***Official 2024 Weather Thread***

nfrine

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Mar 31, 2006
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When the 2020 derecho hit, wasn't it only like the second or third one in 20 years or something? Now predictions of derechos seem to get dropped pretty regularly.
We had one in 2011 and 2020 in Marshall County. Don't remember any other storms that were called derechos...but I am very old so I may have forgotten, ;)
 

Trice

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Apr 1, 2010
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https://en.m.wikipedia.org/wiki/List_of_derecho_events

They happen more often than people think, it’s just not a term like tornado that everyone knows

Sorry, I meant in Iowa, not in general. Even on that list there aren't that many in Iowa, and I've seen predictions for possible derechos at least a few times this year alone. So we've either had a sharp increase in conditions for derechos in the span of just a few years, or some forecasters are becoming too reliant on that word.
 
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Hoggins

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Sorry, I meant in Iowa, not in general. Even on that list there aren't that many in Iowa, and I've seen predictions for possible derechos at least a few times this year alone. So we've either had a sharp increase in conditions for derechos in the span of just a few years, or some forecasters are becoming too reliant on that word.

Probably a bit of both, but the earth is also hotter than ever…
 
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clone52

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Jun 27, 2006
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And maybe they can just do it by estimated max wind speed instead of stupid damage assessments.

Well, tornado damage assessments are the best way to estimate the max wind speed of a tornado at ground level. Nowadays, radar might be able to get you an estimated wind speed at elevation, but ground level wind gauges aren't going to give you that kind of data.

Tornado fajita levels are after the fact as well. Its not like you can forecast an individual tornado. Forecast do account for size by saying "large, damaging tornados" or "small spinup tornados" possible.

Hurricanes are slower, so you can forecast what they think it will be in the future.

A derecho could be forecast as well, although I think the VAST majority of Derecho's probably fall into the 58-80mph forecast. We saw one a week or so ago where as it was going and they got wind speed reports over 90, so the bumped up the warnings. But if they did do something like CAT 1=58-70, CAT2 =70-90, etc, it might be easier for people to understand.
 

Gunnerclone

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Jul 16, 2010
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Well, tornado damage assessments are the best way to estimate the max wind speed of a tornado at ground level. Nowadays, radar might be able to get you an estimated wind speed at elevation, but ground level wind gauges aren't going to give you that kind of data.

Tornado fajita levels are after the fact as well. Its not like you can forecast an individual tornado. Forecast do account for size by saying "large, damaging tornados" or "small spinup tornados" possible.

Hurricanes are slower, so you can forecast what they think it will be in the future.

A derecho could be forecast as well, although I think the VAST majority of Derecho's probably fall into the 58-80mph forecast. We saw one a week or so ago where as it was going and they got wind speed reports over 90, so the bumped up the warnings. But if they did do something like CAT 1=58-70, CAT2 =70-90, etc, it might be easier for people to understand.

There’s just one thing that drives me away from damage assessments. And that is the “if a tree falls in the woods does it make a sound?” phenomenon. “If a tornado doesn’t hit a man-made object, was it even a tornado?”.
 
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casey1973

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Apr 20, 2012
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Surprised Ankeny isn't running the sirens yet...

Anyone know of a place my son could park his pickup during the storm? :) He's a student at ISU, but would come to Ankeny. I'm guessing Costco after they close and before they open. Not sure if they monitor or not. He's worried about hail.

If he is in Ames go to the MGMC ramp. My sis has done that with her truck when hail is predicted.
 
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Gunnerclone

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I don't doubt that but even then that seems like a relative explosion in derechos in just a few years.

There’s a reason for that, and it’s the Iowa mega-derecho. Now every Linear severe storm system is a “derecho” to a lot of people.
 

clone52

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Jun 27, 2006
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There’s just one thing that drives me away from damage assessments. And that is the “if a tree falls in the woods does it make a sound?” phenomenon. “If a tornado doesn’t hit a man-made object, was it even a tornado?”.
Thats a fair point, but when it does hit somewhere, damage assessments are the best way to get a wind speed estimate. If it just hits fields and grassland, then we just give thanks and give the best radar estimate.
 

mapnerd

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Aug 17, 2006
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Well, tornado damage assessments are the best way to estimate the max wind speed of a tornado at ground level. Nowadays, radar might be able to get you an estimated wind speed at elevation, but ground level wind gauges aren't going to give you that kind of data.

Tornado fajita levels are after the fact as well. Its not like you can forecast an individual tornado. Forecast do account for size by saying "large, damaging tornados" or "small spinup tornados" possible.

Hurricanes are slower, so you can forecast what they think it will be in the future.

A derecho could be forecast as well, although I think the VAST majority of Derecho's probably fall into the 58-80mph forecast. We saw one a week or so ago where as it was going and they got wind speed reports over 90, so the bumped up the warnings. But if they did do something like CAT 1=58-70, CAT2 =70-90, etc, it might be easier for people to understand.
Tell me more...
 

CY88CE11

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So, when are we expecting this to hit the DSM metro? Seems like it's right around our kids' bed times, so trying to plan ahead in case it gets dicey.
 

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