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Severe Weather Awareness Week 2020: Tornadoes

Today’s severe weather topic is tornadoes.

During most years, this would be the day of the statewide tornado drill. However, this year it will NOT be conducted. Here is the statement from the National Weather Service in Des Moines:

"Due to the ongoing COVID-19 concerns and the call of social distancing by the Center for Disease Control and Prevention, the National Weather Service (NWS) is canceling Iowa's 2020 tornado drill originally scheduled for 10 AM on Wednesday, March 25th.  Most sheltering locations are in confined spaces, which is not where people should be congregating given ongoing concerns. Another group that we focus on practicing their sheltering is schools and with the majority of those now out of session for the next 4 weeks, the outcome is ineffective."

Tornadoes are one of the scariest weather phenomenons to occur in the world. They are typically short lived but leave a path of destruction. According to the National Severe Storms Laboratory, “A tornado is a narrow, violently rotating column of air that extends from the base of a thunderstorm to the ground. Because wind is invisible, it is hard to see a tornado unless it forms a condensation funnel made up of water droplets, dust and debris. Tornadoes are the most violent of all atmospheric storms.”

Tornadoes need certain atmospheric conditions to form. The simple explanation is there needs to be a temperature difference and rotation near the ground. Check out UCAR for a basic lesson in tornado formation.

Or watch this quick YouTube video:

The United States averages about 1,200 tornadoes per year. Iowa averages 48 tornadoes a year but totals have ranged from just 16 in 2012 to 120 in 2004.

Iowa typically sees the most amount of tornado activity in June. The graphic below shows the amount of tornadoes reported by month since 1980.

NWS Des Moines

Before a tornado strikes, a watch or warning is issued by the local National Weather Service. Sometimes a tornado will strike with little warning but technology continues to improve and the average lead time is 13 minutes. This means, on average, a tornado warning is issued 13 minutes before a tornado may hit an area. Be sure you know the difference between a tornado watch and warning.

On rare occasions, a Tornado Emergency is issued. A tornado emergency should be taken very seriously as a large tornado is confirmed and high impacts are expected. For example, the National Weather Service issued a Tornado Emergency during the Marshalltown tornado in 2018. One was also issued for the 2019 Lee county tornado in Alabama that took the lives of 23 people. A Tornado Emergency is extremely dangerous.

What should you do if a tornado warning is issued for your home? The most important factor is to seek shelter in a STURDY structure.

After a tornado tracks through a town/city/open country, it is given a rating. Ratings are based on the destruction a tornado leaves behind. Before 2007, tornadoes were rated on the Fujita scale. Now they are rated on the Enhanced Fujita scale.

Iowa has only seen six F5 or EF5 tornadoes since 1950.

In 2019, we exceeded the average tornado count when 54 tornadoes touched down across Iowa. Most were unrated tornadoes with no rateable damage.

The National Weather Service in Des Moines issued only a total of 26 tornado warnings while the Quad Cities office issued 33. The offices that issued the most warnings are: Jackson, MS (122) and the New Orleans office (117).

In 2019, we started off very slow with no tornadoes until late in May when we ended up with 25 tornadoes across the state within a week... Fourteen of them all in one day! You can read more about this here.

Today also serves as a reminder to our viewers about our severe weather policy here at KWWL. If a tornado warning is issued for any of the 21 counties we serve, we will be live on air covering up any programming. Our policy will not change.

Don’t be these people:

These were tweets to an Alabama station during the Lee county tornado event that took the lives of 23 people. Lives were likely saved because this station was on air. There will be times we will be able to do a double box of a sports event and tornado coverage BUT safety for you, our viewers, will always be first.

Here are the upcoming topics for the rest of the week:

Thursday: Family Preparedness

Friday: Flash Floods

Eileen Loan

Meteorologist

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