2026 Mid-Atlantic Severe Storm General Discussion

[SnowenOutThere]

5 minutes ago, George BM said:

Sounding is in.

Experts?

From my 3000 course Atmosphere and Weather the only thing that fully stands out is the slight rightward nudge between 500mb and 300mb. Seems odd that’d prevent a mature thunderhead considering the abundant cape still present. Maybe the other piece is the hodograph which only has unidirectional shear up to sounding point 2? Will page some of our smarter friends to help out @high risk @CAPE @MillvilleWx

[high risk]

1 hour ago, Eskimo Joe said:

Two thoughts come to mind:

1.) These are machine learning/AI-influenced CAMS that don't yet have the "database" of events to properly articulate when these events die off.

2.) As we saw with April 2011 and the 2012 Derecho, mature MCS complexes persist longer than meso guidance if the downstream airmass is sufficiently unstable. However, the lack of an EML or good jet streak generally isn't enough to sustain the storms much past sunset. There is an eight part YouTube video from Rich Thompson (SPC met) speaking a Univ of Oklahoma and he talks about this extensively. I cannot find the YouTube series unfortunately.

          None of these CAMs are AI-based.    This event, like Saturday's, was mostly a burst of wind followed by a mostly narrow band of reflectivity.    I'm guessing that this type of event is tough for a 3 km model to properly resolve.

[high risk]

10 minutes ago, SnowenOutThere said:

From my 3000 course Atmosphere and Weather the only thing that fully stands out is the slight rightward nudge between 500mb and 300mb. Seems odd that’d prevent a mature thunderhead considering the abundant cape still present. Maybe the other piece is the hodograph which only has unidirectional shear up to sounding point 2? Will page some of our smarter friends to help out @high risk @CAPE @MillvilleWx

      It's a fair question, especially given that there is more shear in that profile than I was expecting to see.   The warm layer you mentioned might indeed have been a factor.   I'd also note that the surface dew point doesn't seem to be representative of the moisture in the low levels, so a mixed layer parcel, while still having some CAPE, would not be able to generate as strong of an updraft.  

[vortex95]

31 minutes ago, George BM said:

Sounding is in.

Experts?

As noted in previous posts, odd for temps in the 90s and DPs 70  It acted more like a cool season line of gusty heavy showers.  00z analyzed NAM 1000-500 thk for DCA was 577, so that usually means 50k CB tops easy and lots of LTG.

Peak mid-level lapse rates on the 00z IAD sounding were 7.0 C/km between 700-500 and CAPE at mid-levels was "fat."  That should have lead to solid charge separation in the supercooled water level for lots of LTG.  K-index 36, so not dry aloft.  Sfc T-Td spreads around 25 so not too dry at low levels.  Yet things were very outflow-ish.

Storm cores should have been "meatier" for the lack of a better term!

The thing that stands out in the sounding is the lack of solid deep layer shear, so that likely precluded stronger coherent cells or a more solid/thicker SQLN.

[high risk]

19 minutes ago, vortex95 said:

The thing that stands out in the sounding is the lack of solid deep layer shear, so that likely precluded stronger coherent cells or a more solid/thicker SQLN.

                I think you're on the right track here, but the mid-level flow was better than modeled.  I suspect that the paltry winds at the upper levels limited the strength of the updraft.

[George BM]

11 minutes ago, high risk said:

                I think you're on the right track here, but the mid-level flow was better than modeled.  I suspect that the paltry winds at the upper levels limited the strength of the updraft.

That combined w/ that warmer ~400mb layer preventing the updrafts from really getting up towards the EL would be my non-redtag hypothesis. 

[SnowenOutThere]

46 minutes ago, high risk said:

      It's a fair question, especially given that there is more shear in that profile than I was expecting to see.   The warm layer you mentioned might indeed have been a factor.   I'd also note that the surface dew point doesn't seem to be representative of the moisture in the low levels, so a mixed layer parcel, while still having some CAPE, would not be able to generate as strong of an updraft.  

34 minutes ago, vortex95 said:

As noted in previous posts, odd for temps in the 90s and DPs 70  It acted more like a cool season line of gusty heavy showers.  00z analyzed NAM 1000-500 thk for DCA was 577, so that usually means 50k CB tops easy and lots of LTG.

Peak mid-level lapse rates on the 00z IAD sounding were 7.0 C/km between 700-500 and CAPE at mid-levels was "fat."  That should have lead to solid charge separation in the supercooled water level for lots of LTG.  K-index 36, so not dry aloft.  Sfc T-Td spreads around 25 so not too dry at low levels.  Yet things were very outflow-ish.

Storm cores should have been "meatier" for the lack of a better term!

The thing that stands out in the sounding is the lack of solid deep layer shear, so that likely precluded stronger coherent cells or a more solid/thicker SQLN.

11 minutes ago, high risk said:

                I think you're on the right track here, but the mid-level flow was better than modeled.  I suspect that the paltry winds at the upper levels limited the strength of the updraft.

1 minute ago, George BM said:

That combined w/ that warmer ~400mb layer preventing the updrafts from really getting up towards the EL would be my non-redtag hypothesis. 

Thanks to everyone for responding! Adding to this discussion with the echo tops and visible sat estimated from the KIAD radar. Seems to support the general idea of a low topped environment. Can see that one cell southwest of DC trying to reach upward, but the real visible edge of the storms as the low level outflow induced shelf clouds. What an interesting storm system; had low topped storms in a high CAPE environment and despite that had significant wind with it. Always interests me why a certain storm is a particular way. Also helped show me CAPE isn't everything I thought it is. 

[jewell2188]

How is tomorrow looking? More of a trigger versus today?

[AlexD1990]

Never got a thing over here, after being blasted last night with a one off.

[CAPE]

52 minutes ago, SnowenOutThere said:

Thanks to everyone for responding! Adding to this discussion with the echo tops and visible sat estimated from the KIAD radar. Seems to support the general idea of a low topped environment. Can see that one cell southwest of DC trying to reach upward, but the real visible edge of the storms as the low level outflow induced shelf clouds. What an interesting storm system; had low topped storms in a high CAPE environment and despite that had significant wind with it. Always interests me why a certain storm is a particular way. Also helped show me CAPE isn't everything I thought it is. 

 

[CAPE]

7 minutes ago, AlexD1990 said:

Never got a thing over here, after being blasted last night with a one off.

The broken line died just to the west of me, but had a nice outflow with some wind to dry things up a bit more.

[vortex95]

1 hour ago, high risk said:

                I think you're on the right track here, but the mid-level flow was better than modeled.  I suspect that the paltry winds at the upper levels limited the strength of the updraft.

Thanks.  0-6 km shear was only 15 kt at IAD, well below the threshold for marginal supercells (30-35 kt), so storm lacked mid-level mesos.  All you need is a half-decent meso at mid-levels, and that makes storms *so* much "better."  Even if no severe wx, the LTG and rainfall ramps up!

0-8 km shear was even weaker at 14 kt.  And look at hodograph, it is a chaotic mess!

Tons of CAPE only takes you so far.  If the shear is lousy, it's hard to sustain discrete, long-lived cells.  I'd take 1500 CAPE and 0-6 kt shear 40-45 kt anytime over 3500 CAPE and 0-6 shear 15-20 kt!

The presence of good wind shear also prevents storms from gusting out too easily.  The updraft and downdraft couplets in the storms are separated better in a higher-sheared environment.

I realize some already know this, but this is a very important point when it comes to mesocyclones.  The presence of  mesocyclone just at mid-levels (low-levels can be nothing) greatly enhances the potential updraft strength of a tstm.  It can double the updraft strength from buoyancy (CAPE) alone though dynamic pressure perturbations, so that's why supercells have such intense updrafts.

1500-2000 CAPE may not sound like much, but if the shear is ideal, holy cow.  For instance, the April 1965 Palm Sunday Outbreak in the OH Valley, CAPE was 1500-2000, and the 0-6 kt shear was about as high as I have ever seen it for an outbreak.  It was 100-110 kt!  That's crazy, and you had a lot of intense, long-tracked tors.
 

[vortex95]

1 hour ago, George BM said:

That combined w/ that warmer ~400mb layer preventing the updrafts from really getting up towards the EL would be my non-redtag hypothesis. 

Yes, the little details count when it comes to svr wx events.  *One* thing off, and it can be the difference between several tors or none, or several intense, long-tracked tors or a bunch of weak, short-lived ones.  For instance, sfc dew points are a few degrees lower than fcst.  This raises the LFC, and lessens 0-3 km CAPE, which are key for tors.

How many times does it look good "on paper" for big svr wx, and it fails.  SCP and SIGTOR are high, and it's a major disappointment and under-performs.  SCP and SIGTOR can't account for everything going on, they account for just some.  They can't be treated in a vacuum!

Of course, the door can swing the other way.  How about June 5, 2024?  That was a surprise!  Yes, SPC had 2% tor risk, but it did not stand out as "big" for tor event in this area.  It was not synopitcally-evident.  And we got what, 13 tors?  And they were not all just brief spin ups!