Joe’s Weather World: What is a derecho? (TUE-8/11)

Weather

Yesterday was a fascinating day to watch the weather from afar. We had sort of skirted the worst for KC proper…if you read the blog yesterday that didn’t surprise you. There were some strong storms towards the NE of KC…with wind damage up towards the Jamesport area and also down towards Warrensburg. 70 MPH winds were reported there.

By far though the worst was from eastern NE through Indiana. A tremendous complex of thunderstorms developed in SD on Sunday night and moved east south eastwards. As it did so it organized into a massive wind storm. 100+ MPH winds occurred in places and widespread 80+ wind occurred in many areas. These winds weren’t simply in and out..the strong winds lasted for 15-30 minutes as the storms were moving at close to 65 MPH at one point.

This long swath of damage is what we call a “derecho”

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Forecast:

Today: Partly cloudy and seasonable with highs in the mid 80s

Tonight: Fair and muggy…lows in the lower 70s

Tomorrow: About the same with a small chance of some morning storms. Highs in the mid 80s

Thursday: A chance of storms…iffy though for many areas. Highs mid 80s

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Discussion:

Not going to dwell a lot on our weather…we’re sort of in nowhere land for the next couple of days. I can’t rule out rain at some point in typical summer fashion and we need to watch for any disturbances to sneak down from the Plains towards the SE. So it may not be dry for the rest of the week every day although today looks OK for the most part.

Yesterday though…wow!

Almost 800 reports of strong winds or wind damage.

In IA and IL alone almost 1 million customers still without power. Hundreds of trees, if not more uprooted or broken. The corn crop was devastated.

You can see the line of damage just looking at the power outages via poweroutage.us

For farmers…corn was hard hit. It’s was growing pretty good…and can put up a fight to about 70 MPH winds…after that though…it leans over…not to recover from that position.

All because of this.

A derecho is a more specific type of MCS or Mesoscale Convective Complex.

For a derecho (pronounced de-REY-cho) to be labeled that it has to create a swath of damage at least 240 miles long…AND 60 miles wide. That doesn’t happen that often in these thunderstorm complexes.

Winds in IA were 100-112 MPH at their highest (in gusts). There were wide areas of 60-90 MPH winds…essentially the equivalent of a CAT 1 or 2 hurricane. To be fair those hurricanes have sustained winds as a measurement of their strength and these were gusts…but thins wind event was pretty close to what Isaias did as it was moving up the coast…if not more.

It “looked” like a hurricane.

Eventually it weakened as it moves into central MI and OH.

At one point…radar was indicating winds of near 120 MPH aloft, a couple of thousand feet off the ground.

Just an incredible day to watch unfold…all that damage will take weeks to recover from. With all the snapped power poles and lines down…and the trees down…it’s going to take a lot of work to get the grid fixed for all. Crews from around the Plains are heading into that area to help out.

Our feature photo comes from Steve Edwards outside Chillhowee, MO

Joe

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