"If you have a storm in motion and it's able to channel atmospheric winds from mid-levels, some really strong winds," said Eric Lenning from the National Weather Service. "It can channel those winds and force them down to the surface along with the motion of the storm. So, we call that straight-line winds because they generally come in and spread out in a straight line."
"It's the same thing like microburst, it comes down and spreads out in an outward type starburst pattern and the winds are moving straight. That would be in contrast to a tornadic circulation where the winds are rotating," Lenning said.
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The National Weather Service said it's also important for people to understand how dangerously strong and high winds can cause widespread damage. "When we put out a tornado warning, a tornado can be much more violent than straight line thunderstorm winds, but it's always going to be over a much smaller area. Straight line winds can be over tens of miles and if you're talking about a Derecho like we had last august that can actually be over hundreds of miles when you factor in the motion of the storm itself," said Lenning.
Hail is another often overlooked yet costly severe weather phenomena. The largest hailstones we saw in 2020 were about 3 inches, bigger than a baseball.
One of the largest hailstones ever reported in Illinois fell near Minooka on June 10, 2015. The hailstone was 4.75 inches in diameter, which is bigger than a grapefruit. Damages in excess of $100,000 were reported with that hailstorm; the cost is real.
"For the insurance industry alone, hail by itself accounts for roughly 50% to 80% of claims in any given year. Obviously, we can have years in which tornadoes are driving a majority of the costs. Or non-tornadic winds like we saw in the Derecho of 2020 which crossed from Iowa into Illinois causing as we know more than $10 billion in damage. So, these can be very costly in addition to what we see on top of additional tornado damage," said Steve Bowen, head of Catastrophe Insight at Aon.
These storms are also happening more frequently.
"The state of the science as far as research done on this topic as far as the last five to 10 years has shown consistently that the frequency of those environments, and in which those environments form will likely increase as we continue our climate change in the future," said Illinois State Climatologist Dr. Trent Ford. "But when we think about the next 50 years or to the end of the century where our climate projections go, what the projections have shown pretty consistently from climate models is that temperature and precipitation change between now and the end of the century are sensitive to greenhouse gas emissions, so we're not stuck on this track. We do still have agency to reduce the overall impact of these events."
With the cost so high and the frequency on the rise, it's more important than ever to have a plan.
Step one: Always have a way to get the latest warnings. The best way to get those current warnings is through a home weather radio or the ABC7Chicago app.
Step two: When the warning is issued, take heed. Head indoors and try to stay away from windows.
Finally, when the severe weather has passed, be careful. If you've lost power there may be live power lines down, and even if the power is not out high winds may snap branches high up in trees that have yet to fall.