TheWeatherPimp Posted April 7, 2011 Share Posted April 7, 2011 Still not sure what to think about this weekend, so many questions that still need answered. I honestly think Saturday has the best tornado potential with Sunday becoming a massive damaging wind day. Link to comment Share on other sites More sharing options...
Ed Lizard Posted April 7, 2011 Share Posted April 7, 2011 Could be some significant moisture depth issues on Saturday across the four-state corner region of NE/KS/MO/IA. Looks like the moisture depth there is pretty shallow to begin with, and an EML surge in the wake of a mid level s/w causes it to mix out big time during the heat of the day. A strengthening synoptic LLJ looks to help replenish some of that in the late afternoon, but it's hard to tell whether that will be enough. This is what I was talking about before. The entire state of Iowa looks almost dry. Except for Southern Illionois and extending East, everything seems mainly North of LOT. Link to comment Share on other sites More sharing options...
KokomoWX Posted April 7, 2011 Share Posted April 7, 2011 <br /><br /><br /> Which met's Facebook was that?<br /> <br /><br /><br />Izzi Sent from my ADR6400L using Tapatalk Link to comment Share on other sites More sharing options...
csnavywx Posted April 7, 2011 Share Posted April 7, 2011 This is what I was talking about before. The entire state of Iowa looks almost dry. Except for Southern Illionois and extending East, everything seems mainly North of LOT. Granted, that's the NAM, which can be notoriously bad with convective initiation (look at last Sunday), but the SREF members are underlining this problem in the latest run (09z). May have to end up hugging the moisture surge late in the day and look for where that crosses the boundary to get some decent supercells. Sunday is looking much better for something widespread. Link to comment Share on other sites More sharing options...
Hoosier Posted April 7, 2011 Share Posted April 7, 2011 Still not sure what to think about this weekend, so many questions that still need answered. I honestly think Saturday has the best tornado potential with Sunday becoming a massive damaging wind day. The rapid deepening of the surface low on Sunday will force surface winds to back or at least not be too veered. The main problem for a big/widespread tornado threat is how sharp/amplified this trough looks. Another question is how far out ahead of the cold front that the storms will go up. Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted April 7, 2011 Share Posted April 7, 2011 The rapid deepening of the surface low on Sunday will force surface winds to back or at least not be too veered. The main problem for a big/widespread tornado threat is how sharp/amplified this trough looks. Another question is how far out ahead of the cold front that the storms will go up. I'm hoping we can get some boundaries to lay out on Sunday to provide focal points for convection - particularly across Illinois/Western Indiana Link to comment Share on other sites More sharing options...
Hoosier Posted April 7, 2011 Share Posted April 7, 2011 From a synoptic standpoint, can anyone think of a good analog for this event, preferably one during the month of April? Link to comment Share on other sites More sharing options...
CUmet Posted April 7, 2011 Share Posted April 7, 2011 The rapid deepening of the surface low on Sunday will force surface winds to back or at least not be too veered. The main problem for a big/widespread tornado threat is how sharp/amplified this trough looks. Another question is how far out ahead of the cold front that the storms will go up. In this case, the surface winds might be too veered given the sharpness of the trough, due to the backed nature of the mid-upper level flow. One concern I have is that the deepening of the low and pressure falls occur pretty distantly north, which makes it more difficult for surface winds to back over the warm sector. To be sure, it helps to some extent, but will it be enough? The sharpness of the trough narrows the margin for error considerably. Taking the 12z GFS verbatim, it looks like a somewhat linear or mixed-mode event, but there is the possibility that the surface winds may end up being slightly more backed due to small-scale features, and there could still be changes in the trough configuration. Link to comment Share on other sites More sharing options...
Hoosier Posted April 7, 2011 Share Posted April 7, 2011 Stunning to see mid 60's dewpoints being progged into northern Wisconsin even if it's overdone. Link to comment Share on other sites More sharing options...
Hoosier Posted April 7, 2011 Share Posted April 7, 2011 In this case, the surface winds might be too veered given the sharpness of the trough, due to the backed nature of the mid-upper level flow. One concern I have is that the deepening of the low and pressure falls occur pretty distantly north, which makes it more difficult for surface winds to back over the warm sector. To be sure, it helps to some extent, but will it be enough? The sharpness of the trough narrows the margin for error considerably. Taking the 12z GFS verbatim, it looks like a somewhat linear or mixed-mode event, but there is the possibility that the surface winds may end up being slightly more backed due to small-scale features, and there could still be changes in the trough configuration. Yeah you get the feeling we're near the tipping point. It wouldn't take much of a change in the mid/upper level flow to ramp up the tornado risk substantially. Despite the timing issues, models have been pretty consistent recently in the look of the trough. Link to comment Share on other sites More sharing options...
Hoosier Posted April 7, 2011 Share Posted April 7, 2011 Our first look at Sunday evening on the SREF Link to comment Share on other sites More sharing options...
wisconsinwx Posted April 7, 2011 Share Posted April 7, 2011 Our first look at Sunday evening on the SREF So, is anyone going to travel up here to storm chase perhaps?? Link to comment Share on other sites More sharing options...
Ed Lizard Posted April 7, 2011 Share Posted April 7, 2011 GFS looks a little more interesting on Hour 24-84 precip. Forecast EHIs of 15 and 100% agreement of the short ensembles on C-B over 50,000 don't mean much if storms never form. Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted April 7, 2011 Share Posted April 7, 2011 GFS looks a little more interesting on Hour 24-84 precip. Forecast EHIs of 15 and 100% agreement of the short ensembles on C-B over 50,000 don't mean much if storms never form. Using the GFS and NAM to forecast storm development, especially when you are over 48 hours out is practically useless. Link to comment Share on other sites More sharing options...
Ed Lizard Posted April 7, 2011 Share Posted April 7, 2011 Storms just West of Des Moines per GFS Saturday evening... Link to comment Share on other sites More sharing options...
Ed Lizard Posted April 7, 2011 Share Posted April 7, 2011 Using the GFS and NAM to forecast storm development, especially when you are over 48 hours out is practically useless. Just noting people are posting all varieties of model and ensemble severe parameters for areas some models keep capped. Huge difference though, NAM vs GFS, NAM suggests a disappointing weekend for severe fans, GFS doesn't. Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted April 7, 2011 Share Posted April 7, 2011 Northern/Northwestern/Western Illinois really look good on the 12z GFS for Sunday - with higher instability and backed surface winds. Link to comment Share on other sites More sharing options...
Chicago Storm Posted April 7, 2011 Share Posted April 7, 2011 Just noting people are posting all varieties of model and ensemble severe parameters for areas some models keep capped. Huge difference though, NAM vs GFS, NAM suggests a disappointing weekend for severe fans, GFS doesn't. Look again. Link to comment Share on other sites More sharing options...
Ed Lizard Posted April 7, 2011 Share Posted April 7, 2011 Look again. Excluding a small corner of SE Missouri into Southern Illinois, the NAM keeps most heavy precip (and I'll go out on a limb and say absence of precip is a sign of absence of storms) in Minnesota, Wisconsin and Michigan. Unless I'm really misreading the 60 hour NAM precip map. Link to comment Share on other sites More sharing options...
brettjrob Posted April 7, 2011 Share Posted April 7, 2011 Excluding a small corner of SE Missouri into Southern Illinois, the NAM keeps most heavy precip (and I'll go out on a limb and say absence of precip is a sign of absence of storms) in Minnesota, Wisconsin and Michigan. Unless I'm really misreading the 60 hour NAM precip map. No, you're right; the NAM indicates no daytime storms on the dryline or warm front for Saturday. I was fairly surprised to see that this morning. FWIW, the 00z ECMWF showed some dryline activity in KS, but nothing in IA/MN through 00z Sun. Link to comment Share on other sites More sharing options...
thewxmann Posted April 7, 2011 Share Posted April 7, 2011 Actually, if the 12Z NAM is correct, you can forget about initiation anywhere during the daytime hours. I think Brett really hit the nail on the head when he mentioned the system slowing down and hanging around the SW U.S. - timing (on Sat) and shear vectors (on Sunday) might just do it in for this system. Link to comment Share on other sites More sharing options...
VAwxman Posted April 7, 2011 Share Posted April 7, 2011 Actually, if the 12Z NAM is correct, you can forget about initiation anywhere during the daytime hours. I think Brett really hit the nail on the head when he mentioned the system slowing down and hanging around the SW U.S. - timing (on Sat) and shear vectors (on Sunday) might just do it in for this system. You'd have to define "do it in". There will be severe, no doubt. Type, coverage, etc of course in an issue. I always expect you to downplay all events anyway lol, but as I posted earlier, I'm not as excited about this one either as I was yesterday. Things could easily still change though. Link to comment Share on other sites More sharing options...
Stebo Posted April 7, 2011 Share Posted April 7, 2011 You'd have to define "do it in". There will be severe, no doubt. Type, coverage, etc of course in an issue. I always expect you to downplay all events anyway lol, but as I posted earlier, I'm not as excited about this one either as I was yesterday. Things could easily still change though. I think people need to ease up on taking the NAM for any value, the model can't get a 12 hour forecast right half the time, and we are using it as reasoning for something to not happen at 60-84 hours out.... Link to comment Share on other sites More sharing options...
csnavywx Posted April 7, 2011 Share Posted April 7, 2011 Actually, if the 12Z NAM is correct, you can forget about initiation anywhere during the daytime hours. I think Brett really hit the nail on the head when he mentioned the system slowing down and hanging around the SW U.S. - timing (on Sat) and shear vectors (on Sunday) might just do it in for this system. Like I mentioned before, relying on the NAM for convective initiation is a terrible idea at this time frame. Hell, it's not even that great inside 24 hours most of the time. Then again, there are few models that can do it well (the 4km NMM isn't bad). There's definitely enough going on Sat. afternoon/ early evening to get convection rolling, including some synoptic forcing (height falls and strengthening/backing LLJ) and a convergence boundary or two. And you'd better believe those winds will back ahead of the dryline on Sunday, especially near a bulge. Live by the models... die by the models. Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted April 7, 2011 Share Posted April 7, 2011 Like I mentioned before, relying on the NAM for convective initiation is a terrible idea at this time frame. Hell, it's not even that great inside 24 hours most of the time. Then again, there are few models that can do it well (the 4km NMM isn't bad). There's definitely enough going on Sat. afternoon/ early evening to get convection rolling, including some synoptic forcing (height falls and strengthening/backing LLJ) and a convergence boundary or two. And you'd better believe those winds will back ahead of the dryline on Sunday, especially near a bulge. Live by the models... die by the models. +100 Link to comment Share on other sites More sharing options...
David Reimer Posted April 7, 2011 Share Posted April 7, 2011 If a majority of chasers were as pessimistic as some of yall in here by using a model for convective initiation when its 36+ hours out then we wouldn't have this issue with chaser convergences. Good grief... Link to comment Share on other sites More sharing options...
Coreyback Posted April 7, 2011 Share Posted April 7, 2011 I want to say the supercell composite parameter off of the DVN sounding was like 53 or something ridiculous. Sorry to quote a (relatively) old post, but that sounding was ridiculous enough I kept it: One of those days where if something went, it would have been really impressive. But part of me was kind of glad we avoided the carnage that would have gone along with it... Link to comment Share on other sites More sharing options...
brettjrob Posted April 7, 2011 Share Posted April 7, 2011 I'm nowhere close to dismissing any day out of the Fri-Sun period at this point, but I do have to admit, it's funny how defensive certain people get when a conservative/pessimistic viewpoint is presented. I just always get the feeling here that, all else being equal, pessimistic opinions get you less leeway from criticism than bullish ones. Talking about potential scenarios and what "could happen" is fine, but remember, that works both ways. If you're willing to gloss over posts on a highly-caped day about how the triple-point "could" be prolific if something manages to break the cap, you shouldn't have any complaints when someone mentions how the cap "could" be stronger than anticipated on a day everyone's excited about, either. Link to comment Share on other sites More sharing options...
csnavywx Posted April 7, 2011 Share Posted April 7, 2011 Only difference is that we're in early April and not late June. It's generally much easier to break capping inversions this time of year due to the fact that baroclinicity (and its resultant synoptic forcing/preconditioning) hasn't waned, and can be paired with other sources of forcing on the mesoscale in addition to diabatic heating. In the summer, you typically have to rely on daytime (diabatic) heating and a boundary alone to do the work for you. Link to comment Share on other sites More sharing options...
csnavywx Posted April 7, 2011 Share Posted April 7, 2011 I'm nowhere close to dismissing any day out of the Fri-Sun period at this point, but I do have to admit, it's funny how defensive certain people get when a conservative/pessimistic viewpoint is presented. I just always get the feeling here that, all else being equal, pessimistic opinions get you less leeway from criticism than bullish ones. Talking about potential scenarios and what "could happen" is fine, but remember, that works both ways. If you're willing to gloss over posts on a highly-caped day about how the triple-point "could" be prolific if something manages to break the cap, you shouldn't have any complaints when someone mentions how the cap "could" be stronger than anticipated on a day everyone's excited about, either. I hear you, but in this case, I don't believe the capping will be as much of an issue. Mixing out too much of our shallow boundary layer moisture with the EML and not recharging it in time is a bigger threat, again, imo. Link to comment Share on other sites More sharing options...
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