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Deadly twister activity already on uptick

| May 4, 2020 1:00 AM

According to an article from The Weather Channel, the U.S. is seeing one of the deadliest tornado seasons in years. There were 73 fatalities from a series of outbreaks in April. Damage from the severe conditions is close to $4.5 billion.

Tornado fatalities for 2020 are already higher than last year, when there was a total of 43 people who were killed by twisters. This year’s figure of 74 is the highest since 2011, when there were 553 fatalities from tornadoes.

This time of year is when we often hear about an increase in tornado activity in the U.S. So far, the Storm Prediction Center says that 453 tornadoes were reported across the U.S. as of May 1. The average is about 780 twisters from January through May, based on a 10-year average.

May is usually the month when we hear about the big tornadoes as we’re in a transitional period for climate. During the spring season, cooler air from the north will collide with warmer air from the south. The Gulf of Mexico also provides a moisture source. This combination, along with a few other factors, sometimes will result in conditions favorable for the formation of tornadoes.

Although the spring season is the most common time for tornado formation, there have been outbreaks at other times of the year, including the winter months. On Feb. 5-6, 2008, a storm system spawned 84 tornadoes that hit the southern U.S. across four states.

The U.S. receives more tornadoes than any other country. In fact, there are four times more twisters here than in Europe.

In recorded history, tornadoes have been seen in all 50 states. In Alaska, there were two twisters reported, one in November of 1959 and the other in August of 2005. Both were on the very low end of the intensity scale. Since 1950, Hawaii has seen 49 tornadoes.

The average number of tornadoes in the U.S. for May is 276, with the majority occurring in Texas (43), Oklahoma (28) and Kansas (38). Both Idaho and Washington average one tornado during the month of May. Last year, a record-breaking 556 tornadoes were spawned in May.

In an average year, there are about 1,200 tornadoes sighted in the U.S. In 2019, there were an estimated 1,676 twisters, which was the fourth-most active season on record. More than 60 percent of all U.S. tornadoes each year occur in what is called “Tornado Alley,” which stretches from Texas and Oklahoma northward through Kansas and eastern Colorado into Nebraska and Iowa.

Fortunately, the Cascade Mountains to the west and the Rockies to the east usually protect us from the extremely powerful thunderstorm activity. But every spring season, and sometimes during the hot summer months, we do see an occasional period of extreme weather conditions.

Tornado intensities are measured using the Enhanced Fujita Scale, with an EF5 being the most destructive. This scale was implemented in early 2007 and has the same design as the original Fujita scale, which included ranges from an F0 to an F5.

Idaho averages three tornadoes per year. One of the worst severe weather and tornado outbreaks ever seen in our region occurred on May 31, 1997, across eastern Washington and northern Idaho. On that day, four F1 twisters hit Stevens and Spokane counties, with one F1 tornado striking Athol in northern Idaho and an F0 spotted near Lewiston. Fortunately, there were no deaths or injuries.

An estimated record 10 tornadoes touched down in Washington and Idaho on May 31, 1997. In Kootenai County, an F2 was reported, one of the largest ever seen in Idaho. An F1 was reported in Jefferson County.

In 2019, there were four tornadoes spotted in southern Idaho and two in western Washington. All tornadoes in Idaho were rated as an EF0. However, on Oct. 18 that year, there was an EF1 twister seen in Mason County, Washington. Our neighbor to the east, Montana, had four tornadoes in 2019. Three were rated as an EF0, but there was an EF1 in Carter County, located in the extreme southeastern portion of the state, on July 18.

In terms of our local weather, April was drier than normal as we had only 0.99 inches of rain, compared to a normal of 1.77 inches in Coeur d’Alene.

The end of this week looks dry and warm across the Inland Empire. Around the middle of the month, we do see an increase in moisture as the strong ridge of high pressure weakens a bit. It’s quite possible that we’ll also see some thunderstorms as well.

Then, we’ll turn dry and warm before more rain arrives around the new moon of May 22. The normal precipitation total for this month in Coeur d’Alene is 2.38 inches. Cliff and I believe we should have rainfall totals near to below normal for May.

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Contact Randy Mann at randy@longrangeweather.com