IllinoisWedges Posted November 2, 2017 Share Posted November 2, 2017 I believe there is enough support for us to make a separate thread on this topic instead of using the general severe talk thread. SPC went Day 4 30% mentioning all hazards and supercells as the dominant storm mode. Euro and GFS both have a pretty beefy setup, especially along the warm front, while the NAM is doing NAM things with a slower, more laid back approach. Link to comment Share on other sites More sharing options...
Radtechwxman Posted November 2, 2017 Share Posted November 2, 2017 This looks eerily similar to how 11-17-13 looked a few days out. Not saying this will reach that calibur but def has the grounds for something significant Link to comment Share on other sites More sharing options...
Indystorm Posted November 2, 2017 Share Posted November 2, 2017 Anytime I see two strong diverging jet streams at upper levels with a progged 50 knot LLJ in the forecast, with all other parameters being favorable, my concern is really heightened. 59/57 here now this morning with forecast highs today in the mid 60's to prime the pump with the first system and only a slight cool down before warming up once again. Link to comment Share on other sites More sharing options...
OHweather Posted November 2, 2017 Share Posted November 2, 2017 An EML, good agreement on low to mid 60s dew points, and November dynamics/shear. There's still a lot of time to work out the finer details but I can definitely see why the SPC already has a 30% risk. Link to comment Share on other sites More sharing options...
CheeselandSkies Posted November 2, 2017 Share Posted November 2, 2017 Odd to see the NAM lowballing the northward extent of the CAPE compared to the GFS. I'm used to it being the other way around. Link to comment Share on other sites More sharing options...
tornado_junkies Posted November 2, 2017 Share Posted November 2, 2017 The NAM at this range lol... Link to comment Share on other sites More sharing options...
CheeselandSkies Posted November 2, 2017 Share Posted November 2, 2017 Yeah 12Z NAM is still meh. Used to the NAM (although more so the high res/3k version) being the one that goes excessively great gangbusters with severe parameters, although that seems more like a summer thing where it goes across the board PDS TOR on massive CAPE. Link to comment Share on other sites More sharing options...
Hoosier Posted November 2, 2017 Share Posted November 2, 2017 3 hours ago, StormChaser4Life said: This looks eerily similar to how 11-17-13 looked a few days out. Not saying this will reach that calibur but def has the grounds for something significant Similar threat area, yes. 11/17/13 had a much deeper surface low and stronger wind fields, so I don't think we can approach that level/severity without significant changes, but the potential here stacks up well against just about any other November outbreak in the region imo. Link to comment Share on other sites More sharing options...
Hoosier Posted November 2, 2017 Share Posted November 2, 2017 Here's what we had at the surface on 11/17/13. Surface low deepened through the 980s (and eventually into the 970s) as it moved through, which is much deeper than what's progged this time. Some may recall the widespread non-thunderstorm high wind event that occurred on the back side. Link to comment Share on other sites More sharing options...
Chambana Posted November 2, 2017 Share Posted November 2, 2017 The NAM and GFS runs were pretty different this morning. Really intrigued by this setup. Says a lot when SPC has a 30% risk 72 hours out from the event. Link to comment Share on other sites More sharing options...
snowlover2 Posted November 2, 2017 Share Posted November 2, 2017 Wow that 30% area is really close to me. ILN not even hinting at severe in the morning AFD. Hope that would change in the afternoon update. Link to comment Share on other sites More sharing options...
HillsdaleMIWeather Posted November 2, 2017 Share Posted November 2, 2017 12Z GFS still showing a potent event Link to comment Share on other sites More sharing options...
tornado_junkies Posted November 2, 2017 Share Posted November 2, 2017 10 minutes ago, HillsdaleMIWeather said: 12Z GFS still showing a potent event Does anyone else think that GFS may be a tad fast with the evolution of the system? It tends to have a fast bias as far as I'm aware. Link to comment Share on other sites More sharing options...
HillsdaleMIWeather Posted November 2, 2017 Share Posted November 2, 2017 7 minutes ago, tornado_junkies said: Does anyone else think that GFS may be a tad fast with the evolution of the system? It tends to have a fast bias as far as I'm aware. The Euro generally agrees with the evolution as well. NAM is outlier in this case. Link to comment Share on other sites More sharing options...
Radtechwxman Posted November 2, 2017 Share Posted November 2, 2017 42 minutes ago, Hoosier said: Similar threat area, yes. 11/17/13 had a much deeper surface low and stronger wind fields, so I don't think we can approach that level/severity without significant changes, but the potential here stacks up well against just about any other November outbreak in the region imo. Yea I totally agree. That's like a benchmark now for Fall outbreaks. Besides the Veterans Day outbreak. I don't think we will see a tornado outbreak of that scale due to the factors you listed (weaker sfc low and not as strong wind fields). But like you said the parameters for this are significant for this time of year. A localized tornado event, most likely near wf, is def possible. Prolly will see a long squall line develop on cf and maybe some warm sector supercells depending on if eml can be overcome. Despite the lack of significant turning in the low levels and not as high low level shear as 11-17, the cap may help keep some storms discrete esp given that forcing won't be extreme ahead of cf Link to comment Share on other sites More sharing options...
tornado_junkies Posted November 2, 2017 Share Posted November 2, 2017 8 minutes ago, HillsdaleMIWeather said: The Euro generally agrees with the evolution as well. NAM is outlier in this case. Good point. Looking forward to seeing the 12z version of the ECM. 5 minutes ago, StormChaser4Life said: Yea I totally agree. That's like a benchmark now for Fall outbreaks. Besides the Veterans Day outbreak. I don't think we will see a tornado outbreak of that scale due to the factors you listed (weaker sfc low and not as strong wind fields). But like you said the parameters for this are significant for this time of year. A localized tornado event, most likely near wf, is def possible. Prolly will see a long squall line develop on cf and maybe some warm sector supercells depending on if eml can be overcome. Despite the lack of significant turning in the low levels and not as high low level shear as 11-17, the cap may help keep some storms discrete esp given that forcing won't be extreme ahead of cf Well said. The warm front will certainly be a key to this event IMO. I can see the warm sector wind profiles veering quickly if both the GFS and ECM were to verify. A localized significant tornado event certainly isn't out of the question if some key factors were to come together. At 4 days out, the general consensus is high cape for this time of year with a combination of more than adequate shear profiles will result in an active fall severe weather event. Link to comment Share on other sites More sharing options...
snowlover2 Posted November 2, 2017 Share Posted November 2, 2017 5 hours ago, StormChaser4Life said: This looks eerily similar to how 11-17-13 looked a few days out. Not saying this will reach that calibur but def has the grounds for something significant 1 hour ago, Hoosier said: Similar threat area, yes. 11/17/13 had a much deeper surface low and stronger wind fields, so I don't think we can approach that level/severity without significant changes, but the potential here stacks up well against just about any other November outbreak in the region imo. 58 minutes ago, Hoosier said: Here's what we had at the surface on 11/17/13. Surface low deepened through the 980s (and eventually into the 970s) as it moved through, which is much deeper than what's progged this time. Some may recall the widespread non-thunderstorm high wind event that occurred on the back side. Since 11/17/13 is being brought up, I thought i'd show the storm report map from that day. Probably won't get that bad but just an idea from what happened that day. Link to comment Share on other sites More sharing options...
Hoosier Posted November 2, 2017 Share Posted November 2, 2017 IWX made a good point about the forcing being less than what's typical at this time of year. It's true... look at almost any significant November outbreak in the region (the aforementioned 11/17/13, 11/15/05, 11/5/05, 11/10/02, 11/10/98, 11/22/92, 11/15/89, etc.) and they had better height falls/deeper troughs. So I could see a scenario in which there's resistance to transition away from supercell mode. Link to comment Share on other sites More sharing options...
Chambana Posted November 2, 2017 Share Posted November 2, 2017 Going to need a lot more clearing than what’s currently modeled as well. Link to comment Share on other sites More sharing options...
Hoosier Posted November 2, 2017 Share Posted November 2, 2017 1 minute ago, Chambana said: Going to need a lot more clearing than what’s currently modeled as well. I actually don't think this is as important, given the steep mid level lapse rates being progged. I look at any clearing in this setup as a bonus. I think it's game on as long as overcast isn't restrictive enough to keep temps cooler than low-mid 60s. Link to comment Share on other sites More sharing options...
Stebo Posted November 2, 2017 Share Posted November 2, 2017 12 minutes ago, Hoosier said: IWX made a good point about the forcing being less than what's typical at this time of year. It's true... look at almost any significant November outbreak in the region (the aforementioned 11/17/13, 11/15/05, 11/5/05, 11/10/02, 11/10/98, 11/22/92, 11/15/89, etc.) and they had better height falls/deeper troughs. So I could see a scenario in which there's resistance to transition away from supercell mode. It is a very delicate balance though, because you do need some forcing for initiation too, currently as modeled there is enough forcing and lift to get things going. Link to comment Share on other sites More sharing options...
nwburbschaser Posted November 2, 2017 Share Posted November 2, 2017 11 minutes ago, Chambana said: Going to need a lot more clearing than what’s currently modeled as well. I agree with Hoosier here and don't think this will be a huge issue. Also, modeled cloud cover at this point isn't overly reliable. Since we are talking about 11/17, that was a day that ended up clearing out a bit more than originally thought. It wasn't necessary, but it certainly aided in even better instability. Link to comment Share on other sites More sharing options...
Stebo Posted November 2, 2017 Share Posted November 2, 2017 Even with the NAM severely lowballing the instability at this junction it still presents us with a few things of interest. Even at face value it is not bad, combine that with a factor that is important, and that is the low level wind field. It is showing much better low level shear unlike the GFS. For example: Link to comment Share on other sites More sharing options...
hlcater Posted November 2, 2017 Share Posted November 2, 2017 3 minutes ago, Stebo said: Even with the NAM severely lowballing the instability at this junction it still presents us with a few things of interest. Even at face value it is not bad, combine that with a factor that is important, and that is the low level wind field. It is showing much better low level shear unlike the GFS. For example: The first and second soundings are the same. Thought I'd let you know that. Link to comment Share on other sites More sharing options...
Stebo Posted November 2, 2017 Share Posted November 2, 2017 Just now, NWLinnCountyIA said: The first and second soundings are the same. Thought I'd let you know that. Weird, I only posted 2, must have posted 1st one twice. Link to comment Share on other sites More sharing options...
Stebo Posted November 2, 2017 Share Posted November 2, 2017 23 minutes ago, Chambana said: Going to need a lot more clearing than what’s currently modeled as well. Not seeing much of the way in clouds other than low level clouds and those can be eroded over time. When checking the 700mb RH, things look very good for limiting mid level clouds. Link to comment Share on other sites More sharing options...
hlcater Posted November 2, 2017 Share Posted November 2, 2017 7 minutes ago, Stebo said: Weird, I only posted 2, must have posted 1st one twice. Yea I only see the 2 now. Problem must've fixed itself. I'm also gonna get a GFS sounding for comparison. Taken near Peoria. The lack of low level curvature is extremely evident here, compared to the NAM, and even then, not a bad sounding. Link to comment Share on other sites More sharing options...
tornado_junkies Posted November 2, 2017 Share Posted November 2, 2017 2 minutes ago, Stebo said: Weird, I only posted 2, must have posted 1st one twice. Trying to pull a fast one there Stebo... Link to comment Share on other sites More sharing options...
Stebo Posted November 2, 2017 Share Posted November 2, 2017 Just now, tornado_junkies said: Trying to pull a fast one there Stebo... Sure random poster... Link to comment Share on other sites More sharing options...
geddyweather Posted November 2, 2017 Share Posted November 2, 2017 7 minutes ago, nwburbschaser said: I agree with Hoosier here and don't think this will be a huge issue. Also, modeled cloud cover at this point isn't overly reliable. Since we are talking about 11/17, that was a day that ended up clearing out a bit more than originally thought. It wasn't necessary, but it certainly aided in even better instability. A day that I can think of where there was total overcast but still produced a fruitful outbreak was 8/24/2016. Total overcast in most locations but temps in the upper 70s/low 80s, dews the 60/70s, good SRH, and ample deep layer vertical shear made for a very active day. Though not exactly applicable for November in terms of certain conditions, this is one day that comes to my mind where clearing played little to no role in the events that followed. Link to comment Share on other sites More sharing options...
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