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SNE Convective/Thunder thread


free_man

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What I wrote a few minutes ago for tomorrow

A very interesting setup will unfold across the Northeast tomorrow as a warm front lifts northward bringing back the very hot and humid airmass that was in place Saturday and the advection of an elevated mixed-layer will transport very steep lapse rates into the region along with extreme amounts of instability.

The backdoor cold front which shifted southward through the region Saturday afternoon and evening which was responsible for some severe weather across parts of southern CT/eastern PA and northern NJ has stalled just south of southern New England. This front is expected to retreat back northward as a warm front late Sunday afternoon and evening bringing the chance for a few showers or a t'storm overnight. The warm front is expected to lift back through much of southern New England by Monday morning and stall across central New England. South of the warm front the summer like airmass which encompassed the region on Saturday will return as temperatures will soar into the 80's along with dewpoints around 70F.

Along with the return of this summer time airmass an elevated mixed-layer is working around the top of a strong 700mb ride in place across the central United States. Computer models are all in agreement that this elevated mixed-layer will stay in tact and move into the Northeast and into southern New England. With the elevated mixed-layer comes extremely steep mid-level lapse rates (700-500mb lapse rates should be between 7.5 C/KM and 8.5 C/KM!!) and extreme instability. Computer models are indicating as much as 2500-3500 J/KG of SBcape, 1500-2500 J/KG of MLcape, 2500-3500 J/KG of MUcape, and LI values as low as -6C to -8C. These instability values are quite impressive and you don't see these in New England very often. These values are more common across the Plains where elevated mixed-layers are much more common to occur.

While we will have the extreme instability values in place there are major questions with regards to the amount of wind shear we will have in place tomorrow as well as the source of lift. Unlike cold fronts, warm fronts usually aren't associated with a great deal of lift as their slope isn't as steep as cold fronts. Computer models are also indicating small amounts of CIN (convective inhibition) which could be difficult to overcome without the proper amounts of lift. As far as shear goes there is a little bit of disagreement between computer models with regards to how strong winds aloft will be. One computer model shows about 25-30 knots of deep layer shear developing during the afternoon. While this is rather modest given the extreme levels of instability that will be in place this could be more than sufficient for cell organization. Another computer model only has around 20-25 knots of deep layer shear which is pretty weak and would vastly limit storm organization.

While there are questions with regard to how strong the shear will be computer models are all in agreement that there will be a decent amount of directional shear in place as winds will veer from about the south to southwest at the surface to west to northwesterly aloft in the mid and upper levels of the atmosphere. Despite the lack of speed shear this should yield to some modest helicity values so any cells that develop would have the potential to become supercells and produce very large hail.

With all this said tomorrow is very uncertain as to what will unfold and if we'll even see any t'storm action at all. Questions regarding how strong/if there will be any lift to generate storms and questions to how strong the shear will be make this forecast rather difficult. At this time it appears that central New York, southwestern VT, extreme western MA and northwestern CT would have the best chance to see any storm development but again this all will depend on if we can get strong enough lift. This will have to be closely monitored the next 24 hours.

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In ct? Giving a 30% chance for a tor within 50 miles with less than perfect dynamics is ballsy lol

It's 2 in western CT tomorrow and less than 2 on Tuesday.

I must have missed the 2 on the status update but I went to the website where it lists TOR CON # by state and it's 2 for western CT tomorrow.

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It's 2 in western CT tomorrow and less than 2 on Tuesday.

I must have missed the 2 on the status update but I went to the website where it lists TOR CON # by state and it's 2 for western CT tomorrow.

OK I'm seeing 3 on tuesday. Here's a direct cut and paste... Why the heck can't he just put out a map? He could still make lists, but really this kind of thing is much more understandable when displayed graphically. In any event, the list says 2 for tomorrow and then 3 on Tuesday in western CT. I agree with whoever said this is ballsy, I mean the possibilities are there but I'm not seeing anything that screams tornado outbreak to me.

Monday, May 28

AR northwest - 2

CT west - 2

IL north, central - 3

IN northwest - 3

KS extreme southeast - 2

MA west - 2

MI - 2 to 3

MO north - 3

MO west - 2

NY north - 3

NY south, west - 2

OK south-central, southwest - 3

OK northeast - 2 to 3

PA - 2

TX northwest - 3

TX southwest - 2

VT - 3

WI south, east - 3

other areas - 1 or less

Tuesday, May 29

CT west - 3

DC - 2

KS southwest - 2

MA west - 3

MD - 2

NH - 3

NY northeast - 3

NY rest - 2

OH south, east - 2

OK west - 4

OK central - 3

OK southeast - 2 to 3

PA - 2

KS southwest - 2

TX northwest near Abilene - 2 to 3

VA north - 2

VT - 3

WV - 2

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Wow...I've completely screwed this up like 5 times. That's what I get for not really sleeping the past few days :lol:

Anyways I completely disagree with calling Dr. Forbes ballsy. He's one of, if not THE biggest severe wx expert out there and the TOR Con is his creation and it's been an incredible development. If he's painting a TOR Con of 3 he certainly has a reason for doing so. He will never exaggerate or go over the top.

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Wow...I've completely screwed this up like 5 times. That's what I get for not really sleeping the past few days :lol:

Anyways I completely disagree with calling Dr. Forbes ballsy. He's one of, if not THE biggest severe wx expert out there and the TOR Con is his creation and it's been an incredible development. If he's painting a TOR Con of 3 he certainly has a reason for doing so. He will never exaggerate or go over the top.

I didn't mean any disrespect for Dr. Forbes, I agree he absolutely knows his stuff, I'm just saying that I don't see what he's seeing, so far, I don't think... But I haven't looked at it really deeply and anyway he's the pro, not me, so yeah, you probably would want to place your bets on his predictions, not mine.

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Wow...I've completely screwed this up like 5 times. That's what I get for not really sleeping the past few days :lol:

Anyways I completely disagree with calling Dr. Forbes ballsy. He's one of, if not THE biggest severe wx expert out there and the TOR Con is his creation and it's been an incredible development. If he's painting a TOR Con of 3 he certainly has a reason for doing so. He will never exaggerate or go over the top.

Did it exist before June 1 last year?

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I didn't mean any disrespect for Dr. Forbes, I agree he absolutely knows his stuff, I'm just saying that I don't see what he's seeing, so far, I don't think... But I haven't looked at it really deeply and anyway he's the pro, not me, so yeah, you probably would want to place your bets on his predictions, not mine.

I think alot has to do with the fact that wind fields are favorable for supercells and instability will be high...helicity is forecasted to be around 150 m2s2 which studies have shown is more than adequate in SNE.

Did it exist before June 1 last year?

Yes...if I recall the TOR Con was like 6...might have been 7.

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I think alot has to do with the fact that wind fields are favorable for supercells and instability will be high...helicity is forecasted to be around 150 m2s2 which studies have shown is more than adequate in SNE.

Interesting, are you saying that helicity values don't have to be quite as high in SNE as they might elsewhere, in order to get tornadic cells? Has this actually been studied? It would make sense, we seldom get the really high helicities like out west but we do get tornadoes... But I'd always assumed helicity was more or less absolute regardless of topography.

After looking a little more at the models I agree that Tuesday has definite possibilities. But once again it looks to me like the best shear and instability aren't really going to be co-located, so we're looking at (yet again) a situation where only a small area (or areas) would have the really tasty tornadic parameters.

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Interesting, are you saying that helicity values don't have to be quite as high in SNE as they might elsewhere, in order to get tornadic cells? Has this actually been studied? It would make sense, we seldom get the really high helicities like out west but we do get tornadoes... But I'd always assumed helicity was more or less absolute regardless of topography.

After looking a little more at the models I agree that Tuesday has definite possibilities. But once again it looks to me like the best shear and instability aren't really going to be co-located, so we're looking at (yet again) a situation where only a small area (or areas) would have the really tasty tornadic parameters.

You only need those large amounts of helicity (>250-300 m2s2) to get the large/strong/violent tornadoes. Even in other parts of the country 150-200 m2s2 can be plenty enough to produce weak tornadoes given other parameters are favorable as well.

The thing is though with Tuesday is 0-3km helicity is going to be fairly high (~150 m2s2) with 0-1km helicity probably around 100 m2s2 or so. This is b/c the low-level shear is pretty weak but b/c shear increases with height and changes direction we'll see larger 0-3km values.

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I don't have a lot of time today but I just wanted to stop in and say that I really like the way tomorrow is coming together for portions of New England and I agree with the new slight risk. In the end, the lack of strong lift may prevent widespread severe but that may also prevent widespread anvil contamination / linear system. (which is what happened yesterday in the Mid Atlantic. Although, I did get some nice mammatus). All you really need is to get 1 nasty supercell sparked and the thermodynamic environment will send it through the roof....

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