November 5th, 2017 Severe Weather Event

[Stebo]

6 minutes ago, RCNYILWX said:

A majority of 12z EPS members shifted a bit weaker and south with the surface low vs. the 00z run. Still a ways to go, but considering shift on operational Euro as well, not the trends you'd want to see for a more substantial event, particularly with northward extent in Illinois.

Yeah I noticed this, have to see if it is an aberration or a trend. For a lot of them to jump all at once is kind of a red flag for me.

[geddyweather]

14 minutes ago, Stebo said:

Yeah I noticed this, have to see if it is an aberration or a trend. For a lot of them to jump all at once is kind of a red flag for me.

Perhaps this is one of the reasons IWX and ILN (to a lesser extent) have sounded less than enthused on the last WFD? A weaker south move would hamper some of the potential for sure.

[Stebo]

Just now, geddyweather said:

Perhaps this is one of the reasons IWX and ILN (to a lesser extent) have sounded less than enthused on the last WFD? A weaker south move would hamper some of the potential for sure.

In this case though it would put their CWAs in a better position to get something, where as a northerly solution would limit what they get especially ILN.

[geddyweather]

15 minutes ago, Stebo said:

In this case though it would put their CWAs in a better position to get something, where as a northerly solution would limit what they get especially ILN.

That's how it seemed to me too while looking at it. Hmmm. I suppose each new 24 hours will provide some more clarity for us. As of now the southward shift in the Euro is definitely something to keep track of.

[tornadohunter]

Van wert Ohio. That is all.

[HillsdaleMIWeather]

18Z NAM looks to be trending towards the other models, has the higher instability over a larger area

[Stebo]

5 minutes ago, HillsdaleMIWeather said:

18Z NAM looks to be trending towards the other models, has the higher instability over a larger area

Did however trend closer to the Euro with the low track too.

[andyhb]

27 minutes ago, tornadohunter said:

Van wert Ohio. That is all.

This is relevant how beyond it being November and in the Great Lakes?

[tornadohunter]

1 minute ago, andyhb said:

This is relevant how beyond it being November and in the Great Lakes?

It's a tornado prone area and parameters and pretty good there. 

[andyhb]

Just now, tornadohunter said:

It's a tornado prone area and parameters and pretty good there. 

Shear isn't anywhere near where it was in Ohio that day.

[tornado_junkies]

18Z GFS FWIW is much less than impressive

[andyhb]

When it's November and you can't get a trough to dig south of Minnesota...

[Stebo]

2 minutes ago, tornado_junkies said:

18Z GFS FWIW is much less than impressive

It is comparable to the previous runs, if anything it is a bit stronger with LLJ across IN. Not sure what you are looking at.

[tornadohunter]

3 minutes ago, andyhb said:

Shear isn't anywhere near where it was in Ohio that day.

I should have said topographically favorable. Strong believer in topo having a key role in tornadogensis when parameters are decent but less than ideal. I.E. Colorado is a prime example

[HillsdaleMIWeather]

1 minute ago, Stebo said:

It is comparable to the previous runs, if anything it is a bit stronger with LLJ across IN. Not sure what you are looking at.

He was probably looking at the raw supercell composite numbers 

[andyhb]

Just now, tornadohunter said:

I should have said topographically favorable. Strong believer in topo having a key role in tornadogensis when parameters are decent but less than ideal. I.E. Colorado is a prime example

What?

Comparing Colorado and western Ohio as far as topographic influence doesn't make much sense.

[Jim Martin]

[Stebo]

1 minute ago, HillsdaleMIWeather said:

He was probably looking at the raw supercell composite numbers 

Yeah I don't look at one alphabet soup index and say the potential is good or bad. That is just not worth posting at that point.

[Jim Martin]

Two dates, in a sense, pop up in my mind about Sunday.

- March 2, 2012

- November 17, 2013.

[andyhb]

3 minutes ago, Jim Martin said:

Two dates, in a sense, pop up in my mind about Sunday.

- March 2, 2012

- November 17, 2013.

I don't see the potential reaching anywhere near either of those.

Both of those events had very vigorous surface lows, deepening throughout the day to maximize near-surface pressure falls, back the surface winds and strengthen the low level jet considerably. That is not the case here. In general, both upper level troughs associated with those events were significantly stronger than this one is as well (100+ kt 500 mb maxes, pronounced cyclonic vorticity maxima, etc).

[Jim Martin]

Just now, andyhb said:

I don't see the potential reaching anywhere near either of those.

Ah.

[tornado_junkies]

8 minutes ago, Stebo said:

It is comparable to the previous runs, if anything it is a bit stronger with LLJ across IN. Not sure what you are looking at.

Probably would help if i changed it from 12z to 18z...

[Radtechwxman]

1 hour ago, andyhb said:

I don't see the potential reaching anywhere near either of those.

Both of those events had very vigorous surface lows, deepening throughout the day to maximize near-surface pressure falls, back the surface winds and strengthen the low level jet considerably. That is not the case here. In general, both upper level troughs associated with those events were significantly stronger than this one is as well (100+ kt 500 mb maxes, pronounced cyclonic vorticity maxima, etc).

I couldn't agree more. Yes this has good parameters for a Nov setup, esp this north. But for a classic tornado outbreak like those days you must have a well developed sfc low preferably deepening to maximize backed winds and llj response like you stated. This trough is more zonal which isn't helping to really invigorate intense cyclogenesis. Sun could still be a very active severe wx day and tornadoes are possible, but a tornado outbreak doesn't seem likely at this time. Curious to see though how this atypical Fall EML impacts storm mode. However, with limited height falls and pressure falls not sure we will see storms break out well into warm sector vs closer to the front. Def got my eye on it and will likely chase locally

[nwohweather]

1 hour ago, andyhb said:

Shear isn't anywhere near where it was in Ohio that day.

Ha actually on big severe weather days that's almost always my go to chase spot. It's not the most scientific thing ever, but for some reason that spot is a tornado magnet. Plus you have US-127 to move north/south, US-224 to take you towards Findlay, or US-30 to move due east/west. Plus pure flat farmland

[Quincy]

Another potential issue here appears to be lapse rates in the 0-3km layer. Yes, mid to upper level lapse rates look very favorable, but forecast soundings show an inversion in the 850-750mb layer across Indiana and surrounding areas Sunday afternoon. A modest capping inversion could be a net positive in terms of discrete nature of storms, however, if the cap is too substantial, there won't be surface-based convection. 

The KIND forecast soundings at 21z Sunday from both the GFS and NAM show a sizable cap and meager 0-3km lapse rates of less than 6 C/km. Even at 00z, the low level lapse rates remain marginal and suggest there may be a significant lack of surface-based convection in the warm sector. Soundings farther west and north show similar issues. The NAM's forecast cap is actually more substantial than the GFS. (18z 11/2)

It's certainly not a typical November setup. Cool air aloft contributes to steep 700-500mb lapse rates (>7.5 C/km), however unseasonably warm air in the 800-750mb layer creates an environment with marginal boundary layer instability and resultant surface-based convective inhibition. The 16z ILX sounding on 11/17/13 sampled 7.6 C/km 0-3km lapse rates. The only other thing to note here is that the warm frontal zone may be more favorable for tornadogenesis this time around than it was on 11/17/13, when the warm front was all the way up to northern Lower Michigan and featured poor instability and marginal boundary layer moisture in comparison to this November's potential event.

The issues about cloud-cover don't seem major either. Some clouds can actually work to keep LCLs down a bit and with relatively strong wind fields in place, kinematics become more important than thermodynamics. CAPEs were only around 1000 J/kg, generally, for 11/17/13. The environmental average mean MLCAPE for tornadoes in the Indiana area is only in the ballpark of 500-1000 J/kg.

For what it's worth, CIPS does rank 11/17/13 in the top 10 (#9) for analog matches to Sunday, but only 3/15 (20%) of analogs show a tornado outbreak in the Ohio Valley/Midwest vicinity.

[HillsdaleMIWeather]

27 minutes ago, Quincy said:

Another potential issue here appears to be lapse rates in the 0-3km layer. Yes, mid to upper level lapse rates look very favorable, but forecast soundings show an inversion in the 850-750mb layer across Indiana and surrounding areas Sunday afternoon. A modest capping inversion could be a net positive in terms of discrete nature of storms, however, if the cap is too substantial, there won't be surface-based convection. 

The KIND forecast soundings at 21z Sunday from both the GFS and NAM show a sizable cap and meager 0-3km lapse rates of less than 6 C/km. Even at 00z, the low level lapse rates remain marginal and suggest there may be a significant lack of surface-based convection in the warm sector. Soundings farther west and north show similar issues. The NAM's forecast cap is actually more substantial than the GFS. (18z 11/2)

It's certainly not a typical November setup. Cool air aloft contributes to steep 700-500mb lapse rates (>7.5 C/km), however unseasonably warm air in the 800-750mb layer creates an environment with marginal boundary layer instability and resultant surface-based convective inhibition. The 16z ILX sounding on 11/17/13 sampled 7.6 C/km 0-3km lapse rates. The only other thing to note here is that the warm frontal zone may be more favorable for tornadogenesis this time around than it was on 11/17/13, when the warm front was all the way up to northern Lower Michigan and featured poor instability and marginal boundary layer moisture in comparison to this November's potential event.

The issues about cloud-cover don't seem major either. Some clouds can actually work to keep LCLs down a bit and with relatively strong wind fields in place, kinematics become more important than thermodynamics. CAPEs were only around 1000 J/kg, generally, for 11/17/13. The environmental average mean MLCAPE for tornadoes in the Indiana area is only in the ballpark of 500-1000 J/kg.

For what it's worth, CIPS does rank 11/17/13 in the top 10 (#9) for analog matches to Sunday, but only 3/15 (20%) of analogs show a tornado outbreak in the Ohio Valley/Midwest vicinity.

I think whatever happens, this will be a good case study to look at afterwards, since this is a pretty unique setup.

[Indystorm]

To be fair I don't think any of us are expecting a tornado outbreak.  IND forecast has only mentioned chance of isolated tornadoes, although I am somewhat concerned that SPC this Thursday at least was thinking that mode might possibly remain supercellular.  Will have to see additional model runs as we get closer as usual.

[OHweather]

34 minutes ago, Quincy said:

Another potential issue here appears to be lapse rates in the 0-3km layer. Yes, mid to upper level lapse rates look very favorable, but forecast soundings show an inversion in the 850-750mb layer across Indiana and surrounding areas Sunday afternoon. A modest capping inversion could be a net positive in terms of discrete nature of storms, however, if the cap is too substantial, there won't be surface-based convection. 

The KIND forecast soundings at 21z Sunday from both the GFS and NAM show a sizable cap and meager 0-3km lapse rates of less than 6 C/km. Even at 00z, the low level lapse rates remain marginal and suggest there may be a significant lack of surface-based convection in the warm sector. Soundings farther west and north show similar issues. The NAM's forecast cap is actually more substantial than the GFS. (18z 11/2)

It's certainly not a typical November setup. Cool air aloft contributes to steep 700-500mb lapse rates (>7.5 C/km), however unseasonably warm air in the 800-750mb layer creates an environment with marginal boundary layer instability and resultant surface-based convective inhibition. The 16z ILX sounding on 11/17/13 sampled 7.6 C/km 0-3km lapse rates. The only other thing to note here is that the warm frontal zone may be more favorable for tornadogenesis this time around than it was on 11/17/13, when the warm front was all the way up to northern Lower Michigan and featured poor instability and marginal boundary layer moisture in comparison to this November's potential event.

The issues about cloud-cover don't seem major either. Some clouds can actually work to keep LCLs down a bit and with relatively strong wind fields in place, kinematics become more important than thermodynamics. CAPEs were only around 1000 J/kg, generally, for 11/17/13. The environmental average mean MLCAPE for tornadoes in the Indiana area is only in the ballpark of 500-1000 J/kg.

For what it's worth, CIPS does rank 11/17/13 in the top 10 (#9) for analog matches to Sunday, but only 3/15 (20%) of analogs show a tornado outbreak in the Ohio Valley/Midwest vicinity.

A little cap can be good, as it can limit weaker convection from firing too early and can keep storms that do fire discrete for a longer period of time.  Obviously, too much can completely kill a threat.  The models generally do have storms firing with the cold front itself, so it's possible (if not likely) the frontal circulation is enough to lift parcels above the cap...but that would certainly limit the tornado threat to more of a brief/spinup type with any forced line segments along the cold front near or after dark. 

I think instability or lack thereof won't be an issue, as the current projections for instability are plenty good when compared to other outbreaks in this region in November.  Veered surface winds area concern with a lack of a progged deep surface low.  There's decent UL divergence over the Great Lakes Sunday afternoon/evening, but the jet streaks aren't the strongest and as has been mentioned height falls aren't impressive given the time of year.  That said, the models still generate enough SRH when combined with low LCLs for a decent tornado threat, but I can't recall any big tornado events this time of year with such a weak surface low.

I have to think that given the seasonably strong instability and more than adequate shear that it'll be hard to avoid some severe weather.  Ingredients for a big tornado outbreak may be missing...namely good evidence for discrete warm sector convection and somewhat veered surface winds.  With such a strong LLJ there could be a half decent coverage of wind reports either way.  I also wonder if elevated convection can fire along the warm front with a hail threat as the EML advects in. 

[Hoosier]

22 minutes ago, Indystorm said:

To be fair I don't think any of us are expecting a tornado outbreak.  IND forecast has only mentioned chance of isolated tornadoes, although I am somewhat concerned that SPC this Thursday at least was thinking that mode might possibly remain supercellular.  Will have to see additional model runs as we get closer as usual.

Thing is, what is an "outbreak" anyway?  I think the old accepted definition was >5 tornadoes within x amount of time, but that seems outdated with increased reporting these days.  A large tornado outbreak looks unlikely, but a smaller one may be possible.

[Hoosier]

Surface low strength looks a bit like 11/22/2010.  However, low level moisture looks better for this setup.