• Michael Thornton

How do Thunderstorms, Hail, and Tornadoes work? How can you prepare for it?

Updated: Apr 19, 2020

Hey everyone! Today we are talking about Severe Thunderstorms, Tornadoes, and how you can stay safe during a severe weather event! If you are new to the website, allow me to give some background about myself. My name is Michael Thornton. I have been chasing severe weather for the past 5 years and giving severe weather safety talks to the public for the past 4 years. I am currently taking a Meteorology course at the college I attend and I am majoring in Emergency Management. The reason behind writing a blog that talks about severe weather safety and how Thunderstorms/Tornadoes work, is because I hope that I am able to help those who are not knowledgeable about this subject better understand it.

How does a Thunderstorm form?

For a Thunderstorm to form it needs 3 key ingredients. These ingredients include instability, moisture, and a boundary for the storms to initiate. You may be asking yourself "what is instability?" Instability means that the atmosphere is unstable. When the atmosphere is unstable the temperature will begin to drop significantly as you get higher into the atmosphere. So how do we get Thunderstorms if the air cools down as you increase in height?

Well, during the day the earth's atmosphere heats up because of radiation from the sun. If you have a blue sky on a severe weather day, then the atmosphere will be able to heat up much more quickly because nothing is blocking radiation from getting to the Earth's surface. This is why on cloudy days where severe weather is expected storms might tend to be weaker. After the radiation has reached the ground, conduction begins to occur.

Conduction is the process of the ground transferring the heat from the sun back into the air. Once conduction has completed, the warm air will rise and convection will occur. You may be asking yourself "how can moisture play a role in Thunderstorm development?" Well, simply put, if you have no moisture in the atmosphere, you will get no storms.

The reason for this is because the air will be too dry for storms to form. When the dewpoint is around 55 degrees Fahrenheit storms are able to form more easily and can become severe. Within every Thunderstorm exists an updraft, downdraft, frozen liquid, water, and water vapor. Did you know? Some Severe Thunderstorms can reach as high as 70,000 feet into the atmosphere.

To put that into context planes fly at around 31,000 - 38,000 feet.

What is a Severe Thunderstorm?

A Severe Thunderstorm is a Thunderstorm that is either producing wind speeds over 58mph or hail up to at least 0.75 inches. Severe Thunderstorms can be discrete, meaning that they are by themselves, or they can be multi-cellular, meaning that there is more than 1 storm in the area. Severe Thunderstorms can also come in the form of a squall line. Not all Severe Thunderstorms produce hail, severe winds, and tornadoes. Some just produce hail that can reach up to the size of a softball and others can produce wind speeds up to 100mph.

What is Hail?

Hail occurs when water droplets are carried high into an updraft where the temperatures drop significantly. Hailstones can grow in two separate ways. The first being the "Dry growth". Dry growth occurs when supercooled water and ice crystals collide with each other and then accumulate. The other way is known as "Wet growth".

Wet growth occurs when the ice is in an area where the temperature is below freezing, but not very cold. In this case, when the ice collides with the supercooled water, the water will actually take longer to freeze. Did you know? On July 23rd, 2010, the largest hailstone ever recorded fell in a small town in South Dakota called Vivian. This hailstone measured in at 8 inches in diameter and 18.25 inches in circumference.

What is a derecho, bow echo, and squall line?

Photo courtesy of Josh Swangstu

I know all too well about Derechos, bow echos, and squall lines as I spent the first 18 years of my life in Wisconsin. So what is a squall line? A squall line is a multicellular storm that moves in a linear pattern. Squall lines are usually ahead of the cold front and often intersect the warm front. Now that you know what a squall line is, we can move onto a bow echo. A bow echo is another form of a squall line, but rather than just being linear, they look similar to a bow that you would shoot an arrow with.

1998 Great Lakes Derecho in Wisconsin

Finally, a derecho is the most dangerous type of squall line. It can last for hours spanning across multiple states. A derecho can even cause more damage than a tornado due to its size. In 1998, a derecho formed in Minnesota and move Southeast into Wisconsin where a 120mph wind gust was recorded. This derecho killed 4 people and caused $172 million in damages. To put that into perspective, with inflation that is $275 million today. All squall lines have the ability to be extremely dangerous; please take them seriously!

What is a tornado?

Photo courtesy of StoughtonTornado.org

Before we can talk about tornadoes, we must first talk about what a Supercell is. A Supercell is a Severe Thunderstorm that has a rotating updraft. This rotating updraft acts as a barrier against the environmental wind, meaning that the environment can not destroy the updraft. A Supercell can last for hours and travel across an entire state if it is in the right environment. The life cycle of a Tornado consists of 5 different stages.

Photo courtesy of Dale Bernstein

Those 5 stages are: the dust whirl stage, the organization stage, the mature stage, the shrinking stage, and finally the decaying stage. In the dust whirl stage, the tornado has continuous circulation from the cloud to the ground. The vortex will be invisible as the pressure is not low enough for condensation. So how can you tell if it's actually a tornado or just a funnel? Well, if you see dust being picked up under the funnel then the funnel is in fact actually a tornado.

Photo courtesy of Colin McDermott

During the organization stage, the tornado fully condenses to the ground because the pressure has finally become low enough. During this stage, tornadoes can also rope out and dissipate. When the tornado reaches its mature stage, the tornado is at its most intense. Once the tornado reaches the shrinking stage, the vortex will begin to shrink, while the rotation could actually increase. The tornado will usually take a left path once this process has begun.

Photo courtesy of Cami Rose

Finally, once the tornado has reached the decaying stage the tornado begins to rope out as the RFD (Rear Flank Downdraft) occlusion is completed.

How can you stay safe this severe weather season?

First, if severe weather is forecasted for your area, check the Storm Prediction Center’s website throughout the day. The brilliant minds at the Storm Prediction Center in Norman, OK work hard every day to keep the public informed on possible severe weather days in the United States. They have outlooks that go as far out as 7 days. The SPC even goes into great detail about what you can expect days leading up to and the day of severe weather. Alternatively, you should also listen to your local news station as they will also talk about the potential for severe weather days leading up to and the day of.

Next, you should create a plan and practice that plan in the event of a Tornado Watch/Severe Thunderstorm Watch/Severe Thunderstorm Warning/Tornado Warning being issued for your area. Your plan should include things such as getting to the lowest part of your house, preferably the basement. If you do not have a basement, then get

yourself into the lowest and most interior part of the house. This way you have a bunch of walls surrounding you from the outside. If you have an above ground or below ground storm shelter then that is absolutely great! If you do not have one, consider purchasing one for your home, if possible, as storm shelters have saved thousands of people’s lives. If you live in a mobile home, or a home that isn’t anchored to the ground, you need to abandon it as that home will be obliterated

by the tornado and you could lose your life. But what if you are caught outside and a Tornado Warning is issued for your area? If a Tornado Warning is issued for your area and you are outside, then you need to seek shelter inside a sturdy building immediately, and if possible, get yourself into the most interior part of that building. What if the worst-case scenario occurs and you are out traveling during a Tornado Warning? DO NOT stop your vehicle under a bridge and

hide under the bridge. In 1991, a tornado video surfaced showing people hiding under a bridge and surviving a tornado, but that was only because the tornado didn’t make a direct impact to the bridge. During the May 3rd, 1999, Moore F5 tornado, multiple people hid under a bridge, the tornado went directly over the bridge, increasing the wind speeds resulting in fatalities and serious injuries.

With that being said, again, DO NOT hide under a bridge, rather drive to a sturdy building and seek shelter if possible. If no buildings are in sight, then abandon your vehicle. A vehicle is a guaranteed death trap if you stay in it and a tornado comes over you. That is why you should abandon it and lie flat in a ditch with your hands over your head. This way, if debris was to hit you, your hands would protect your head.

Well, that concludes this blog! I hope that you have learned a thing or two about severe weather and how it works, along with how to stay safe during the severe weather season this year! I truly enjoyed making this blog! So I appreciate you reading it! Be sure to sign up to be alerted when I write my next blog! Once you have signed up you, can also comment on my blogs! Again thank you for reading and have a great day!


Recent Posts

See All