tornadotony Posted June 15, 2014 Share Posted June 15, 2014 As has been the case all year, model trends in the final stretch are not looking favorable for tomorrow, IMHO. Yesterday's runs had me increasingly excited about E NE and W IA during the afternoon and evening, and last night's 4 km NAM depicted prolific supercells developing within the reservoir of 4000-6000 J/kg SBCAPE and traversing that region. The trend today has been toward morning initiation right along the boundary in SD/MN, with storms growing upscale quickly and transforming the baroclinic zone from a nice late-season warm front to yet another outflow-reinforced, discontinuous density current surging south. This is eerily similar to what happened in NE on June 3, the HIGH risk day. Granted, I'm not dismissing the tornado potential with the activity along the boundary, even if it develops early in the day. But it would be yet another messy scenario with tempered likelihood of long-track, strong tornadoes. If convective initiation can manage to occur to the south away from any ongoing MCS during the late afternoon or evening, this still looks very volatile. But there isn't a lot of model support for that on today's guidance. I will note, though, that overall there's been a bit of a bias toward underforecasting convection in the Plains this year. Though I generally agree with this, I'd add that the last sentence is the most important part, especially in the context that the high-res/convection-allowing models have seemed particularly poor in convective forecasting any more than 24 h out recently, though that has worked both ways in many instances. Link to comment Share on other sites More sharing options...
thewxmann Posted June 15, 2014 Share Posted June 15, 2014 As has been the case all year, model trends in the final stretch are not looking favorable for tomorrow, IMHO. Yesterday's runs had me increasingly excited about E NE and W IA during the afternoon and evening, and last night's 4 km NAM depicted prolific supercells developing within the reservoir of 4000-6000 J/kg SBCAPE and traversing that region. The trend today has been toward morning initiation right along the boundary in SD/MN, with storms growing upscale quickly and transforming the baroclinic zone from a nice late-season warm front to yet another outflow-reinforced, discontinuous density current surging south. This is eerily similar to what happened in NE on June 3, the HIGH risk day. Granted, I'm not dismissing the tornado potential with the activity along the boundary, even if it develops early in the day. But it would be yet another messy scenario with tempered likelihood of long-track, strong tornadoes. If convective initiation can manage to occur to the south away from any ongoing MCS during the late afternoon or evening, this still looks very volatile. But there isn't a lot of model support for that on today's guidance. I will note, though, that overall there's been a bit of a bias toward underforecasting convection in the Plains this year. Agree wholeheartedly with the first paragraph. Link to comment Share on other sites More sharing options...
Santa Clause Posted June 15, 2014 Share Posted June 15, 2014 So guys, is this going to MCS in a hurry, or is there still a chance for discrete development in E NE and IA? Have family in Storm Lake, just interested in the expert opinion with so many talented posters in here. Link to comment Share on other sites More sharing options...
tornadotony Posted June 15, 2014 Share Posted June 15, 2014 So guys, is this going to MCS in a hurry, or is there still a chance for discrete development in E NE and IA? Have family in Storm Lake, just interested in the expert opinion with so many talented posters in here. There's definitely still a shot at discrete supercells in that area. In fact, the 18z GFS tends to support more discrete evolution. It'll be interesting to see how the mesoscale evolves, where the warm front sets up, and where initiation takes place tomorrow. Link to comment Share on other sites More sharing options...
andyhb Posted June 15, 2014 Author Share Posted June 15, 2014 If convective initiation can manage to occur to the south away from any ongoing MCS during the late afternoon or evening, this still looks very volatile. But there isn't a lot of model support for that on today's guidance. I will note, though, that overall there's been a bit of a bias toward underforecasting convection in the Plains this year. I think there's a better shot at discrete initiation tomorrow to the south than there was on 6/3 since we don't have 15˚C 700 mb temperatures overspreading the warm sector. The subtle forcing with this low amplitude wave appears rather conducive for a discrete storm mode. The deep layer shear vectors also appear more conducive off the dryline tomorrow unlike yesterday where they were more parallel to the boundary. I mean, it's another tough, conditional setup since if we do get several supercells going, all holy hell is going to break loose. Link to comment Share on other sites More sharing options...
Thunder Road Posted June 15, 2014 Share Posted June 15, 2014 After 6/3 I said I wouldn't chase another warm front. I didn't think I'd be breaking that promise so soon... What I don't like about the DL play is that the NAM has surface winds veering out along it. Apparently that's a known bias? Although yesterday we noticed it happening as well, the wind was due southerly or slightly west of south just ahead of the dryline, so the NAM may not have been all that wrong. Even the GFS has due southerlies for tomorrow at 21z vs runs before yesterday when it had (roughly) 140 or so for a direction. Meanwhile, of course all of the usual caveats to a WF are in play tomorrow. I'll decide in the morning what I'm doing. Link to comment Share on other sites More sharing options...
brettjrob Posted June 15, 2014 Share Posted June 15, 2014 I think there's a better shot at discrete initiation tomorrow to the south than there was on 6/3 since we don't have 15˚C 700 mb temperatures overspreading the warm sector. The subtle forcing with this low amplitude wave appears rather conducive for a discrete storm mode. The deep layer shear vectors also appear more conducive off the dryline tomorrow unlike yesterday where they were more parallel to the boundary. I mean, it's another tough, conditional setup since if we do get several supercells going, all holy hell is going to break loose. Yeah, I definitely wouldn't worry about mode along the dryline or over the warm sector farther south; that's about as clear as it gets. I'm much more worried about a cap bust, as the best forcing seems to pass through NE by mid-late afternoon with shortwave ridging possible in its wake. Link to comment Share on other sites More sharing options...
Stebo Posted June 15, 2014 Share Posted June 15, 2014 After 6/3 I said I wouldn't chase another warm front. I didn't think I'd be breaking that promise so soon... What I don't like about the DL play is that the NAM has surface winds veering out along it. Apparently that's a known bias? Although yesterday we noticed it happening as well, the wind was due southerly or slightly west of south just ahead of the dryline, so the NAM may not have been all that wrong. Even the GFS has due southerlies for tomorrow at 21z vs runs before yesterday when it had (roughly) 140 or so for a direction. Meanwhile, of course all of the usual caveats to a WF are in play tomorrow. I'll decide in the morning what I'm doing. Yes that is a known bias of the NAM. I am usually highly skeptical of the NAM's low level wind profile until the day of, which it usually trends toward the other models. Link to comment Share on other sites More sharing options...
David Reimer Posted June 15, 2014 Share Posted June 15, 2014 Really? Are you sure? I'm not stupid, I realize that, thanks. I'm sorry but did I miss something? If my intention was to talk down to you trust me you would know it. I was simply pointing out the issue of chasing in an environment with multiple possibly tornadic supercells in close proximity. In addition you can bet there will be one big chaser convergence in the area tomorrow which will add to the danger. Even with a linear MCS mode I bet we'll be seeing some mighty impressive wind gusts tomorrow with all that CAPE. It should be fun from a computer-chase standpoint! Link to comment Share on other sites More sharing options...
ZackH Posted June 15, 2014 Share Posted June 15, 2014 I'm wanting to give this a chance chase wise because it may very well be my last chance for a major day before starting my new job in Bismarck... but I will have a hard time leaving GFK before 11 AM... with the potential early initiation on the warm front, I'm nervous about getting down there in time. It's about a 4-6 hour drive for me depending on location. I may try to get the son in day care a bit earlier just in case. Link to comment Share on other sites More sharing options...
bdgwx Posted June 15, 2014 Share Posted June 15, 2014 Some of the storm scale models are showing some long discrete updraft helicity tracks for cells exiting SD/NE area and going into MN/IA area. It looks like things will eventually upscale into an MCS, but if the models are right then it will be one wicked MCS with 5000 j/kg getting forced into the leading edge with some incredible wind shear across the board. Link to comment Share on other sites More sharing options...
hm8 Posted June 16, 2014 Share Posted June 16, 2014 Spc wrf resolved that SD cell in an interesting way... Link to comment Share on other sites More sharing options...
Santa Clause Posted June 16, 2014 Share Posted June 16, 2014 Is this going to be another case where the discrete nature of the cells is lost within an hour or two of initiation? Seems like that's been the trend lately. Link to comment Share on other sites More sharing options...
andyhb Posted June 16, 2014 Author Share Posted June 16, 2014 Is this going to be another case where the discrete nature of the cells is lost within an hour or two of initiation? Seems like that's been the trend lately. You almost want to assume that given the way this year has gone, but the probability of intense supercells tomorrow is almost guaranteed if discrete mode is dominant for any decent length of time. It's really going to come down to nowcasting again. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted June 16, 2014 Share Posted June 16, 2014 It's funny how people continue to say "the trend has been" blah blah blah. Yes, it's been a bad year but the atmosphere will do what it wants on any given day and every setup is different. Link to comment Share on other sites More sharing options...
nwburbschaser Posted June 16, 2014 Share Posted June 16, 2014 It's funny how people continue to say "the trend has been" blah blah blah. Yes, it's been a bad year but the atmosphere will do what it wants on any given day and every setup is different. Bingo. Link to comment Share on other sites More sharing options...
tornadotony Posted June 16, 2014 Share Posted June 16, 2014 It's funny how people continue to say "the trend has been" blah blah blah. Yes, it's been a bad year but the atmosphere will do what it wants on any given day and every setup is different. THANK YOU. Link to comment Share on other sites More sharing options...
Stebo Posted June 16, 2014 Share Posted June 16, 2014 It's funny how people continue to say "the trend has been" blah blah blah. Yes, it's been a bad year but the atmosphere will do what it wants on any given day and every setup is different.Yes, and given the potential instability and shear that should be in place even if things were to go linear within a few hours, the period before that could have a very significant potential for tornadoes and very large hail. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted June 16, 2014 Share Posted June 16, 2014 The 0z NAM blows up SO MUCH PRECIP as early as 15z. Do not like that at all. Link to comment Share on other sites More sharing options...
andyhb Posted June 16, 2014 Author Share Posted June 16, 2014 The 0z NAM blows up SO MUCH PRECIP as early as 15z. Do not like that at all. This, it appears to go messy quite early on, although I think there's a window of discrete mode in there (and also looks like it fires a big cell in N KS later on with some extreme low level shear in the vicinity). Regardless, the NAM has been junk even from short range recently, I only really commented on the 18z run because the soundings it was putting out were so absurd. The parameters already are impressive at 15z. Link to comment Share on other sites More sharing options...
tornadotony Posted June 16, 2014 Share Posted June 16, 2014 The 0z NAM blows up SO MUCH PRECIP as early as 15z. Do not like that at all. It's all N of the warm sector. Warm sector blows around 18z but the parameters are so off the charts with storms likely to be sfc-based that timing shouldn't matter. This is looking like an increasingly dangerous tornado threat tomorrow starting around 17-18z. Link to comment Share on other sites More sharing options...
tornadotony Posted June 16, 2014 Share Posted June 16, 2014 18z at Columbus, NE. This is a dangerous tornado sounding for discrete cells. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted June 16, 2014 Share Posted June 16, 2014 It's all N of the warm sector. Warm sector blows around 18z but the parameters are so off the charts with storms likely to be sfc-based that timing shouldn't matter. This is looking like an increasingly dangerous tornado threat tomorrow starting around 17-18z. Starting in eastern NE as it looks now. Link to comment Share on other sites More sharing options...
andyhb Posted June 16, 2014 Author Share Posted June 16, 2014 18z at Columbus, NE. This is a dangerous tornado sounding for discrete cells. Clean wind profile, strong directional shear, steep mid level lapse rates, very moist low levels...yeah that'll do the trick. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted June 16, 2014 Share Posted June 16, 2014 The 0z 4km NAM looks to have much less precip then a discrete QPF track near/west of Sioux City at 21z, south of the ongoing convection to the north Link to comment Share on other sites More sharing options...
kevinbente Posted June 16, 2014 Share Posted June 16, 2014 Dang. Some of the hodos I'm seeing on the 0z NAM are pretty nasty looking. Link to comment Share on other sites More sharing options...
brettjrob Posted June 16, 2014 Share Posted June 16, 2014 The 0z 4km NAM looks to have much less precip then a discrete QPF track near/west of Sioux City at 21z, south of the ongoing convection to the north Early/widespread warm sector initiation on the NAM12 vs. virtually none on the NAM4 (looks like that swath is a short-lived cell that only briefly attains any UH before getting munched by the MCS). Helps so much on the go/no go decision, right? Love 2014. Link to comment Share on other sites More sharing options...
bdgwx Posted June 16, 2014 Share Posted June 16, 2014 Updraft helicity from the 0Z 4km NAM shows two wide tracks at 18Z in eastern SD with 4000 j/kg of SBCAPE and 30 kts of 0-1 km shear ahead of that lead track. At 06Z it peaks the MCS with 90+ knot winds at 850mb. Link to comment Share on other sites More sharing options...
Jayhawkers Posted June 16, 2014 Share Posted June 16, 2014 I find it funny how people keep resorting to the NAM--including myself-- despite how absolutely awful it's been this year with almost everything, even this close to the event, seems to overexadgerate a lot. Link to comment Share on other sites More sharing options...
bdgwx Posted June 16, 2014 Share Posted June 16, 2014 It's definitely the over achiever for sure. Check out hour 06Z from the 0Z 4km NAM run. It is showing a 20mb pressure perturbation from the MCS over a distance of about 100 miles. For what it's worth though it did pretty well with the location and intensity of the Omaha cell a week or two ago, but failed badly with the MCS. Link to comment Share on other sites More sharing options...
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