Radar Analysis of the Greenfield, Iowa Tornado on May 21, 2024

AccuWeather’s Jonathan Porter joined Bernie Rayno on the AccuWeather Network on May 22 to discuss the Greenfield, Iowa tornado that cut a path through that town on May 21, 2024. #greenfield #tornado #radar

They examine the reflectivity, velocity, and correlation coefficient (debris ball signature) radar maps of the destructive and deadly storm.

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[lightthroughdark]

Update: It just got the status of 300MPH+

[carlmay]

DOW twitter states that winds between 250 and 290 were observed only 44m (144’) above ground. Not 600-1, 000’.

[silvershadow]

You can also see the debris spike when it ran over Greenfield. Debris was loftes up to around 40, 000 feet.

[ekojar]

I think it might be upgraded to an EF5 at parts of the track. I saw a photo of a vehicle lift that was ripped out of the concrete, the anchor bolts were still attached to the feet of the lift. And the bolts looked a little bent to me. Not folded completely sideways into L, but not straight. And there was I think 6 bolts per foot.
It had to take a lot of force to pull this thing out and knock it over.
They take the force of vehicles vertically all day long.

The pros will have to survey it though. It could have been something slamming into it that caused it to come out of the concrete. Or its jist not made for horizontal forces. But then you gotta ask. What giant thing was blown that hard to rip this thing out of the ground. Ignore the engendering details for a second. What actually caused this to happen assuming it was anchored properly.

[jakester]

I think this clip would have been 100% better if John was the one doing ALL the talking. He is the chief, right? He's pretty capable of explaining severe weather.
Bernie: "Hey, John, watch this; Hey John take a look at the relative velocity; Hey John watch me do a triple axel; Hey John, big John, big bad John...big John..."

At of the time of this post: The NWS in Des Moines has given this tornado a preliminary rating of EF3. It could change upon completion of survey.

Please, Accuweather, don't allow Bernie to do what he did in this clip. Why have on another person? Ridiculous.

[benwalter]

I think that a tornado should be rated based on a mixture of documented wind speed (the estimation), actual damage caused (the extent), and the overall communal impact (the severity). All these factors should be taken into account/consideration when determining the strength of a tornado; not just solely the severity/ type of damage caused.

[GLING]

I just barely missed this tornado. I was passing through Iowa that day going to visit my son and this tornado had already struck. There was a detour and I think it had to do with tornado damage or an accident. So glad we missed it!

[buckyc.]

I think they need a better system. The Oolagah Ok. Tornado, April. 26, 1991, was two miles wide, but none of the damage was very intense. This one, doesn't appear to be more than 100 yds wide, but the damage looks like it went thru a blender. That lil sucker was INTENSE! Wide doesn't mean all that bad. Andover 1991 was the perfect merger of wide vs intensity. A rare thing.

[AmericanFlyOnTheWall]

Some of that Greenfield damage looked like EF-4 damage.

[screwplanplaybook]

Reed Timmer video of the Greenfield tornado.
Thoughts and prayers for everyone.

[azjaguardesign]

So, it can be an EF-5 in the air, but an EF-4 on touchdown. The ground friction slows it down a tad, I suppose. But, nevertheless ... Still a very powerful cyclone. 🦅

[dustinhallett]

I seen it i live in corning by where it started luckily missed town but damage outside of town and there was a lose of life here as well. Crazy it went all the way to greenfield and did all the damage its sad

[CharlieWeb]

He kept saying that the tornado began here when the blue started appearing on the correlation coefficient data and it very well could have been but the tornado could have been down before that it just hadn't either damaged any structures of trees or it hadn't lofted any debris high enough.

[pauljs]

I'm not sure if many public available radars have some of the filtering or mode tools available like the debris tracker. Although I think there are some things to look for if the radar has enough resolution and frame density in time-lapse mode. I'm not sure of the exact terminology, but I look for a "roller" in the return pattern. Think of it as the sign of a looser vortex that's on its side which moves horizontally with the storm. (Sometimes those are over a hundred miles long.) It's this barber pole banding or sometimes coil banding that moves with the weather pattern. If part of the rolling action is faster relative to the rest, and it gets tighter and kinked up into an S-shape, that's one of the spots to watch out for. I'd guess the speeds of circulation in the roller may be something like 40 to 100MPH aloft, but when it tightens up it's just like an ice skater doing a spin and pulling their arms in. It concentrates all that momentum and then doubles or triples what it starts with. Then if it's an option available through a website, you can do the storm-relative speed thing mentioned in the video to and using the contrast to get an idea of how strong it can be.

If some of those things I'm picturing going on with that bit of information are correct, then calling a tornado a "twister" really is a more than apt description. It's one of those big horizontal vortices folding over into a kink and twisting up upon itself.

[thundersnow]

Their visual products seem rather coarse and crude-looking, compared to simply using the RadarScope app super-res products. I would have thought a TV crew doing post-analysis would have shown more cutting-edge visuals available these days.

[highseas]

I know this was rated EF4, but I have zero doubt that this was an EF5.

[Joshua]

4:13 and yet surveys say there is at least ef3 damage hmmmm

[SunsetSemaphores]

*NOAA while this was happening: Should we issue a Torando Emergency? NAH!!!*

[angrydragon]

I don't understand how this guy is saying this is EF-3 damage when even amateurs know this is catastrophic damage (which is EF-4 or EF-5 damage).

[pickelsvonbrine]

I was hoping there was going to be measurements of for vrot and other stuff. Boo boring. I will take my meteorology from the awesome dudes on twitter.

For those wondering. The DOW or Doppler on wheels was stationed at this tornado. They recorded winds of 290mph at 44m (144ft).