April 12 Severe Event

[jpeters3]

5 minutes ago, MUWX said:

One of the Birmingham NWS mets was on twitter saying that the NAM 3KM rarely produced realistic convection in the SE.

This is not a statement with too much scientific support, so I wouldn't lend too much credence to it.

[MUWX]

Just now, jpeters3 said:

This is not a statement with too much scientific support, so I wouldn't lend too much credence to it.

I mean, that may be true, but its a NWS Met in the target area basically saying to discount it. 

[hlcater]

A met for the same NWS office was also saying that the low level moisture will take care of and somewhat compensate for subpar low level lapse rates. While this is certainly true to an extent, I tend to think that low level instability is far more the consequence of low level lapse rates than is on moisture and numerous setups in the past which depended on OWS thunderstorm development suffered for it (5/20 says hi). Furthermore, cold core events with their 50s dews and 7.5*C/km+ LLLRs are the absolute quintessential example of this. Despite the moisture quality being good here, I think if the low level lapse rates decide not to cooperate we may be out of luck and storms may struggle to become surface based in the warm sector. 

[jpeters3]

10 minutes ago, MUWX said:

I mean, that may be true, but its a NWS Met in the target area basically saying to discount it. 

It's just the type of statement that requires a fairly detailed scientific study involving analysis of many events and inter-comparisons between regions to validate (which doesn't exist).  From my experience, even seasoned forecasters can succumb to "forecaster dogma," and this sounds like exactly that.

Not saying the 3km NAM is a great model, but it seems like folks are looking for wishful reasons to excuse it's latest solution.

[MUWX]

Just now, jpeters3 said:

It's just the type of statement that requires a fairly detailed scientific study involving analysis of many events and inter-comparisons between regions to validate (which doesn't exist).  From my experience, even seasoned forecasters can succumb to "forecaster dogma," and this sounds like exactly that.

Not saying the 3km NAM is a great model, but it seems like folks are looking for wishful reasons to excuse it's latest solution.

The opposite can also be true. 

[jpeters3]

7 minutes ago, hlcater said:

A met for the same NWS office was also saying that the low level moisture will take care of and somewhat compensate for subpar low level lapse rates. While this is certainly true to an extent, I tend to think that low level instability is far more the consequence of low level lapse rates than is on moisture and numerous setups in the past which depended on OWS thunderstorm development suffered for it (5/20 says hi). Furthermore, cold core events with their 50s dews and 7.5*C/km+ LLLRs are the absolute quintessential example of this. Despite the moisture quality being good here, I think if the low level lapse rates decide not to cooperate we may be out of luck and storms may struggle to become surface based in the warm sector. 

I agree with this 100%.  Particularly in supercell and tornado environments, MLCAPE seems to be a better outcome discriminator than SBCAPE.  While a few degrees of dew point at the surface may substantially change the lifted parcel path of a SP parcel, the probably won't impact MLCAPE much.  So the low-level lapse rate issue is certainly a potential bust mode.

[jpeters3]

1 minute ago, MUWX said:

The opposite can also be true. 

The opposite of what?

[MUWX]

Just now, jpeters3 said:

The opposite of what?

People trying to find every reason to talk down a risk. 

[Indystorm]

26 minutes ago, jpeters3 said:

Lots of quibbling here over details this far out.  At this point, I think we can all agree that we have the potential for a VERY high end event.  But like many recent would-be high events that did not pan out, the current guidance suite has also shown us a few ways that this could bust.  Maybe it will bust, maybe it won't?  Obviously too early to responsibly make a call either way.

I love the way you and other mets are admitting this could be quite a high end event and then picking all the variables that could mitigate that outcome.  To me that is what good mets do as we approach the day itself.

[jpeters3]

Just now, MUWX said:

People trying to find every reason to talk down a risk. 

You are right about this one, but that is not what is happening here.  The first CAM we get gives us a solution that would certainly qualify as  a "bust."  I don't think this is reason to reduce day 3 to a "see text", but it would be asinine to simply discount this solution based on ill-founded scientific reasoning.

[MUWX]

Just now, jpeters3 said:

You are right about this one, but that is not what is happening here.  The first CAM we get gives us a solution that would certainly qualify as  a "bust."  I don't think this is reason to reduce day 3 to a "see text", but it would be asinine to simply discount this solution based on ill-founded scientific reasoning.

Fair enough, but if we are only going to base forecasting off of things that have been scientifically proven, we aren't going to get super far. I think there is reason to potentially discount the NAM in the short term, based on what the Met who knows the model and the area has to say about it. Doesnt necessarily mean it is wrong, but until other models back it up, that gives me some reason to doubt it. 

[jpeters3]

2 minutes ago, MUWX said:

Fair enough, but if we are only going to base forecasting off of things that have been scientifically proven, we aren't going to get super far. I think there is reason to potentially discount the NAM in the short term, based on what the Met who knows the model and the area has to say about it. Doesnt necessarily mean it is wrong, but until other models back it up, that gives me some reason to doubt it. 

While I don't think it is wrong to doubt this solution (I have my doubts too), I don't think it is good practice to forecast based on dogma and scientifically unfounded principles.

[Indystorm]

Just now, jpeters3 said:

I don't understand this statement at all.  Are we not supposed to mention potential bust mechanisms?  Only the high end scenario?  Your logic doesn't make any sense.

I mean to say that it is the job of good mets in my thinking to acknowledge high end potential and then watch for all the things that could possibly work against that outcome and lower expectations.   On 3/28 the moderate risk outlook for western IL had very high lapse rates, but the anticipated moist low levels did not arrive.  Jonesboro had the moisture.  

[Indystorm]

Just now, jpeters3 said:

Right, so isn't that exactly what is going on here?  I don't understand your criticism of us basically doing exactly what you state in this post.

I am not criticizing.  I am extending a compliment.  Saying that I love the discussion is not meant in a sarcastic way.

[jpeters3]

Just now, Indystorm said:

I am not criticizing.  I am extending a compliment.  Saying that I love the discussion is not meant in a sarcastic way.

I just re-read your original post, and I realize that it was complementary and I mistook it as criticism.  My apologies.  I will delete my offending posts.

I am cranky today, sorry.

[hlcater]

16 minutes ago, jpeters3 said:

I agree with this 100%.  Particularly in supercell and tornado environments, MLCAPE seems to be a better outcome discriminator than SBCAPE.  While a few degrees of dew point at the surface may substantially change the lifted parcel path of a SP parcel, the probably won't impact MLCAPE much.  So the low-level lapse rate issue is certainly a potential bust mode.

Anymore, I find myself using 0-3km MLCAPE as my instability parameter of choice over SBCAPE, particularly with regard to tornadoes. I've found SBCAPE is best used as a discriminator as to how robust an updraft may be but not how "good" that instability is for tornadoes. That definitely applies here I think and the fact numerous models are struggling to surpass 50 3CAPE is something I find tough to ignore.

[jpeters3]

2 minutes ago, hlcater said:

Anymore, I find myself using 0-3km MLCAPE as my instability parameter of choice over SBCAPE, particularly with regard to tornadoes. I've found SBCAPE is best used as a discriminator as to how robust an updraft may be but not how "good" that instability is for tornadoes. That definitely applies here I think and the fact numerous models are struggling to surpass 50 3CAPE is something I find tough to ignore.

Where do you look at 0-3km MLCAPE?  There is a lot of recent research that supports the role of buoyancy in this layer in making/breaking tornado formation.

[hlcater]

2 minutes ago, jpeters3 said:

Where do you look at 0-3km MLCAPE?  There is a lot of recent research that supports the role of buoyancy in this layer in making/breaking tornado formation.

 

its on Sharppy skew-ts. SPC meso has a 3CAPE/LLLR crossover plot thats really helpful too

[Santa Clause]

As an amateur last two pages have been confusing a bit lol... is this trending toward less severe or more severe or stable. I see ingredients in place especially with low placement and strength and sheer but lapse rates are only average looking.

[jpeters3]

Just now, hlcater said:

 

its on Sharppy skew-ts. SPC meso has a 3CAPE/LLLR crossover plot thats really helpful too

Thanks.  I never noticed it there.

[MUWX]

1 minute ago, Wmsptwx said:

As an amateur last two pages have been confusing a bit lol... is this trending toward less severe or more severe or stable. I see ingredients in place especially with low placement and strength and sheer but lapse rates are only average looking.

High ceiling event, but there are several reasons that it could bust

[jpeters3]

3 minutes ago, Wmsptwx said:

As an amateur last two pages have been confusing a bit lol... is this trending toward less severe or more severe or stable. I see ingredients in place especially with low placement and strength and sheer but lapse rates are only average looking.

I would say the models have been trending toward a higher-end event over the last few days, in term of ingredients.  The lapse rate issue was somewhat apparent in every model solution I've seen (though it seems ever so slightly less pronounced today).  The NAM nest was a hiccup, but too early to throw in the towel.

18 UTC NAM coming in. Should we spar on this one????

[Santa Clause]

3 minutes ago, MUWX said:

High ceiling event, but there are several reasons that it could bust

Thanks!!

[Santa Clause]

3 minutes ago, jpeters3 said:

I would say the models have been trending toward a higher-end event over the last few days, in term of ingredients.  The lapse rate issue was somewhat apparent in every model solution I've seen (though it seems ever so slightly less pronounced today).  The NAM nest was a hiccup, but too early to throw in the towel.

Thanks, wrapped it up nicely. Learning from you all.

[Quincy]

Aside from model noise, the signal for a significant and potentially higher end event remains. There was a slight westward tick yesterday, but I don’t think the threat area will change all that much going forward. 

[DanLarsen34]

23 minutes ago, MUWX said:

High ceiling event, but there are several reasons that it could bust

The story of the last couple of potential high-end days. lol. We’ll see which “side” wins out. 

[Quincy]

IF the 18z NAM 3/12k suites are to be believed, the westward trend might be continuing. 

[Amped]

Just now, Quincy said:

IF the 18z NAM 3/12k suites are to be believed, the westward trend might be continuing. 

It's still not as far west as the GGEM and Euro, so it probably will.

[Quincy]

4 minutes ago, Amped said:

It's still not as far west as the GGEM and Euro, so it probably will.

At first it was the global models shifting west and the NAM lagging behind. Maybe it’s just now catching up. 

[jpeters3]

FWIW, 18 UTC NAM nest is a similar story.  Warm sector is devoid of convection closer to the cold front, and a bunch of junkvection further east....

 

Interested to see what CAMs do tomorrow.