Derechos: storms that bring hurricane-force winds
A derecho is a fast-moving line of storms with damaging straight-line winds over hundreds of miles. One reached La Porte County in 2020.
What a derecho is
A derecho is a long-lived windstorm from a fast-moving line of thunderstorms. The National Weather Service describes it as a swath of particularly damaging thunderstorm winds at least 400 miles long and 60 miles wide. The winds are straight-line, not tornadic, but they can top 100 mph, as strong as an EF1 tornado, over a far bigger area.
Has a derecho hit La Porte County?
Yes. The Aug. 10, 2020 derecho, which crossed Iowa, Illinois and Indiana, reached La Porte County in the late afternoon. The Weather Service's Northern Indiana office logged a 56 mph gust 2 miles west-northwest of Michigan City at 4:42 p.m. Central, and a large tree down 2 miles south-southeast of Haskell at 4:48 p.m.
How you get warned
Derechos come with severe thunderstorm warnings, and the Weather Service sends its most destructive severe thunderstorm warnings to phones as Wireless Emergency Alerts. The setup often shows up hours ahead: the Storm Prediction Center's outlooks will show a severe risk over the Midwest, often on hot, humid days.
What to do
- When a severe thunderstorm warning mentions destructive winds, treat it like a tornado warning: get inside a sturdy building, away from windows, on the lowest floor.
- Stay away from trees and power lines, and don't ride it out in a car, camper or tent.
- Expect power outages. Charge phones before storms, and never run a generator, grill or camp stove indoors or in a garage: carbon monoxide is deadly.
Questions
What is a derecho?
A long-lived windstorm from a fast-moving line of thunderstorms, with damaging straight-line winds over a swath at least 400 miles long and 60 miles wide, according to the National Weather Service.
Has a derecho hit La Porte County?
Yes. During the Aug. 10, 2020 derecho, the Weather Service measured a 56 mph gust near Michigan City at 4:42 p.m. Central.
How strong are derecho winds?
They can top 100 mph, as strong as an EF1 tornado, though most gusts are lower.
Will my phone warn me about a derecho?
The Weather Service sends its most destructive severe thunderstorm warnings to phones as Wireless Emergency Alerts. Keep them turned on, and have a NOAA Weather Radio as a backup.
Sources: NWS Northern Indiana: Aug. 10, 2020 derecho · SPC: facts about derechos · SPC: convective outlooks · NWS: Wireless Emergency Alerts · Ready.gov: power outages