Potential significant severe weather Wednesday

[Dark Energy]

i just wish the trof wasn't so far N into Canada. If we had it a bit further south and sinking that way, like it is @ 72 hr on the 00z runs tonight, the forcing would be so much better. Meh.

[NaoPos]

0z Nam...

[weatherwiz]

i just wish the trof wasn't so far N into Canada. If we had it a bit further south and sinking that way, like it is @ 72 hr on the 00z runs tonight, the forcing would be so much better. Meh.

Well the past several models runs, even the what seems to be lost NAM has been coming further south with the trough, I actually like the current position of it right now. Parts of the area are going to be in the RRQ of the MLJ which is pretty potent and there should be good forcing from the pre-frontal trough/cold front. Right now there is a pretty good balance of thermodynamics and kinematics on the GFS...and with support from the SREFS.

The only issues I see right now are the issues being presented by the NAM where the mid-level front comes through too soon and we dry things out big time aloft and it mixes down to the sfc...also have to watch out for veering winds around the pre-frontal trough which could also dry things out.

Other than these issues things look pretty good IMO.

[Isotherm]

i just wish the trof wasn't so far N into Canada. If we had it a bit further south and sinking that way, like it is @ 72 hr on the 00z runs tonight, the forcing would be so much better. Meh.

Yeah I'd like to see the height fall center further south, but beggers can't be choosers here in the Northeast; we'll take what we can get. And it does still look potentially impressive overall.

[Dark Energy]

Well the past several models runs, even the what seems to be lost NAM has been coming further south with the trough, I actually like the current position of it right now. Parts of the area are going to be in the RRQ of the MLJ which is pretty potent and there should be good forcing from the pre-frontal trough/cold front. Right now there is a pretty good balance of thermodynamics and kinematics on the GFS...and with support from the SREFS.

The only issues I see right now are the issues being presented by the NAM where the mid-level front comes through too soon and we dry things out big time aloft and it mixes down to the sfc...also have to watch out for veering winds around the pre-frontal trough which could also dry things out.

Other than these issues things look pretty good IMO.

i can see your point. It's just me. I like better forcing in these kind of events. The bulk shear is over 30 kt on the latest SREF so that is a change from earlier. We need to hold that true.

[earthlight]

Well the past several models runs, even the what seems to be lost NAM has been coming further south with the trough, I actually like the current position of it right now. Parts of the area are going to be in the RRQ of the MLJ which is pretty potent and there should be good forcing from the pre-frontal trough/cold front. Right now there is a pretty good balance of thermodynamics and kinematics on the GFS...and with support from the SREFS.

The only issues I see right now are the issues being presented by the NAM where the mid-level front comes through too soon and we dry things out big time aloft and it mixes down to the sfc...also have to watch out for veering winds around the pre-frontal trough which could also dry things out.

Other than these issues things look pretty good IMO.

Yeah I pretty much agree with this. I like the positioning on the GFS better than the NAM, though. The GFS has the ridge stronger and the shortwave farther south, the height falls are more impressive from 12 to 00z Wednesday when compared to the NAM.

Although we won't really know for a few model runs--I wouldn't throw my eggs into the NAM's basket right now with that pre-frontal mid level crap it's got going on around 15z Wednesday with the 10m wind shift ahead of the what-would-be convective development. The GFS has been much steadier--as have the SREFs.

Interesting to see the GFS have such high dew points tonight...75 F + throughout New Jersey into New York City. I would throw up a flag and say overdone, but the SREF has a 90% (yes, 90%) prob of 70 F+ dew points over Central and Northern New Jersey Wednesday. With the 700-500mb lapse rates forecast to be near or better than 7 C...we're going to have some really impressive instability parameters to go along with 30+kts of 0-6km bulk shear and effective shear.

[weatherwiz]

i can see your point. It's just me. I like better forcing in these kind of events. The bulk shear is over 30 kt on the latest SREF so that is a change from earlier. We need to hold that true.

Yeah we have definitely seen the latest trends for stronger bulk winds which is certainly a good thing.

The only thing that would probably happen with the trough being further south is we would probably see a much larger tornado threat.

[nzucker]

Yeah we have definitely seen the latest trends for stronger bulk winds which is certainly a good thing.

The only thing that would probably happen with the trough being further south is we would probably see a much larger tornado threat.

If the low were further south, it would look a lot like the June 1953 outbreak which had the F4/F5 in ORH. That was a similar set-up with a low pressure tracking through Quebec, a warm front passing through SNE, and a cold front back in Upstate NY. It was also preceded by a big heat wave.

[Dark Energy]

Yeah I pretty much agree with this. I like the positioning on the GFS better than the NAM, though. The GFS has the ridge stronger and the shortwave farther south, the height falls are more impressive from 12 to 00z Wednesday when compared to the NAM.

Although we won't really know for a few model runs--I wouldn't throw my eggs into the NAM's basket right now with that pre-frontal mid level crap it's got going on around 15z Wednesday with the 10m wind shift ahead of the what-would-be convective development. The GFS has been much steadier--as have the SREFs.

Interesting to see the GFS have such high dew points tonight...75 F + throughout New Jersey into New York City. I would throw up a flag and say overdone, but the SREF has a 90% (yes, 90%) prob of 70 F+ dew points over Central and Northern New Jersey Wednesday. With the 700-500mb lapse rates forecast to be near or better than 7 C...we're going to have some really impressive instability parameters to go along with 30+kts of 0-6km bulk shear and effective shear.

Well, Tds are often grossly overdone on both models around here. So take it fwiw.

[weatherwiz]

Yeah I pretty much agree with this. I like the positioning on the GFS better than the NAM, though. The GFS has the ridge stronger and the shortwave farther south, the height falls are more impressive from 12 to 00z Wednesday when compared to the NAM.

Although we won't really know for a few model runs--I wouldn't throw my eggs into the NAM's basket right now with that pre-frontal mid level crap it's got going on around 15z Wednesday with the 10m wind shift ahead of the what-would-be convective development. The GFS has been much steadier--as have the SREFs.

Interesting to see the GFS have such high dew points tonight...75 F + throughout New Jersey into New York City. I would throw up a flag and say overdone, but the SREF has a 90% (yes, 90%) prob of 70 F+ dew points over Central and Northern New Jersey Wednesday. With the 700-500mb lapse rates forecast to be near or better than 7 C...we're going to have some really impressive instability parameters to go along with 30+kts of 0-6km bulk shear and effective shear.

Yeah the positioning on the GFS is certainly better and has been improving with each model run. With that s/w further south and the stronger ridge that's also really helping to further increase the winds aloft thanks to the pressure gradient and it's leading to the stronger height falls as you mentioned.

The dewpoint situation is interesting, usually were looking at the NAM which is overdoing things...very rarely do we actually see the GFS be this full blown with the dewpoints. Like you said, GREAT SREF support for this and if you look at the theta-e advection there is a GREAT deal of that...I could definitely see some dewpoint pooling. If we could get dews this high that would really benefit, especially if we see any drying in the mid-levels.

[weatherwiz]

If the low were further south, it would look a lot like the June 1953 outbreak which had the F4/F5 in ORH. That was a similar set-up with a low pressure tracking through Quebec, a warm front passing through SNE, and a cold front back in Upstate NY. It was also preceded by a big heat wave.

Yeah it would have some similarities but it's not like that is the only setup we've had like that...we've had others.

Usually all are severe wx setups in the summer consist of that...sfc low to our NW, warm front lifting north, and cold front sliding east...it's just this time we actually may have an EML and good dynamics.

We'll see what happens!

[earthlight]

Well, Tds are often grossly overdone on both models around here. So take it fwiw.

You know it's interesting--I usually toss the dew points on most models at this range completely, but they have been running rather high in this airmass. I've seen some of the local area OBS come in with some very high dew points the past few days. I guess what I'm saying is, I am a little less hesitant to throw them out completely--especially with the SREF offering a 90% probability of dew points over 70 F.

[weatherwiz]

You know it's interesting--I usually toss the dew points on most models at this range completely, but they have been running rather high in this airmass. I've seen some of the local area OBS come in with some very high dew points the past few days. I guess what I'm saying is, I am a little less hesitant to throw them out completely--especially with the SREF offering a 90% probability of dew points over 70 F.

Even if dewpoints end up being 68-70F that's still plenty good enough, especially with steep mid-level lapse rates. The NAM does offer this but it has that damn mid level front push through drying out the mid levels and then mixing down to the sfc so the sfc dews fall to the low 60's.

As far as I see it dews over 70F are just a bonus.

[Dark Energy]

Even if dewpoints end up being 68-70F that's still plenty good enough, especially with steep mid-level lapse rates. The NAM does offer this but it has that damn mid level front push through drying out the mid levels and then mixing down to the sfc so the sfc dews fall to the low 60's.

As far as I see it dews over 70F are just a bonus.

agree. I know i should know this, but its 2 am and im tired. I wonder what the difference in CAPE would be with Tds in the 65-70 range compared to 70-75 range. I know it is a lot, but i wonder how much given the EML.

[weatherwiz]

agree. I know i should know this, but its 2 am and im tired. I wonder what the difference in CAPE would be with Tds in the 65-70 range compared to 70-75 range. I know it is a lot, but i wonder how much given the EML.

That's a good question actually...I would think it's in the 1250-1800 J/KG range...but given the EML perhaps the difference is not as extreme.

[NJwinter23]

That's a good question actually...I would think it's in the 1250-1800 J/KG range...but given the EML perhaps the difference is not as extreme.

I definitely can't calculate that lol but that makes sense the way I'm visualizing it. In terms of a severe weather threat in general though, given there is an EML in place, lower Td's would make for a stronger cap? That would be the more noticeable difference to me as I'd think the CAPE will be enough for severe either way, Td=65 or 70+... Of course forcing doesnt look like an issue on Wed either

[NJwinter23]

and in perhaps a prequel to what we might see across some of the northeast on Wednesday, SPC has a moderate risk/45% wind for portions of the Great Lakes today.

[Dark Energy]

That's a good question actually...I would think it's in the 1250-1800 J/KG range...but given the EML perhaps the difference is not as extreme.

That makes sense. I know some of the huge CAPE soundings I have seen have had Tds of 73-76F. And those had very low LCLs and thus a huge profile. Those were on the order of 5k CAPE or more. I dont see that here, but still it would make a difference with Tds of 70 or better. WHen you have an EML and low LCLs, you can get some pretty amazing CAPE.

[weatherwiz]

I definitely can't calculate that lol but that makes sense the way I'm visualizing it. In terms of a severe weather threat in general though, given there is an EML in place, lower Td's would make for a stronger cap? That would be the more noticeable difference to me as I'd think the CAPE will be enough for severe either way, Td=65 or 70+... Of course forcing doesnt look like an issue on Wed either

I actually didn't think of that...it could make for a stronger cap, although would this also depend on the level of dry air in the area that is capped?

One way I cape up with that number was just by looking at the NAM/GFS.

The GFS has the EML and it has the very high dews and with this capes are well over 2500-4000 J/KG...granted it's actually also much warmer with sfc temps...at least here in SNE.

The NAM doesn't have the EML, and while it still is somewhat high with dews, upper 60's, it lowers the dews during the afternoon and with that instability decreases and things don't become as unstable. The NAM has generally 1200-1800 J/KG of cape.

I agree though, CAPE should definitely be good enough for severe...just a matter of how widespread the severe threat is.

[weatherwiz]

That makes sense. I know some of the huge CAPE soundings I have seen have had Tds of 73-76F. And those had very low LCLs and thus a huge profile. Those were on the order of 5k CAPE or more. I dont see that here, but still it would make a difference with Tds of 70 or better. WHen you have an EML and low LCLs, you can get some pretty amazing CAPE.

Yeah if we can materialize this EML and dews like the GFS are showing we could certainly see some impressive cape...already pretty decent showing of 2500-4000 J/KG...actually too, LI values are looking quite impressive as well...as low as -8C.

If temps can get into the upper 80's to near 90F with sfc dews in the lower 70's and the EML that will lead to some impressive convective indices.

[Dark Energy]

http://www.spc.noaa....k/day2otlk.html

Interesting. Keeps the higher probs just to our N. at least for NYC

Edit, their higher probs are almost right near NYC. my bad.

[NJwinter23]

I actually didn't think of that...it could make for a stronger cap, although would this also depend on the level of dry air in the area that is capped?

One way I cape up with that number was just by looking at the NAM/GFS.

The GFS has the EML and it has the very high dews and with this capes are well over 2500-4000 J/KG...granted it's actually also much warmer with sfc temps...at least here in SNE.

The NAM doesn't have the EML, and while it still is somewhat high with dews, upper 60's, it lowers the dews during the afternoon and with that instability decreases and things don't become as unstable. The NAM has generally 1200-1800 J/KG of cape.

I agree though, CAPE should definitely be good enough for severe...just a matter of how widespread the severe threat is.

All else being equal, I was just picturing a higher/cooler LCL when I mentioned that and hence a stronger inversion above it....I'm sure it is far from being that simple though.

The mixing issue I'm sure will be interesting on Wed. If an EML advects in and a good westward/downsloping component to the surface wind exists (With the surface heating), will drier air from the mid-levels tend to contaminate the boundary layer? How is moisture advection at the surface on Wednesday?

Like I said before though, I'd love to get those mid-level lapse rates in and work from there

[NJwinter23]

Furthermore I'd take it the difference in SPC's 15% to the south and 30% to the north right now at day 2 is strictly on a wind shear basis (the greater shear being expected further north obviously). I'm pretty confident wherever can manage 30kts+ 0-6km shear will be in business Wed. in the expected thermodynamic environment

[nzucker]

All else being equal, I was just picturing a higher/cooler LCL when I mentioned that and hence a stronger inversion above it....I'm sure it is far from being that simple though.

The mixing issue I'm sure will be interesting on Wed. If an EML advects in and a good westward/downsloping component to the surface wind exists (With the surface heating), will drier air from the mid-levels tend to contaminate the boundary layer? How is moisture advection at the surface on Wednesday?

Like I said before though, I'd love to get those mid-level lapse rates in and work from there

I think the key is to maintain a SSW wind at the surface so we have good advection of higher dewpoints with less of a downsloping flow, this also creating shear since flow in the upper levels is from the WNW as the trough moves through. Most of the soundings are showing pretty good turning, but I'd like to see us maintain the current humidity and not have too much downsloping. If the front goes through earlier in the day as the NAM has shown on some runs, we won't have the best kinematics at the time when instability is really increasing in the afternoon hours.

[Dark Energy]

Furthermore I'd take it the difference in SPC's 15% to the south and 30% to the north right now at day 2 is strictly on a wind shear basis (the greater shear being expected further north obviously). I'm pretty confident wherever can manage 30kts+ 0-6km shear will be in business Wed. in the expected thermodynamic environment

yea, true. all we need is 30 kt of bulk shear in my book and we are set. we see that, and we are good. I've seen plenty of SVR here with that shear.

[weatherwiz]

All else being equal, I was just picturing a higher/cooler LCL when I mentioned that and hence a stronger inversion above it....I'm sure it is far from being that simple though.

The mixing issue I'm sure will be interesting on Wed. If an EML advects in and a good westward/downsloping component to the surface wind exists (With the surface heating), will drier air from the mid-levels tend to contaminate the boundary layer? How is moisture advection at the surface on Wednesday?

Like I said before though, I'd love to get those mid-level lapse rates in and work from there

I see what you mean on that...makes sense, and yeah it's probably much more complex than that but it's just a general idea

Yeah sfc winds and BL winds are really going to be key on Wednesday...if the warm front does blow through though, which it should winds should be more SSW/SW then like WSW...however, with the pre-frontal trough if they do veer more WSW then that could spell trouble.

[NJwinter23]

I feel I am also being a little too skeptical here as well, almost fearing that things will not shape up PERFECTLY on Wed. While I'd love to track a massive derecho with embedded supercells dropping southeast on Wed, I'll be realistic and accept the over all nice threat for strong thunderstorms on Wed, and be very happy with it...Haven't seen any action down by me yet.

[nzucker]

I feel I am also being a little too skeptical here as well, almost fearing that things will not shape up PERFECTLY on Wed. While I'd love to track a massive derecho with embedded supercells dropping southeast on Wed, I'll be realistic and accept the over all nice threat for strong thunderstorms on Wed, and be very happy with it...Haven't seen any action down by me yet.

Are you thinking this is a significant tornado threat?

[Dark Energy]

Are you thinking this is a significant tornado threat?

i dont see that.

[weatherwiz]

I feel I am also being a little too skeptical here as well, almost fearing that things will not shape up PERFECTLY on Wed. While I'd love to track a massive derecho with embedded supercells dropping southeast on Wed, I'll be realistic and accept the over all nice threat for strong thunderstorms on Wed, and be very happy with it...Haven't seen any action down by me yet.

Always good reason to be skeptical around here

I'm certainly skeptical as well...at least when it comes to the potential for a widespread outbreak. I think we definitely will see severe wx on Wednesday it's just a question of how widespread of an event will it be?

I'm also intrigued by the supercell potential, especially up this way b/c some of the hodos are quite impressive so if we see any supercells fire they could become interesting very quickly.

The flow aloft is fairly unidirectional but the lowest 3-4km of the atmosphere exhibits a good deal of turning so we could see something where the storm mode early on is supercells with them quickly forming a line, or we see a line develop with supercells out ahead of it.

I think it will also depend if it's the pre-frontal trough that's more active or the cold front.