2021 Mid-Atlantic Severe Weather - General Discussion

[high risk]

I don't understand this event at all.     The parameters don't seem to support what seems to be a fairly impressive severe event (albeit along a narrow corridor) this evening.

[George BM]

1 minute ago, high risk said:

I don't understand this event at all.     The parameters don't seem to support what seems to be a fairly impressive severe event (albeit along a narrow corridor) this evening.

I had noticed early this evening (6-8pm) that the dewpoint temps had risen to the low/mid 70's yielding 1500+ J/kg SBCAPE. Okay, I thought, that little bit of convection in the mountains may intensify into heavy downpours w/ occasional lightning and gusty(non-severe) winds given the 40kt EBWD. But legitimately severe winds with a potential tornado? Nope I certainly didn't anticipate the convection getting THIS intense.

[SmokeEater]

Supposedly this was the tornado in Milford, DE earlier.

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[LP08]

 

[Maestrobjwa]

29 minutes ago, SmokeEater said:

Supposedly this was the tornado in Milford, DE earlier.

Sent from my SM-G973U using Tapatalk
 

Are you kidding? Looks like in the middle of Kansas or something!

[NorthArlington101]

[WxWatcher007]

1 hour ago, GATECH said:

When was the last time we saw a tor warn for the district….

 

[NorthArlington101]

 

[jac_not_in_dc]

Oh sure, it goes right over my house and I'm 2,000 miles away.

 

 

[NorthArlington101]

12 hours ago, high risk said:

I don't understand this event at all.     The parameters don't seem to support what seems to be a fairly impressive severe event (albeit along a narrow corridor) this evening.

I realize you said you don't understand it, but I'd love someone (smarter than me) to do a breakdown on this storm and how this came together. I was casually watching the radar, and it looked like no big deal till it was about five minutes from impact. This was even the third round of storms! Shocking.

[George BM]

19 minutes ago, NorthArlington101 said:

I realize you said you don't understand it, but I'd love someone (smarter than me) to do a breakdown on this storm and how this came together. I was casually watching the radar, and it looked like no big deal till it was about five minutes from impact. This was even the third round of storms! Shocking.

Now while most of the time MLCAPE is more representative of the instability in the atmosphere for storms SBCAPE from the 00z IAD sounding yesterday evening was fairly high 1500-2000J/kg (I'm guessing from limited solar radiation through the afternoon following the earlier storms heating up and evaporating water from the surface leading to higher dewpoints near the surface?) compared to MLCAPE. Now I don't know too much about how storms interact with MLCAPE vs. SBCAPE. I'm wondering if the relative high SBCAPE was a big factor to the intensity of the post-dusk intensity of the storms... especially when combined with relatively fast flow aloft in the mid-levels of the atmosphere as seen below. I too would love to learn about that. Perhaps @high risk @csnavywx know more about storm behavior wrt ML and SB cape?

 

[WxWatcher007]

 

[mappy]

Ef1 in Arlington 

 

[vastateofmind]

23 hours ago, mappy said:

Ef1 in Arlington 

 

So, we were texting our youngest son who lives in Arlington about four blocks south of that area when that storm hit. He asked if OUR power went out (in SE FfxCo) and I said no....but that was kind of a warning flag that Arlington was getting SPANKED at the time, and it sure as hell looked like that on radar at the time, based on my limited interpretation, and what Ian and a couple others saw and shared online at the time. Pretty impressive dynamics, for something that wasn't necessarily called for ahead of time.

[high risk]

On 7/2/2021 at 10:48 AM, George BM said:

Now while most of the time MLCAPE is more representative of the instability in the atmosphere for storms SBCAPE from the 00z IAD sounding yesterday evening was fairly high 1500-2000J/kg (I'm guessing from limited solar radiation through the afternoon following the earlier storms heating up and evaporating water from the surface leading to higher dewpoints near the surface?) compared to MLCAPE. Now I don't know too much about how storms interact with MLCAPE vs. SBCAPE. I'm wondering if the relative high SBCAPE was a big factor to the intensity of the post-dusk intensity of the storms... especially when combined with relatively fast flow aloft in the mid-levels of the atmosphere as seen below. I too would love to learn about that. Perhaps @high risk @csnavywx know more about storm behavior wrt ML and SB cape?

 

         Thanks for continuing the discussion and for posting the sounding.   In the big picture for SB vs MLCAPE, MLCAPE seems to be more representative of the air feeding into a storm if the environmental is deeply mixed.      Once you go into the evening, and decoupling begins, SBCAPE is arguably more representative, although there are certainly exceptions.

         In the IAD sounding above,  it's certainly not well-mixed, especially with the low-level moisture profile, so perhaps SBCAPE is a better representation, although the higher moisture values drop off quickly above the ground.     That moisture profile makes it pretty easy to see why MLCAPE is so much lower....    If, however, a parcel was surface-based, it did have some instability to work with, and there is some decent 0-3 km CAPE to help achieve stronger upward acceleration.      Given the earlier rounds of storms, I would have expected the temperature profile to be more moist adiabatic, but it actually had some decent low-level lapse rates.

         All of that said, I don't understand getting a sustained low-level mesocyclone out of this environment.     Deep layer shear was good, and you can make a case for some rotation in the storm.    But getting that rotation in the low-levels is an entirely different ballgame, and the low-level shear was meh - confirmed by the unimpressive values of 0-1 and 0-3 km helicity values.       Perhaps there was a leftover boundary oriented ESE  to WNW through DC, and the storm rode along it, greatly improving the helicity (there was certainly some existing directional shear in the lowest 0.5 km or so).   The low LCLs would have greatly improved the chances of getting something to the ground, and that's confirmed by the videos of the storm hugging the ground.     The fact that this cell was the only one in the area after dark that went severe argues for some localized enhancement of the environment in that Reston-DC-Bowie corridor.

         Still, this sounding has sneaky severe potential, but it certainly doesn't scream 'tornado!'.

 

 

[KAOS]

[Stormfly]

What a weird TSW.

[KAOS]

On 7/6/2021 at 3:19 PM, Stormfly said:

What a weird TSW.

Agreed

[KAOS]

BULLETIN - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Warning National Weather Service Baltimore MD/Washington DC 409 PM EDT Wed Jul 7 2021 The National Weather Service in Sterling Virginia has issued a * Severe Thunderstorm Warning for... Baltimore City in northern Maryland... North central Anne Arundel County in central Maryland... Southeastern Baltimore County in northern Maryland... * Until 445 PM EDT. * At 408 PM EDT, a severe thunderstorm was located over Towson, or near Baltimore, moving northeast at 15 mph. HAZARD...60 mph wind gusts and quarter size hail. SOURCE...Radar indicated. IMPACT...Damaging winds will cause some trees and large branches to fall. This could injure those outdoors, as well as damage homes and vehicles. Roadways may become blocked by downed trees. Localized power outages are possible. Unsecured light objects may become projectiles. * Locations impacted include... Baltimore, Pikesville, Middle River, Cockeysville, Sparrows Point, Back River, Glen Burnie, Dundalk, Towson, Catonsville, Essex, Woodlawn, Parkville, Carney, Milford Mill, Perry Hall, Lochearn, Arbutus, Rosedale and Ferndale. PRECAUTIONARY/PREPAREDNESS ACTIONS... For your protection move to an interior room on the lowest floor of a building. && LAT...LON 3947 7640 3939 7636 3940 7635 3938 7631 3922 7647 3918 7670 3920 7671 3922 7670 3923 7672 3932 7677 3953 7652 TIME...MOT...LOC 2008Z 204DEG 12KT 3935 7663 HAIL...1.00IN WIND...60MPH

[yoda]

@high risk @Kmlwx

SPC has nothing on their radar for tomorrow looking at the new Day 2 for our region... but morning LWX AFD seems to suggest otherwise on Friday

[Quote]

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Any impacts from Elsa should be quickly winding down as we continue
into the early morning hours Friday as the storm races into New
England territory. Expect Friday to be somewhat of a mixed bag as
guidance is split on solutions in terms of remnant showers and total
cloud cover. The consensus is that Friday morning looks to remain
mostly dry, aside from the chance for a few hit-or-miss showers
across the mountains. Conditions will remain humid however with dew
points in the 70s. Friday afternoon looks potentially
concerning as the front approaches from the west. The combination of
1000-1500 J/Kg CAPE, 30-40kt 0-6Km shear, and strong forcing
mechanism would yield the potential for developing thunderstorms,
some of which may be severe in nature. Storm severity will be highly
dependent on cloud cover as if clouds hold strong throughout much of
the morning and early afternoon hours, could limit instability.
However, expect some subsidence to counteract this as Elsa continues
to track northeastward.

[/quote]

[high risk]

11 hours ago, yoda said:

@high risk @Kmlwx

SPC has nothing on their radar for tomorrow looking at the new Day 2 for our region... but morning LWX AFD seems to suggest otherwise on Friday

[Quote]

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Any impacts from Elsa should be quickly winding down as we continue
into the early morning hours Friday as the storm races into New
England territory. Expect Friday to be somewhat of a mixed bag as
guidance is split on solutions in terms of remnant showers and total
cloud cover. The consensus is that Friday morning looks to remain
mostly dry, aside from the chance for a few hit-or-miss showers
across the mountains. Conditions will remain humid however with dew
points in the 70s. Friday afternoon looks potentially
concerning as the front approaches from the west. The combination of
1000-1500 J/Kg CAPE, 30-40kt 0-6Km shear, and strong forcing
mechanism would yield the potential for developing thunderstorms,
some of which may be severe in nature. Storm severity will be highly
dependent on cloud cover as if clouds hold strong throughout much of
the morning and early afternoon hours, could limit instability.
However, expect some subsidence to counteract this as Elsa continues
to track northeastward.

[/quote]

       Pretty clear signal for afternoon convection tomorrow, and the CAPE/shear combo currently proved would certainly suggest at least some chance of SVR.

[yoda]

Looks like an active pattern and chance for daily severe starting tomorrow reading the morning AFD 

[MN Transplant]

Marginal for today.  SPC:

 

 ...Eastern States This Afternoon...
   Water vapor loop shows a shortwave trough over WI, with an
   associated cold front extending from western NY/PA into western
   NC/northern GA by this afternoon.  Dewpoints in the 60s to lower 70s
   ahead of the front, combined with pockets of daytime heating and
   modest midlevel cooling will help to destabilize the airmass, and
   lead to scattered afternoon storms along the front.  Flow aloft will
   slowly strengthen today, helping to organize a few of the storms
   into multicell clusters posing a risk of locally damaging wind gusts
   from eastern NY/PA southward across the Carolinas and north GA.  It
   appears at this time that severe storms will be isolated in nature.

[mappy]

3 hours ago, yoda said:

Looks like an active pattern and chance for daily severe starting tomorrow reading the morning AFD 

Starting Sunday, I think. Tomorrow should be pretty awesome. 

[mappy]

Could use some storms tonight, not much in the mood for softball 

[nw baltimore wx]

6 minutes ago, mappy said:

Could use some storms tonight, not much in the mood for softball 

The grind of the regular season.

Could use a storm here after yesterday’s Noonan.

[high risk]

36 minutes ago, mappy said:

Starting Sunday, I think. Tomorrow should be pretty awesome. 

       Definitely.   Somewhat active today and then perhaps active for several days starting Sunday, but Saturday looks like a winner.

 

[mappy]

40 minutes ago, nw baltimore wx said:

The grind of the regular season.

Could use a storm here after yesterday’s Noonan.

Last week was great as we only had one game because of the holiday. That week off between games was amazing. Def just feeling sore, tired and old. lol

11 minutes ago, high risk said:

       Definitely.   Somewhat active today and then perhaps active for several days starting Sunday, but Saturday looks like a winner.

 

I'll take somewhat active today! Heading out on a boat tomorrow

[CAPE]

[Eskimo Joe]

6 minutes ago, CAPE said: