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Hoosier

2017 Short/Medium Range Severe Thread

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3 minutes ago, Hoosier said:

Here's the 12z Euro SBCAPE.  Impressive northward extent for time of year.

us_model-en-087-0_modez_2017103112_129_511_255.thumb.png.a499ec936a533ab50379abdb3bcaa6da.png

I haven't played around with that site much yet, do they have lapse rates on there, would be interested to see if they are comparable to the GFS.

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4 minutes ago, Stebo said:

I haven't played around with that site much yet, do they have lapse rates on there, would be interested to see if they are comparable to the GFS.

No

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1 minute ago, IllinoisWedges said:

Here's 12z Sunday.. 00z is a mess because of convection. 

ecmwf_700500lapse_120_nc.jpg

ecmwf_850500lapse_120_nc.jpg

Still can decipher from these images that a nice EML slides ENE into the area during the day on Sunday.

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Yada yada yada pretty colors. Andy Berrington did a good job going in depth on Twitter about Sunday. Big EML for this time of year coming. 00z Euro has a bit better lapse rates at 12z SUN.

 

EDIT: SPC added a big 15% for IL/SE WI/IN/and most of S-C MI. 

 

Quote
Substantial height falls will occur across the Plains and into the
   Midwest on Sun/D5 with parallel shortwave troughs. The strongest
   wave will move across the northern Plains, with the secondary one
   across the central Plains into the Midwest. At the surface, a cold
   front will extend roughly from MI into MO and OK, with the
   possibility of mid 60s dewpoints ahead of it and MUCAPE values in
   excess of 1500 J/kg. This may result in severe thunderstorms from IL
   and southern WI across lower MI and IN Sunday and Sunday night. The
   main threat will be large hail and damaging winds with long
   hodographs and steep lapse rates aloft. Both supercell and linear
   storm modes will be possible.

us_model-en-087-0_modez_2017110100_117_511_255.png

day5prob (1).gif

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Figured I'd post some of those thoughts here as we now have a 15% D5.

Firstly, the instability being depicted here is certainly upper echelon for this region this time of year. Don't see a lot of setups with widespread 1500-2000+ CAPE this far north in November. Unseasonably high moisture (mid 60s dews with deep moisture to at least 850 mb) and steep mid level lapse rates associated with a well-developed EML (7.5-8+ C/km) are the culprits. As has been repeated ad nauseam in these threads over the years, in the cold season, this is what you are looking for first and foremost. Moderate capping may also tend to keep cells isolated for a time since the upper feature that would actually initiate storms in this case (the secondary shortwave trough mentioned in the D4-8 outlook) is rather subtle.

Secondly, this setup has one of the telltale synoptic looks of a Great Lakes severe event with a potent shortwave trough emerging and shooting ENE out of a larger scale western trough, while a trailing wave remains on the West Coast. That said, in this case it is a bit further north, which may affect the way the low level mass fields behave (perhaps less backing since the stronger pressure falls near the surface may remain further north).

With that said, a wild card may be if we can get a more defined secondary surface low to form along the surface trough extending southward from Ontario. That would open the door for perhaps a more southerly component to the surface winds and perhaps a stronger low level jet. The deep layer shear certainly is plentiful as is with 50-70 kts across most of the region, so there should certainly be some severe weather, but the question is whether there will be elevated tornadic potential. Right now I would lean away from that, but it wouldn't take a whole lot to change that idea.

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Sunday is very intriguing for severe. Could be some tor potential, especially if we can get a slightly deeper SLP solution.

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Most of the soundings I've pulled, both 18z and 00z, have a considerable EML creating quite a bit of CINH. This leads to me having concerns about capping and whether this will be able to be broken or not. 

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7 hours ago, andyhb said:

Figured I'd post some of those thoughts here as we now have a 15% D5.

Firstly, the instability being depicted here is certainly upper echelon for this region this time of year. Don't see a lot of setups with widespread 1500-2000+ CAPE this far north in November. Unseasonably high moisture (mid 60s dews with deep moisture to at least 850 mb) and steep mid level lapse rates associated with a well-developed EML (7.5-8+ C/km) are the culprits. As has been repeated ad nauseam in these threads over the years, in the cold season, this is what you are looking for first and foremost. Moderate capping may also tend to keep cells isolated for a time since the upper feature that would actually initiate storms in this case (the secondary shortwave trough mentioned in the D4-8 outlook) is rather subtle.

Secondly, this setup has one of the telltale synoptic looks of a Great Lakes severe event with a potent shortwave trough emerging and shooting ENE out of a larger scale western trough, while a trailing wave remains on the West Coast. That said, in this case it is a bit further north, which may affect the way the low level mass fields behave (perhaps less backing since the stronger pressure falls near the surface may remain further north).

With that said, a wild card may be if we can get a more defined secondary surface low to form along the surface trough extending southward from Ontario. That would open the door for perhaps a more southerly component to the surface winds and perhaps a stronger low level jet. The deep layer shear certainly is plentiful as is with 50-70 kts across most of the region, so there should certainly be some severe weather, but the question is whether there will be elevated tornadic potential. Right now I would lean away from that, but it wouldn't take a whole lot to change that idea.

Nice summary.

We should have pretty high confidence in realizing the EML, given a lack of preceding upstream Plains convection.  

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38 minutes ago, Hoosier said:

Nice summary.

We should have pretty high confidence in realizing the EML, given a lack of preceding upstream Plains convection.  

Yeah there are pieces of the puzzle that have a no fail aspect to them for Sunday, this is one of them. Nothing is using that EML until Sunday. Also I would put in strong deep layer shear looks guaranteed at this point.

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10 minutes ago, Stebo said:

Yeah there are pieces of the puzzle that have a no fail aspect to them for Sunday, this is one of them. Nothing is using that EML until Sunday. Also I would put in strong deep layer shear looks guaranteed at this point.

Instability wise, I'd be lying if I said 11/17/13 didn't cross my mind, as far as the magnitude/northward extent of decent destabilization.  That event is a very high bar for fall severe outbreaks though and I'm only talking about one variable, so not suggesting a repeat outcome.

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Just now, Hoosier said:

Instability wise, I'd be lying if I said 11/17/13 didn't cross my mind, as far as the magnitude/northward extent of decent destabilization.  That event is a very high bar for fall severe outbreaks though and I'm only talking about one variable, so not suggesting a repeat outcome.

I will say the instability modeled right now is higher, and the effective bulk shear is comparable as well. The low level shear though isn't, that is part of the puzzle still yet to be resolved. I will say though having a warm front in the area especially for N. IL/IN and S. MI will help the low level wind fields especially once we get into the NAM territory where it can resolve low level winds better than the GFS.

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33 minutes ago, Stebo said:

I will say the instability modeled right now is higher, and the effective bulk shear is comparable as well. The low level shear though isn't, that is part of the puzzle still yet to be resolved. I will say though having a warm front in the area especially for N. IL/IN and S. MI will help the low level wind fields especially once we get into the NAM territory where it can resolve low level winds better than the GFS.

Yeah it does look higher (as currently progged) farther east.  Illinois though had widespread 1000-2000+ J/kg that day, which is similar to what's being progged.   Bottom line, a high end CAPE day for this time of year with questions on evolution and shear (especially low level).  I'd rather have the instability in place and figure out the shear details later compared to the other way around.

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Flipping through the CIPS analogs from the 12z GFS, virtually none of them have instability anywhere close to what's being progged.  There is one event on the list from September (1992) that had somewhat similar instability, but still not quite as far north as this one.

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11 minutes ago, Hoosier said:

Flipping through the CIPS analogs from the 12z GFS, virtually none of them have instability anywhere close to what's being progged.  There is one event on the list from September (1992) that had somewhat similar instability, but still not quite as far north as this one.

Would note that switching domains to Plains and Southeast, 11/22/10 ranks highly on both (#1 on Southeast).  That was memorable in the LOT cwa.

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33 minutes ago, Hoosier said:

Would note that switching domains to Plains and Southeast, 11/22/10 ranks highly on both (#1 on Southeast).  That was memorable in the LOT cwa.

I think I remember that one, at least somewhat. I remember there being an severe weather event across southern and eastern iowa(including tornadoes) and a blizzard ongoing over north and western Iowa. Think could be a different event though, but I'm fairly sure it was this one.

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I will say there is a large number of individual Euro members who are much stronger with the southern low at 18z Sunday, about 20 of the 50 members are 1000mb or stronger, and if you go to 1003mb it is about 28 members. A couple even as strong as 994mb too. If the southern low ends up being more dominant and stronger the ceiling of this event moves much higher because you'd have the backing of the winds at the surface you need.

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5 minutes ago, Stebo said:

I will say there is a large number of individual Euro members who are much stronger with the southern low at 18z Sunday, about 20 of the 50 members are 1000mb or stronger, and if you go to 1003mb it is about 28 members. A couple even as strong as 994mb too. If the southern low ends up being more dominant and stronger the ceiling of this event moves much higher because you'd have the backing of the winds at the surface you need.

That's really the big question.  I think the question is less about whether there will be any severe wx (that looks about as likely as it can from this distance for a Nov event at these latitudes) and more about the magnitude/type.  

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Just now, Hoosier said:

That's really the big question.  I think the question is less about whether there will be any severe wx (that looks about as likely as it can from this distance for a Nov event at these latitudes) and more about the magnitude/type.  

Yep, 100% agree.

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I couldn't agree more with you guys. Synoptically this has the making of a robust Fall severe wx event. The cape and shear being progged is certainly alarming for this time of year. A lot of mesoscale features are yet to be determined. If a stronger sfc low materializes and this strong eml adverts in like pronged, we could def see some discrete to semi discrete supercells ahead of the cf with all severe hazards

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Also noteworthy to see the instability being shown with the 70 degree isotherm remaining south of I-80.  If we overachieve and get low 70s to I-80 (or even farther north) then one can imagine what it will look like.  Looking at 925-850 mb temp profiles, getting 70+ at least to I-80 does look achievable especially with any thinning or breaks in clouds.

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2 minutes ago, Hoosier said:

Also noteworthy to see the instability being shown with the 70 degree isotherm remaining south of I-80.  If we overachieve and get low 70s to I-80 (or even farther north) then one can imagine what it will look like.  Looking at 925-850 mb temp profiles, getting 70+ at least to I-80 does look achievable especially with any thinning or breaks in clouds.

Yeah that is why I'd love to see how this looks once we get into the NAM range of things, as the GFS is going to be light on the temperatures due to climo injected into the model.

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3 minutes ago, Stebo said:

Yeah that is why I'd love to see how this looks once we get into the NAM range of things, as the GFS is going to be light on the temperatures due to climo injected into the model.

Euro had temps like that too though (70 not reaching I-80).  But for reasons mentioned above, certainly could be a bit underdone.

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1 minute ago, Hoosier said:

Euro had temps like that too though (70 not reaching I-80).  But for reasons mentioned above, certainly could be a bit underdone.

Euro did have better dews though which is why its instability is higher.

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3 minutes ago, snowlover2 said:

FWIW 0z NAM at hour 84 (Sunday morning) shows 60's dew points farther south of GFS and i'd assume the Euro. Gets just north of the Ohio River.

 

That's because it's weaker/farther south with the surface low.

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7 minutes ago, Hoosier said:

That's because it's weaker/farther south with the surface low.

Yeah not much to decipher from the NAM at this point.  If anything the inverse NAM principle is in effect. :lmao:

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