day, they most often occur between 3 PM and 9 PM.

Be sure you know where you would go to have the highest available level of protection from a tornado for every place you spend a reasonable amount of time, such as home, work, school, or a place of worship. If and when you see approaching storms or any of the associated danger signs, take shelter immediately! Listen to NOAA Weather Radio or other local alert systems for the latest instructions and emergency information.

After the tornado has passed use extreme caution if you leave your shelter. There may be a multitude of dangerous and sharp objects that could be difficult to see such as clear glass shards, or other dark items if you are leaving the shelter after sunset. Stay away from any powerlines or utility lines. Save your phone for emergencies! As you can imagine, the phone system may be down or extremely busy with emergency calls. If you are OK and want to alert family to that fact, use text messages. Do not start chatting as you could very well be blocking an emergency call from an injured person desperately seeking assistance.

If you are caught at a hangar when a tornado hits, you must know what to do quickly to be safe and protect yourself and others in a matter of seconds. For instance, in a building like a hangar that has no basement, go to an interior room and get under something sturdy like a heavy work bench, if possible. An interior bathroom can be a good choice because the pipes and the walls can provide some amount of extra strength and protection. Stay away from exterior doors and as far away from windows as possible!

The Federal Aviation Administration’s (FAA) FAAST team offer’s this guidance, “Never go closer than 5 miles to any visible storm cloud with overhanging areas, and strongly consider increasing that distance to 20 miles or more. You can encounter hail and violent turbulence anywhere within 20 miles of very strong thunderstorms.” Remember also that a supercell is a single long-lived thunderstorm which is responsible for nearly all of the significant tornadoes produced in the United States and for most of the hailstones larger than golf ball-size. Check AC No: 00-24C for additional information.

Please take the time to properly prepare yourself and your family, because you never really know when you might experience the violent winds!

 

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