Severe Weather Threat - May 6, 2024

[jiharris0220]

The convective inhibition being talked about here isn't a capping inversion. It's the nightly nocturnal low-level inversion that develops on the Plains from boundary layer decoupling. It happens after sunset; so, the amount of sunshine tomorrow has nothing to do with it. We're not looking for it to be broken or eroded because it won't be (although it may not build in as fast, the stronger the low-level winds are). We are looking for supercellular updrafts to get rooted in the surface-based inflow layer prior to it getting established.

I know, but I’m specifically talking about the CIN in this case, as high low level lapse rates are needed to over come that.

And minimum cloud cover will most definitely help with this.

 

[MichelleH]

OK, the members have spoken. This is now the thread for ONLY Monday, May 6th, and there is a new thread for the rest of the week.

 

[Fred Gossage]

I know, but I’m specifically talking about the CIN in this case, as high low level lapse rates are needed to over come that.

And minimum cloud cover will most definitely help with this.

And I'm explaining to you that the CIN being talked about comes from a completely different mechanism and isn't modulated or overcome by the factors you're looking at. The amount of cloud cover during the daytime has zero influence on whether it develops because it doesn't develop until after dark as the surface cools after sunset. And that means, if anything, having enhanced cloud cover during the evening would actually slow its development because that would lead to less radiational cooling of the surface. This nocturnal CIN is controlled by the after dark decoupling of the boundary layer, and how fast that happens is controlled by (and only by) things that offset nocturnal radiational cooling of the earth's surface: stronger low-level winds to keep the lower atmosphere mixed instead of it stratifying into layers from the surface cooling and air above it being warmer, higher moisture content in the low-levels because moist air heats and cools less efficiently than drier air, more cloud cover to act as an insulating blanket and keep heat from radiating out into space.

 

[jiharris0220]

I think you’re misunderstanding me, I’m not disagreeing with you.

I’m saying I was specifically talking about the CIN, nothing else.

Is CIN not the amount of energy required to overcome negative buoyancy the environment superimposes on an air parcel?

Would that not involve lapse rates?

 

[andyhb]

I think you’re misunderstanding me, I’m not disagreeing with you.

I’m saying I was specifically talking about the CIN, nothing else.

Is CIN not the amount of energy required to overcome negative buoyancy the environment superimposes on an air parcel?

Would that not involve lapse rates?

I think he's pointing out that in the original tweet that you were referencing, the "inhibition" being shown is a result of boundary layer decoupling and not the elevated mixed layer (cap). Lapse rates are less important if the surface layer is stable (well you can still get elevated severe storms, but less tornado threat).

 

[KevinH]

Oh I know haha I’m just being silly.

Fair enough lol

 

[jiharris0220]

I think he's pointing out that in the original tweet that you were referencing, the "inhibition" being shown is a result of boundary layer decoupling and not the elevated mixed layer (cap). Lapse rates are less important if the surface layer is stable (well you can still get elevated severe storms, but less tornado threat).

Ah, thanks a lot, I was getting confused there on what exactly was the thing he was referring to.

Although I don’t think I mentioned anything about EML/cap?

 

[tennessee storm chaser]

Anyone picking up on a cips analog 2003 yet? May

 

[Fred Gossage]

I think you’re misunderstanding me, I’m not disagreeing with you.

I’m saying I was specifically talking about the CIN, nothing else.

Is CIN not the amount of energy required to overcome negative buoyancy the environment superimposes on an air parcel?

Would that not involve lapse rates?

I'm not misunderstanding you. CIN can develop from different driving mechanisms in the atmosphere, can be located in different layers of the atmosphere depending on said mechanism, and is removed or overcome (or not) in different ways depending on which mechanism has caused it to develop. This would be CIN developing from a low-level inversion that doesn't develop until after dark. That means 1.) daytime cloud cover mentioned before has nothing to do with it, and 2.) the mere presence of the inversion that creates the CIN even being there will change the low-level lapse rate environment from what it is in the afternoon... and if storms get rooted in the surface-based inflow layer prior to that inversion/CIN developing after dark, supercells will be able to be surface-based and be capable of producing large tornadoes, regardless of that inversion/CIN developing and how the low-level lapse rates are modulated because of it. CIN does not always equal mid-level capping. For example, you can actually have strong CIN and a completely uncapped atmosphere if the boundary layer is dry enough.

 

[jiharris0220]

I'm not misunderstanding you. CIN can develop from different driving mechanisms in the atmosphere, can be located in different layers of the atmosphere depending on said mechanism, and is removed or overcome (or not) in different ways depending on which mechanism has caused it to develop. This would be CIN developing from a low-level inversion that doesn't develop until after dark. That means 1.) daytime cloud cover mentioned before has nothing to do with it, and 2.) the mere presence of the inversion that creates the CIN even being there will change the low-level lapse rate environment from what it is in the afternoon... and if storms get rooted in the surface-based inflow layer prior to that inversion/CIN developing after dark, supercells will be able to be surface-based and be capable of producing large tornadoes, regardless of that inversion/CIN developing and how the low-level lapse rates are modulated because of it. CIN does not always equal mid-level capping. For example, you can actually have strong CIN and a completely uncapped atmosphere if the boundary layer is dry enough.

I get what you’re saying, I’m just a bit confused because I was specifically talking about CIN, and nothing about cap/EML.

 

[Fred Gossage]

I get what you’re saying, I’m just a bit confused because I was specifically talking about CIN, and nothing about cap/EML.

Convective inhibition is an after product of there being an inversion in a layer of the atmosphere. The kind of CIN you were talking about, that is overcome by daytime heating and is tied to low-level lapse rates under the inversion, is from mid-level capping and the EML. It is not the type of CIN that's being modeled for Monday evening and night, and Monday night's type of CIN is not controlled or overcome by those factors. The type of CIN being modeled for Monday night is caused by a near-surface nocturnally driven inversion where the temperature increases with height from the ground to the bottom of that inversion layer. That means any steep lapse rates, even in the "lower-levels" are located fully above the inversion and not below it.

 

[jiharris0220]

Convective inhibition is an after product of there being an inversion in a layer of the atmosphere. The kind of CIN you were talking about, that is overcome by daytime heating and is tied to low-level lapse rates under the inversion, is from mid-level capping and the EML. It is not the type of CIN that's being modeled for Monday evening and night, and Monday night's type of CIN is not controlled or overcome by those factors. The type of CIN being modeled for Monday night is caused by a near-surface nocturnally driven inversion where the temperature increases with height from the ground to the bottom of that inversion layer. That means any steep lapse rates, even in the "lower-levels" are located fully above the inversion and not at the ground.

But is an EML and cap not a type of inversion?

Edit (if this is a stupid question I apologize before hand)

 

[Fred Gossage]

But is an EML and cap not a type of inversion?

Edit (if this is a stupid question I apologize before hand)

Yes, in a higher layer of the atmosphere than the inversion that is driving Monday night's modeled CIN.

Here is the difference:

 

[jiharris0220]

Yes, in a higher layer of the atmosphere than the inversion that is driving Monday night's modeled CIN.

Here is the difference:
View attachment 26316

Thank you for the chart, explains your point to me significantly.

But for Oklahoma specifically there does seem to be a weak inversion (the first type in the chart) around 850-700mb.

 

[Fred Gossage]

Note that in the case of the nocturnal inversion in my diagram above, it won't prevent storms from forming because there is still a moist atmosphere for a bit of depth above the inversion layer. Any storm not rooted below that inversion before it develops would be elevated instead of surface-based, but they would still be able to form. So, that type of inversion is not a "cap". In the case of the EML-driven mid-level inversion on the left, storms wouldn't be able to form. From the base of the inversion and upward, the atmosphere is dry. You might get shallow showers or a thunderstorm to form in the low-levels under that inversion, but they wouldn't push through it without the inversion being eroded or a forcing mechanism overcoming it. That type of inversion is a "cap".

 

[Tempestas Tonitrua]

Thank you for the chart, explains your point to me significantly.

But for Oklahoma specifically there does seem to be a weak inversion around 850-700mb.
View attachment 26317

I’ve actually noticed in a lot of plains events, just because its proximity to the EML source region, a cap or warm nose can slowly build back in as the day goes on.

Now, not sure that that’s what’s happening in that sounding but something I’ve noticed nonetheless

 

[Fred Gossage]

Thank you for the chart, explains your point to me significantly.

But for Oklahoma specifically there does seem to be a weak inversion around 850-700mb.
View attachment 26317

That would be a cap from the EML. Note there's not an inversion based at the surface. That doesn't have the nocturnal-driven CIN. Note that the CIN values in the chart are little to none. In this scenario, storms would either be capped off because of that mid-level inversion or forcing would push the updrafts through it.

 

[Tempestas Tonitrua]

That would be a cap from the EML. Note there's not an inversion based at the surface. That doesn't have the nocturnal-driven CIN. Note that the CIN values in the chart are little to none. In this scenario, storms would either be capped off because of that mid-level inversion or forcing would push the updrafts through it.

Fred, I know you’re a busy man, but I’d watch you lecture or comment on the “x’s and o’s” of meteorology in some kind of YouTube video series any day.

 

[Fred Gossage]

Somewhat of a side note but strongly related... This illustrates the "danger" of blindly using CIN as a map-based proxy for capping without looking at sounding profiles, as MANY people out there do. You can have a decent cap like shown in that forecast sounding, but little to no CIN at all because of where the parcel lapse rate is drawn on the skew-T. Conversely, you can also have strong CIN in the low-levels of the atmosphere from a dry boundary layer, but actually have a completely uncapped profile with no temperature inversion anywhere in sight.

 

[jiharris0220]

So the type of CIN you’re talking about would be something like this.

Where a warm nose near the surface pushes the LFC upwards which keeps storms from being surfaced base, if they don’t develop before it sets in.