Severe WX Historic April 27-May 1 2024 Midwest Storms

[TH2002]

Farm field swept clean by the Hollister tornado.

 

[buckeye05]

I think we are getting ahead of ourselves here a bit. We saw plenty of “violent” returns from Nebraska and Iowa Friday and all yielded EF3s so far.



The scouring plus lofting and throwing an entire mobile home a pretty good distance without it ever touching the ground. It also swept a house, but not sure on its construction. @buckeye05 would probably know the answer on why it got an EF5 better than I would.

So believe it or not, the EF5 rating in Philadelphia was based entirely on the extremely deep ground scouring. I actually remember the whole rating and upgrade process as it happened. It was initially rated EF4, however, NWS Jackson was later notified about deep plowing of the earth in a pasture on a rural property somewhere. So the NWS Jackson survey team went out a second time, found the crazy deep scouring, and decided to bump the rating from EF4 to EF5.

Here's where it gets problematic, this phenomenon has since been documented in other tornadoes that were NOT of EF5 intensity. A minimal EF3 deeply plowed up the earth near Clarks, LA on November 29, 2022. Even more shocking, a clearly weak EF1 tornado produced this type of scouring near Mauk, GA earlier that year on April 5, 2022. After looking at ground scouring photos over the past decade, I have actually concluded it's a different type of scouring that is more closely-correlated with the most violent of tornadoes. The best way I can describe it when you have a swath of most or all grass/surface vegetation removed along an even but sharply defined contour. The result is a smooth, flat trail of mostly bare soil. The best example of this can be seen in Bridge Creek 1999, but is also apparent in Moore 2013, Vilonia 2014, Rochelle 2015, Chickasha 2011, Goldsby 2011, El Reno 2011, and most recently, Matador 2023. There's other examples too, but either way, I believe the days of scouring-based EF5s are long over.

Sorry if that got long-winded. It's a subject I am passionate about.

 

[Maxis_s]

and most recently, Matador 2023

I still do not understand how on earth this was rated only an EF3 but that's a discussion for another time.
Philadelphia's ground scouring was trenches of over 2 feet deep. Weak tornadoes can sometimes scour some ground but nowhere near 2 feet deep and absolutely not in a wide, continuous swath.
Anyways, does anyone know if someone is going to visit the tornado's path to check for damage, or are we gonna have to wait more?

 

[cincywx]

So believe it or not, the EF5 rating in Philadelphia was based entirely on the extremely deep ground scouring. I actually remember the whole rating and upgrade process as it happened. It was initially rated EF4, however, NWS Jackson was later notified about deep plowing of the earth in a pasture on a rural property somewhere. So the NWS Jackson survey team went out a second time, found the crazy deep scouring, and decided to bump the rating from EF4 to EF5.

Here's where it gets problematic, this phenomenon has since been documented in other tornadoes that were NOT of EF5 intensity. A minimal EF3 deeply plowed up the earth near Clarks, LA on November 29, 2022. Even more shocking, a clearly weak EF1 tornado produced this type of scouring near Mauk, GA earlier that year on April 5, 2022. After looking at ground scouring photos over the past decade, I have actually concluded it's a different type of scouring that is more closely-correlated with the most violent of tornadoes. The best way I can describe it when you have a swath of most or all grass/surface vegetation removed along an even but sharply defined contour. The result is a smooth, flat trail of mostly bare soil. The best example of this can be seen in Bridge Creek 1999, but is also apparent in Moore 2013, Vilonia 2014, Rochelle 2015, Chickasha 2011, Goldsby 2011, El Reno 2011, and most recently, Matador 2023. There's other examples too, but either way, I believe the days of scouring-based EF5s are long over.

Sorry if that got long-winded. It's a subject I am passionate about.

does the composition of the ground have an impact? I would imagine (purely conjecture) that soft soil is lighter and more susceptible to removal than, for example, clay, but I'm far from as knowledgeable on this topic as you are so I'm curious.

 

[buckeye05]

does the composition of the ground have an impact? I would imagine (purely conjecture) that soft soil is lighter and more susceptible to removal than, for example, clay, but I'm far from as knowledgeable on this topic as you are so I'm curious.

According to NWS surveyors I have spoken to, soil type and ground composition can make certain areas more or less vulnerable to scouring, but I can't tell you which specific types are associated with what. I would imagine a loose, non-compact soil may result in that trench digging phenomenon we occasionally see. Another tricky thing is loam soils you see in Texas and Oklahoma. That sometimes produces what I call "pseudo ground scouring, where the fine powdery reddish loam soil is picked up and plastered against the grass, without any actual removal of grass or surface vegetation. This can create a streak of discoloration that looks like scouring from afar, but isn't when inspected up close. This happened in several areas along the Bridge Creek 1999 path, but so did some very legit scouring where only bare soil was left. That's why it's important to have a close-up view and see how much vegetation is actually removed, and why aerial photos usually won't tell you much when it comes to scouring.

 

[notsoencrypted]

Then there's also the issue of soil in crop fields, which is regularly worked (even if just annually) which makes it less compacted, vs pasture or prairie, which may have very sturdy rooted plants and grasses. And those are different than turf grass areas, which still have more compacting and roots than a field but less structural support from roots than a prairie.

 

[buckeye05]

Then there's also the issue of soil in crop fields, which is regularly worked (even if just annually) which makes it less compacted, vs pasture or prairie, which may have very sturdy rooted plants and grasses. And those are different than turf grass areas, which still have more compacting and roots than a field but less structural support from roots than a prairie.

You are 100% correct. People on twitter/youtube always flip out and say "omg look at the violent scouring!!!!" any time a path of discoloration is visible in a farm field. I used to take the time to point out that it's not like grass scouring because it's a farm field, which is full of already exposed soil that has been tilled and can splatter against the crops, and has widely spaced vegetation (like the photo at the top of this page). But people don't want hear that, and like hyping up anything that can conceivably be called ground scouring, so I've stopped even bothering.

 

[cincywx]

You are 100% correct. People on twitter/youtube always flip out and say "omg look at the violent scouring!!!!" any time a path of discoloration is visible in a farm field. I used to take the time to point out that it's not like grass scouring because it's a farm field, which is full of already exposed soil that has been tilled and can splatter against the crops, and has widely spaced vegetation (like the photo at the top of this page). But people don't want hear that, and like hyping up anything that can conceivably be called ground scouring, so I've stopped even bothering.

I stopped putting a ton of stock into reports of ground scouring a few years ago after noticing the bolded as well. There will certainly be eye-popping ground scouring again at some point, but in general, it seems that more often than not, hyperbole & misunderstanding (with regard to ground scouring) come together to birth the idea that a given tornado was much stronger than it truly was.

 

[Tempestas Tonitrua]

There hs only been one photo out of that area so far...why aren't more coming in?

Probably because it’s so rural or the damage isn’t anything crazy.

This isn’t scientific by any means and completely anecdotal, but usually after high end events the pictures start flowing in fast (Mayfield, Rolling Fork, Moore 2013 with it being called Joplin-esque within the first two hours).

 

[atrainguy]

I stopped putting a ton of stock into reports of ground scouring a few years ago after noticing the bolded as well. There will certainly be eye-popping ground scouring again at some point, but in general, it seems that more often than not, hyperbole & misunderstanding (with regard to ground scouring) come together to birth the idea that a given tornado was much stronger than it truly was.

A bit off topic, but that same thought about untrustworthy hyperbole has crossed my mind about tornadoes from the pre Fujita scale days. How many that are considered probable F5s due to extreme damage descriptions like farms "disappearing" and extreme tree damage and ground scouring were actually just (E)F3s or (E)F4s leveling or sweeping away old poorly constructed houses and barns, and the overall descriptions from witnesses were exaggerated. Heck, listen to experienced storm chasers initially claiming towns are gone/disappeared, when it's "only" EF3 damage. Even notable death tolls - are they always indicative of high end tornadoes, or were they a result of there being no tornado warnings and everybody being caught by surprise by a strong F3? Obviously there are some that definitely were definitely deserving of their ratings and reputations from legit evidence to back it up, like New Richmond and the Tri State, but in regards to other more obscure tornadoes, or ones that don't have much if any photographs of their damage due to a lack of cell phones and cameras being more rare.

 

[tornado examiner]

Or it's the case where the Hollister tornado was actually not very strong at all at ground level..aerial footage shows minor grass blowing and somewhat denuded trees at worst...some minor roof damage here and there...also a silo bent up a bit...

 

[Maxis_s]

Or it's the case where the Hollister tornado was actually not very strong at all at ground level..aerial footage shows minor grass blowing and somewhat denuded trees at worst...some minor roof damage here and there...also a silo bent up a bit...

I doubt they found the main damage path. There's no way that thing was weak.

 

[Tomcats Forever!]

Well, it was only about 10 miles from the radar, we keep seeing that adding a *lot* to the velocities.

 

[joshoctober16]

A bit off topic, but that same thought about untrustworthy hyperbole has crossed my mind about tornadoes from the pre Fujita scale days. How many that are considered probable F5s due to extreme damage descriptions like farms "disappearing" and extreme tree damage and ground scouring were actually just (E)F3s or (E)F4s leveling or sweeping away old poorly constructed houses and barns, and the overall descriptions from witnesses were exaggerated. Heck, listen to experienced storm chasers initially claiming towns are gone/disappeared, when it's "only" EF3 damage. Even notable death tolls - are they always indicative of high end tornadoes, or were they a result of there being no tornado warnings and everybody being caught by surprise by a strong F3? Obviously there are some that definitely were definitely deserving of their ratings and reputations from legit evidence to back it up, like New Richmond and the Tri State, but in regards to other more obscure tornadoes, or ones that don't have much if any photographs of their damage due to a lack of cell phones and cameras being more rare.

i think the F scale rated tornadoes are best fit like this.
F0 = EF0: 65-85 mph
F1 = EF1: 86-109 mph
F2 = EF1+: 110-135 mph
F3 = EF3: 136-149 mph
F4 = EF3+: 150-167 mph
F5 = EF4: 168-199 mph
F5+ (270+ mph rating or almost rated F6) = 200+ mph

if you think of it like that it seems to make all the weird issues go away
in a quick way F0-F2 are pretty much the same , but the EF3 rated tornadoes of today would be rated F3 or F4.
the F5 are todays EF4, and the high end F5 events are todays EF5

the only for sure thing i for sure know that is true is all 200 mph EF4 tornadoes would be F5 on the old scale. im still unsure if that's were F5 are meant to truly start or not.

 

[atrainguy]

Enhanced for today has grown, especially southward into central Texas. Again, only 5% tornado risk, but SPC has this in their discussion:

"Supercells capable of very large hail, damaging winds, and tornadoes are possible along this corridor through the early evening. There is a chance of a strong tornado or two, but confidence in position is not high enough to increase tornado probabilities at this time."

SPC Day 1 Outlook

Severe weather, tornado, thunderstorm, fire weather, storm report, tornado watch, severe thunderstorm watch, mesoscale discussion, convective outlook products from the Storm Prediction Center.

www.spc.noaa.gov

 

[atrainguy]

 

[joshoctober16]

landspout tornado on the ground but no tornado warning? , i herd a radio say there are 3 on the ground

 

[atrainguy]

First warning of the day.

 

[atrainguy]

 

[atrainguy]