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Severe Weather Threat 4/27-4/28

I really haven't been too active lately on this forum, but Broyles did get back to me after a question I asked regarding faster jets and morning convection and he actually asked my thoughts on the underperformance. He mentioned a meridional 500 mb jet, compared to latiudinal, which I believe @ColdFront had spotted this in earlier models run noting the trajectory of the 500 mb jet.

I decided to analyse the day and found the presumably main culprit: 700 mb temperatures stunting prefrontal convection, and also stunting the mainly volatile parameter space in S MO. And when 700 mb temps cooled, this is where we seen our tornado in Arkansas but these discrete cells were in a unfavourable orientation after lining out, so nothing really happened after. @N0mz has already pointed this out, but this was the main thing I really found limited this event combined with a misplaced jet.

I'm hoping my insights right here. These high end ceiling events underperforming aids us a lot.
 
WeathermanLeprechaun said:
I really haven't been too active lately on this forum, but Broyles did get back to me after a question I asked regarding faster jets and morning convection and he actually asked my thoughts on the underperformance. He mentioned a meridional 500 mb jet, compared to latiudinal, which I believe @ColdFront had spotted this in earlier models run noting the trajectory of the 500 mb jet.

I decided to analyse the day and found the presumably main culprit: 700 mb temperatures stunting prefrontal convection, and also stunting the mainly volatile parameter space in S MO. And when 700 mb temps cooled, this is where we seen our tornado in Arkansas but these discrete cells were in a unfavourable orientation after lining out, so nothing really happened after. @N0mz has already pointed this out, but this was the main thing I really found limited this event combined with a misplaced jet.

I'm hoping my insights right here. These high end ceiling events underperforming aids us a lot.
Click to expand...
This is a great callout @WeathermanLeprechaun.

I didn’t realize how much 700 mb temps mattered (it makes much more sense now because that helps lift and erode the EML) until I saw Broyles discussing it on Trey’s channel.

Just a side note on this specific subject. I’ve been working on a personal research project for the 1974 super outbreak (I don’t plan to publicly release it but once it’s finished I’d be happy to share it with anyone who asks). I reached out to a few of the authors of the “Revisiting the 1974 Super Outbreak” paper with questions specifically around the formation of convective band 2, which was responsible for the vast majority of violent tornados that day. They noted 700MB cooling played a big role in its development, but the exact cause of the cooling was unknown. One of the authors theorized it could have been air parcels in the mid level jet that bled over into the outbreak space as they exited the jet. He also noted distinct 700 MB cooling is present in a lot of higher end events.
 
ColdFront said:
I really think we are going to have big storm mode issues here, NAM’s gross linear bias notwithstanding. I’m not saying we won’t have embedded supercells or a small window for some discrete supercells, but that jet is just a firehose of forcing right over that area. While the trough is negatively tilted, I’d still like to see more zonal flow geometry instead of that sharp-meridional flow right into the warm sector Monday.

It’s a freaking puzzle trying to figure out storm mode at this range though.

edit: Not downplaying this threat at all btw. I’m more speaking of factors that would cause this event not to reach an upper-end ceiling
Click to expand...

It just so happens @ColdFront calling out the issue of the event is located on the very first page of this new thread lol. One of the first comments.
 
Gotta hand it to him, I really disagreed with him on that point. The flow did not look all that meridional to me on the model solutions at the time. I thought some days which produced big outbreaks (including 3/31/23) had a considerably greater meridional (southerly) component to the flow in the left exit region where it overspread the warm sector.

In fact, I've seen some troughs that are so negatively tilted the 500mb flow is actually out of the SSE! In that case, you can sometimes get tornadic supercells that move due north or even NNW!
 
Grand Poo Bah said:
It just so happens @ColdFront calling out the issue of the event is located on the very first page of this new thread lol. One of the first comments.
Click to expand...

CheeselandSkies said:
Gotta hand it to him, I really disagreed with him on that point. The flow did not look all that meridional to me on the model solutions at the time. I thought some days which produced big outbreaks (including 3/31/23) had a considerably greater meridional (southerly) component to the flow in the left exit region where it overspread the warm sector.

In fact, I've seen some troughs that are so negatively tilted the 500mb flow is actually out of the SSE! In that case, you can sometimes get tornadic supercells that move due north or even NNW!
Click to expand...

A blind squirrel finds a nut every once in a while.

No, on a serious note, the geometry did look weird to me. However, I wasn’t really able to properly articulate the “why” without the aid of screenshots, which just lead to overall confusion at what exactly I meant. I do think capping and 700 mb temps had a slightly higher impact than the trough and its geometry, but the trough certainly didn’t help things as sometimes jet placement can help erode a warm sector cap through ascent.

Imagine if the cap eroded and we had open warm sector convection. That post I made would’ve aged really bad haha.
 
Grand Poo Bah said:
Crazy it's still not back. Admins have been MIA for over a week since the last update. Getting ridiculous.
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Yeah, I would agree at this point. It also seems like we just have one technical admin that can actually update the site. I would concur with something @Central Ohio Wx said, I don’t think I’ve ever seen a forum just technically decay like this for this long.
 
ColdFront said:
This is a great callout @WeathermanLeprechaun.

I didn’t realize how much 700 mb temps mattered (it makes much more sense now because that helps lift and erode the EML) until I saw Broyles discussing it on Trey’s channel.

Just a side note on this specific subject. I’ve been working on a personal research project for the 1974 super outbreak (I don’t plan to publicly release it but once it’s finished I’d be happy to share it with anyone who asks). I reached out to a few of the authors of the “Revisiting the 1974 Super Outbreak” paper with questions specifically around the formation of convective band 2, which was responsible for the vast majority of violent tornados that day. They noted 700MB cooling played a big role in its development, but the exact cause of the cooling was unknown. One of the authors theorized it could have been air parcels in the mid level jet that bled over into the outbreak space as they exited the jet. He also noted distinct 700 MB cooling is present in a lot of higher end events.
Click to expand...
@N0mz was the man of work for this, i just decided to see if he was spot on and he was. We weren't supposed to have such a stout warm nose at play, and as a result, it just added salt to the wound on a already subtly forced day. I haven't got a response from Broyles just yet but I am thoroughly curious to see what he says about this. I do think this was the main culprit at hand.
 
Stats from April 28th thru this morning:
Lightning (data from Tempest WX Station):
April 28th: 2,904
April 29th: 811
April 30th: 23
3-Day Lightning Total: 3,738

Total 3-Day Rainfall: 6.20 inches

Ending April with a rainfall total of 7.63 inches. Rainfall for year got boosted from 13.87 (January thru March) to now 21.50

For those using Tempest Weather Stations or any weather station, I would still have a manual rain gauge at hand. This past event is where I was very thankful I still had a manual gauge to go out to and measure myself. The tempest just recorded 1.49 inches on April 28th then 0.67 inches on April 29th. Why would that be? Here's why. Because if you have a storm that is slow moving/trains over same area producing very heavy rainfall, the Tempest can't keep up.
 
CheeselandSkies said:
Gotta hand it to him, I really disagreed with him on that point. The flow did not look all that meridional to me on the model solutions at the time. I thought some days which produced big outbreaks (including 3/31/23) had a considerably greater meridional (southerly) component to the flow in the left exit region where it overspread the warm sector.

In fact, I've seen some troughs that are so negatively tilted the 500mb flow is actually out of the SSE! In that case, you can sometimes get tornadic supercells that move due north or even NNW!
Click to expand...
I believe trey mentioned meridional flow as a potential failure mode of 3/16. I haven't really investigated that one, though, it had me a little too depressed to figure it out :p
 
WeathermanLeprechaun said:
For the record, i plan to calculate most significant tornado events and their 500 mb jet translation speed. I think it'd be a interesting project and when I'm done with it, i will share it!
Click to expand...
Maybe reach out to Grace Cohen. She created some of the tools for the omega project that automatically tracked 500mb translation speed. She's on Twitter and probably reachable at other places.

https://x.com/GraceCWeather
 
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