cyclone77 Posted February 26, 2017 Share Posted February 26, 2017 NAM products would bring the tor threat up into southeast Iowa, and along and south of the I-80 corridor in Illinois on Tuesday. Surface low is deep enough to keep the surface winds backed beneath some pretty impressive mid-levels. Some forecast soundings are showing over 80kts of shear from the LCL to the EL. Great wind shear in the lower 1km as well. If the NAM products are on to something the slight will need to be lifted further north into these areas. Link to comment Share on other sites More sharing options...
Powerball Posted February 26, 2017 Share Posted February 26, 2017 13 hours ago, Anti tornado said: Happened to see this on twitter. Impressive cape and sufficient srh and shear. Wind profiles leave a lot to be desired though at this point You have really unrealistic standards for "wind profiles," in this part of the country no less. Link to comment Share on other sites More sharing options...
Hoosier Posted February 26, 2017 Share Posted February 26, 2017 1 hour ago, cyclone77 said: NAM products would bring the tor threat up into southeast Iowa, and along and south of the I-80 corridor in Illinois on Tuesday. Surface low is deep enough to keep the surface winds backed beneath some pretty impressive mid-levels. Some forecast soundings are showing over 80kts of shear from the LCL to the EL. Great wind shear in the lower 1km as well. If the NAM products are on to something the slight will need to be lifted further north into these areas. I would expect it to come north on later outlooks, barring some significant change in the setup. Link to comment Share on other sites More sharing options...
andyhb Posted February 26, 2017 Author Share Posted February 26, 2017 2 hours ago, janetjanet998 said: 12z GFS stronger then 00z and seems to break CAP tuesday afternoon over AR area while NAM holds Might also be an issue regarding the BMJ convective scheme as well. See this a fair amount of time with the NAM and its derivative products (i.e. basically has 0 CIN but keeps the cap intact due to the fact that it requires moistening of the mid levels to resolve initiation). I will say the SREF's signal is rather benign for now, which likely results from a lack of convective precip being resolved given the potential parameter space. If there are any surface based storms remaining late Tuesday night into Wednesday morning, those could get interesting in a hurry. Link to comment Share on other sites More sharing options...
andyhb Posted February 26, 2017 Author Share Posted February 26, 2017 For example, here we see that the NAM is putting out some pretty decent vertical velocities (negative values being upward motion given the fact that it is dPa/s) indicating forcing for ascent vs. subsidence across the warm sector at 00z Wednesday, so you probably could expect initiation somewhere in there. GFS is even more pronounced in this regard. Link to comment Share on other sites More sharing options...
LouWX Posted February 26, 2017 Share Posted February 26, 2017 Euro model had nice LL backing, ~1000 Joules and streaks of convective precip all across the Ohio River corridor 0-18Z Wednesday. Quite interesting to say the least. Link to comment Share on other sites More sharing options...
buckeye Posted February 26, 2017 Share Posted February 26, 2017 13 minutes ago, LouWX said: Euro model had nice LL backing, ~1000 Joules and streaks of convective precip all across the Ohio River corridor 0-18Z Wednesday. Quite interesting to say the least. LouWX...!?!?! as in THE Louwxman??? Where you been hiding? Link to comment Share on other sites More sharing options...
Stebo Posted February 26, 2017 Share Posted February 26, 2017 3 minutes ago, buckeye said: LouWX...!?!?! as in THE Louwxman??? Where you been hiding? I don't believe they are the same. Link to comment Share on other sites More sharing options...
LouWX Posted February 26, 2017 Share Posted February 26, 2017 Busy life !! And I only really post for severe wx -- I'm no fan of winter. Maybe you are thinking of someone else! Link to comment Share on other sites More sharing options...
buckeye Posted February 26, 2017 Share Posted February 26, 2017 16 minutes ago, LouWX said: Busy life !! And I only really post for severe wx -- I'm no fan of winter. Maybe you are thinking of someone else! There was a guy who posted regularly years ago, especially back on EUSWX. His screen name was Louwxman and I believe he was also an OCM in Louisville. I guess just a coincidence. Link to comment Share on other sites More sharing options...
janetjanet998 Posted February 26, 2017 Share Posted February 26, 2017 18Z NAM continues to hold CAP tuesday evening I also assume its overdoing dewpoints up to 68-70 over AR A powderkeg after dark with LI's -12 and 2800 CAPE Link to comment Share on other sites More sharing options...
janetjanet998 Posted February 26, 2017 Share Posted February 26, 2017 18z NAM also has a 90 KT 700mb jet max punching into the OH river valley at 15z weds(yes 700mb) Link to comment Share on other sites More sharing options...
Chinook Posted February 26, 2017 Share Posted February 26, 2017 I am not sure how much this affects the severe weather scenario. The NAM has the surface low tracking from Hannibal MO to Toledo OH, and intensifying. From a look at the global models, it seems this surface low will be farther north in MI and WI. The GFS has the low near Sault Ste. Marie and Sudbury ON at the period of interest. The Euro is in WI/MI but not that far north. So the NAM might have somewhat incorrect low-level winds. I certainly don't want to discount any severe weather threat, because those 60-70 kt 0-6km shear values have resulted in tornadoes a bunch of times! Link to comment Share on other sites More sharing options...
Quincy Posted February 26, 2017 Share Posted February 26, 2017 With some issues WRT placement and timing and key features, it will probably be another day or so before we get more clarity on Wednesday's threat. (Tuesday looks like a cap bust in this sub-forum) I do see increasing potential for overnight/morning warm sector storms moving into the Ohio Valley by early Wednesday, followed by a muddled/messy second round of storms later in the day. Perhaps a Friday do-over with a somewhat more favorable setup? Link to comment Share on other sites More sharing options...
Hoosier Posted February 26, 2017 Share Posted February 26, 2017 NAM is still hitting on the slower trailing surface low. Question is whether to buy it. Link to comment Share on other sites More sharing options...
bdgwx Posted February 26, 2017 Share Posted February 26, 2017 Yeah, the NAM is looking pretty potent, but is quite a bit different from the GFS and Euro. Link to comment Share on other sites More sharing options...
Indystorm Posted February 26, 2017 Share Posted February 26, 2017 Which model had better verification last Friday? Link to comment Share on other sites More sharing options...
andyhb Posted February 26, 2017 Author Share Posted February 26, 2017 1 minute ago, Indystorm said: Which model had better verification last Friday? Enhanced mixing given the temperatures overperforming meant they were all off to some degree thermodynamically. As far as the wind fields were concerned, probably something closer to the Euro. Didn't help that the surface low wasn't as strong as guidance had suggested. Link to comment Share on other sites More sharing options...
Jim Martin Posted February 27, 2017 Share Posted February 27, 2017 This afternoon's run of the SREF, with the Significant Tornado Ingredients.... Link to comment Share on other sites More sharing options...
Indystorm Posted February 27, 2017 Share Posted February 27, 2017 And 72 hrs at 18Z NAM is hopefully overdoing things because central IN parameters are favorable for strong tornadoes. As has been mentioned the timing of that frontal system will be a key factor regarding model wars. Link to comment Share on other sites More sharing options...
Stebo Posted February 27, 2017 Share Posted February 27, 2017 If things remain uncapped overnight Tuesday night into Wednesday, the NAM really paints an extremely volatile picture. The amount of low level shear in the first km is very damn good with exceptional speed shear above that layer and very favorable lapse rates. Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2017 Share Posted February 27, 2017 4 minutes ago, Stebo said: If things remain uncapped overnight Tuesday night into Wednesday, the NAM really paints an extremely volatile picture. The amount of low level shear in the first km is very damn good with exceptional speed shear above that layer and very favorable lapse rates. Decent environment progged fairly far north too. This is a bit southwest of South Bend at 6z Wednesday. Link to comment Share on other sites More sharing options...
NTXYankee Posted February 27, 2017 Share Posted February 27, 2017 0z NAM still holding on to it's slower low track Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2017 Share Posted February 27, 2017 Still have significant differences between the NAM and GFS. Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2017 Share Posted February 27, 2017 The NAM is still on the slower side to initiate Tuesday, but looking at various models, it looks like there's a shot at redevelopment/initiation by late afternoon. Link to comment Share on other sites More sharing options...
OHweather Posted February 27, 2017 Share Posted February 27, 2017 With another EML (I feel like we had 0 good EMLs the last 2 seasons, at least it felt that way), what should be a somewhat better moisture return due to not having a cut-off low spinning near FL, and a 100kt 500mb jet expected to intersect the warm sector, you'd have to think there's decent potential for Tuesday into Wednesday. The differences among the models regarding timing/track of the low (or in the NAM's case if a second low develops on Wednesday over the northern Ohio Valley) make it hard to pin down the location and magnitude of the threat. As was the case with the last event with no snow cover I don't see why some threat wouldn't get all the way up to the low track, and with the models trying to hint at impressive wind fields moving across the Ohio Valley/southern Lakes Tuesday night into Wednesday morning the prospects of an overnight event seem interesting...with dews possibly in the upper 50s to near 60 and steep ML lapse rates some instability should be maintained overnight, especially if we get a 60-70kt 850mb jet returning moisture into the area Tuesday night. The 3k/4k NAMs would be damn interesting, but there's still a lot of time to trend towards a somewhat faster/flatter solution. Link to comment Share on other sites More sharing options...
Chicago Storm Posted February 27, 2017 Share Posted February 27, 2017 The NAM is obviously the best case scenario if you're looking for severe wx at this point. The ECMWF and GFS (to lesser degree, also show some potential.The question is, is the NAM being the NAM and over-amped with the wave, or is it onto something? Given how this season has gone, the former is more likely.Definitely a bit more intrigued with this potential event than I was with Friday's event though. Link to comment Share on other sites More sharing options...
janetjanet998 Posted February 27, 2017 Share Posted February 27, 2017 12z NAM still shooting blanks with any convection over AR moving NE Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2017 Share Posted February 27, 2017 NAM products may be unrealistically deepening the surface low Tuesday evening/Wednesday morning. Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2017 Share Posted February 27, 2017 In any case, it looks like some severe threat may be maintained well into the overnight hours on Tuesday night/Wednesday morning, at least into the Ohio Valley and possibly northward toward the I-80 corridor, as low level warm air/moisture advection tries to offset nocturnal cooling. Link to comment Share on other sites More sharing options...
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