Quincy

Big ice makers today 

One observation I’ve noted about the NW Texas tornado watch is that low-level hodographs are still relatively small. 0-1km SRH via 21z mesoanalysis is below 100 m2/s2 near and immediately ahead of the arc of cells. 

It looks like a lead, subtle perturbation in the warm air advection regime sets off a mess of convection by midday across central/eastern Texas into eastern Oklahoma. 

While the HRRR lacks CI away from the triple point area in NW OK (which gets undercut by a cold front), the 3km NAM and WRF/ARW members are much more active in SW OK.

Looking at the HRRR forecast soundings, I’m not quite sure why it doesn’t initiate convection there. It shows virtually no CIN, temperatures reaching convT and large CAPE profiles. I’m guessing it has to do with overzealous mixing and/or the tendency for HRRR to be too late with CI.

The setup does seem a bit off. Maybe a touch too slow as some have mentioned, at least in comparison to 4/22/20. The HRRR is furthest north, while the 3km NAM places the triple point the farthest southwest.

At this juncture, I’d say Texas is mostly out of any dryline action, with the only possible exception being if the low tracks farther south. If the 3km were onto a trend, maybe you see storms initiate in far NW Texas. 

The surging cold front looks like it will undercut storms closer to the surface low in western OK. 

We may have to wait until morning to really get a better idea of specifics, but I wouldn’t write this setup off yet. 

It’s definitely complicated. Reminds me of a tamer version of 5/9/16. Recall that SPC and some others (like me) thought the warm sector looked better. The dryline went nuts in what was almost a colossal bust on my end. Also seeing some shades of Springer as well.

The new HRRR has a late CI bias, but other models also show limited QPF/CI signals. I actually like that. If you do get an isolated storm or two, then they have a chance to go bonkers. Forecast soundings ahead of the dryline show classic thermodynamic profiles and while hodographs may not be extremely large, I’d gather they’d support a photogenic supercell. 

CI near the triple point seems to have the best model support, but that might get undercut by the cold front. 

I pulled some warm sector soundings and low-level lapse rates look rather anemic.

The dryline south of the Red River seems like the biggest wild card that could go boom or bust in a big way. 

At the very least, the Plains is waking up!

The trend appears to be feeding better instability and moisture up to I-40 now. It’s in weenie NAM land, but the fact that the 12km shows very sparse convection with minimal CIN in central/southern Oklahoma toward 00z, catches your attention.

Without getting into specifics, as the forecast will evolve, it definitely bears watching from roughly the DFW - OKC area. 

Could see isolated convection farther south as well, as we’ve seen a few times this month. 

There’s definitely a noteworthy signal, but this is well into the medium range, so let’s see how it evolves in the coming days...

Just now, stormdragonwx said:

I hear ya man. I was right up the road from you. Watched that one promising storm fall apart over Florence. Looks like we are done around here as the other rain showers further south and west look to be struggling.

It looked interesting for a short time. Logistically, I couldn’t go too far east or southeast since I have obligations in Oklahoma tomorrow morning. At least I was able to bail before it got too late in the day.

Stas is a beast. He claims he sucks at chasing Dixie, but his results say otherwise. 

1 hour ago, Quincy said:

I’m at a clearing near Vina, AL on a hill. View is partially occurred and will be repositioning to the NE momentarily... Can sort of see a grungy wall cloud to the west. 

Typical post-2016 Dixie chase for me. Bust!

Central Alabama was really the place to be today. Not looking so hot for the southern burbs of Birmingham again...

I’m at a clearing near Vina, AL on a hill. View is partially occurred and will be repositioning to the NE momentarily... Can sort of see a grungy wall cloud to the west. 

1 minute ago, jojo762 said:

Cell north of Smithville, MS is going to need a warning probably...

I’m on the AL side heading up to get into position for this storm. Will pass on if I see anything interesting. 

We’re kind of beyond NAM range, but FWIW, it pops supercells all over the place from northern MS into TN and KY over the next few hours...

1 minute ago, MattPetrulli said:

That cell and the cell to its south both have pretty big potential imo

The I-20 corridor looks like it has potential for several more hours. The return flow is pumping unstable air back north. Hopefully more storms don’t take a beeline toward Birmingham...

Just now, ALweather said:

That seems to be the trend lately. Is there a reason for this? Have they changed their parameters for issuing one or are they just more trigger happy than they once were?

I also wonder how closely they use HREF probabilities as a guideline. They usually don’t deviate far from that. That popped a small tornado driven high risk at 12z. 

2 minutes ago, nwohweather said:

Meh I'm not totally sold here. SRH is not what it should be for this

Surface winds are more backed up here, but low level flow is rather weak. I’m actually in NE MS “chasing” now, near the AL border. More like making a decision soon if I’m going to bail back to Oklahoma. 

11 minutes ago, CoastalWx said:

The directional shear didn't seem as impressive to me as some of the bigger outbreaks. But this one has some steep mid level lapse rates and strong wind velocities to maybe offset the lack of directional shear.

Outbreaks are very difficult to predict in terms of how many SUP cells or intense tors. One or two ingredients can be altered slightly which is the difference between St Patty's Day 2021 and April 2011. 

It’s still a bit early, but I agree with this, especially for the western part of the risk area, closer to the MS River. Sure, we have large CAPE and near-record lapse rates, but the wind field there is just about unidirectional now. 

I think that getting big CAPE and large hodographs in the Southeast is exceedingly rare. The writing was on the wall when midday SRH maps looked relatively modest, west of the MS/AL border.

Farther east has been a different story. CAMs remain aggressive with the zone of messy storm modes breaking into semi-discrete storms. It could still happen, but we’ll see. The air mass is recovering over central MS, but low level shear would need to improve. Of course you had that one long track supercell go largely unimpeded on the SE fringe of convection.   

50 knot low level jet core advecting across southeastern Louisiana. Low level instability increasing across Mississippi/western Alabama. 7-8 C/km mid level lapse rates in place. Very little convective inhibition left across Mississippi. Things are about to get real. 

I wouldn’t write off the southeastern half of Mississippi yet. There has been a slight southeast trend with recent HRRR runs. Note that the axis of a boundary exists from roughly Jackson-Columbus-Huntsville with ongoing and soon to be new convection along and southeast of this boundary. 

One thing to note is the ongoing conveyor belt across central/eastern Mississippi. The most ideal parameter space is progged to develop along and just southeast of this zone by midday/early afternoon. The HRRR has trended just a tick SE, zeroing in on central/eastern Mississippi into central Alabama. You can obviously have tornadoes elsewhere, but you can envision a scenario with several long track, strong tornadic supercells racing across this area. 

Initial look at a couple 12z soundings. JAN needs some boundary layer recovery, but that won’t take long with this setup. LIX is already quite unstable. Look at that CAPE...

One thing I have noticed from early morning data is that low-level lapse rates are not very favorable yet. Mostly <6 C/km. That means it will probably be a few hours at least until action really gets going. Probably midday? Possibly late morning. 

CIPS analogs deep into weenie territory now, but the pre-frontal signal for long track tornadoes in the MS/AL vicinity has been very consistent. It also aligns closely to a blend of CAMs. I won’t mention the top analog, but I will say the forecast LLJ tomorrow at 00z is stronger than any of the 15 analogs.

Shawn Milrad tipped us off to the EML showing up via 00z sounding from LZK/Little Rock...

The 00z 3km NAM is either scary af, clueless or both. I cherry picked some soundings with 700-500mb lapse rates over 9 C/km with Tds in the lower 70s. Even area averaged soundings show lapse rates around 8 C/km with a small capping inversion. Important note is that low level lapse rates in this environment are marginal, in some cases <6 C/km.

If the cold bias is correct, you’d have that tiny cap being obliterated. 

Is it overly simplified to say a HRRR/3km NAM blend is one of the scariest scenarios you could fathom? HRRR is messy with widespread convection, while the NAM is just a little bit too cool in the boundary layer, resulting in very little warm sector convective initiation. 

Texas doing the day before the day things...