"Cold core" lows

[Andy Wehrle]

Mickey said "10-9-01 was not a cold-core setup while this upcoming one is". What exactly is "cold core"? Aren't all midlatitude/extratropical cyclones that provide the synoptic setup for most severe weather outbreaks "cold core" (versus "warm core" tropical cyclones)?

 

[Mickey Ptak]

From what I understand a Cold Core is a Low that is stacked on top of itself at the various levels.

Correct me if I am wrong...

Edit:
I correct myself I guess here is what I have found on "Cold Core Low"

COLD LOW
A low pressure system that has its coldest temperatures at or near the center of circulation, and is thermally barotropic with respect to a horizontal plane. Also known as a cold core low. A cut off low is an example, where an isolated pool of colder air is located south of the main westerlies.

From what I have observed, from this year alone, is that the cold core setups we have had in 2005 where always stacked on top of themselves at the verious levels. So that is where I have come up with the "cold core low".

Mick

 

[Robert Dewey]

Originally posted by Mickey Ptak
From what I have observed, from this year alone, is that the cold core setups we have had in 2005 where always stacked on top of themselves at the verious levels. So that is were I have come up with the \"cold core low\".

Mick

I don't know if being "cold core" has anything to do with the breaking of events. I think the biggest breaker was the fact that the shortwaves became cutoff and vertically stacked - at which point most systems begin the weakening process / shear out. That would mean the wind field would become less organized, vorticity advection begins to cease as the system slows, and any convergence would begin to subside as forward momentum of cold fronts / drylines slows down.

An example of a true "cold core" low would be a winter storm that develops north of the baroclinic zone...

EDIT: After reading your (Mick's) other post in the "Upcoming active week" thread, I can see that's the point you were trying to make - vertically stacked and closed off systems aren't really good producers... Although the GFS shows this system as being only weakly closed - but it's strongly positively tilted...

 

[Mickey Ptak]

Originally posted by rdewey+--><div class='quotetop'>QUOTE(rdewey)</div>

<!--QuoteBegin-Mickey Ptak

From what I have observed, from this year alone, is that the cold core setups we have had in 2005 where always stacked on top of themselves at the verious levels. So that is were I have come up with the \"cold core low\".

Mick

I don't know if being "cold core" has anything to do with the breaking of events. I think the biggest breaker was the fact that the shortwaves became cutoff and vertically stacked - at which point most systems begin the weakening process / shear out. That would mean the wind field would become less organized, vorticity advection begins to cease as the system slows, and any convergence would begin to subside as forward momentum of cold fronts / drylines slows down.

An example of a true "cold core" low would be a winter storm that develops north of the baroclinic zone...

EDIT: After reading your (Mick's) other post in the "Upcoming active week" thread, I can see that's the point you were trying to make - vertically stacked and closed off systems aren't really good producers... Although the GFS shows this system as being only weakly closed - but it's strongly positively tilted...[/b]

Well that makes sense really... So what I am thinking of (and trying to get across) is indeed not a "Cold Core Low" but rather a "vertically stacked" Low? Let me ask another question, are most cut off lows vertically stacked?

Mick

 

[mikegeukes]

Jon Davies
http://members.cox.net/jondavies1/tornado_...oldcorelow_tors
http://ams.confex.com/ams/pdfpapers/81563.pdf

Haby Hints
http://www.theweatherprediction.com/basic/.../pressuretypes/
http://www.theweatherprediction.com/blocking/

Mike
http://mgweather.com

 

[Jayson Prentice]

Originally posted by Mickey Ptak


Well that makes sense really... So what I am thinking of (and trying to get across) is indeed not a \"Cold Core Low\" but rather a \"vertically stacked\" Low? Let me ask another question, are most cut off lows vertically stacked?

Mick

From what I understand about cut off lows is that they are for the most part vertically stacked. This is because for the cut off low to be a cut off, it has to be lost from the main upper level flow. So in which case as the low becomes closed it stacks itself in order to maintain a low pressure system.

And I believe that this is the point where it will either stack itself up and maintain itself for a while longer or it begins to fall apart.

Am I right here?

 

[Michael P. Morris]

Technically, a cold core low means that the circulation is cyclonic at all levels. This is a consequence of the thermal wind relationship caused by cold air being at the center of the system all the way up. Troughs in the midlatitudes are cold core nearly exclusively. Contrast this with a hurricane, which has a pool of warm air aloft generated by latent heating. The thermal wind changes direction at some altitude aloft due to the change in the temperature gradient and you get an anticyclonic circulation at high levels above the hurricane.

When a low becomes vertically stacked, there is no advection aloft to force rising motion and the system tends to weaken. This is a good reason why vertically stacked systems are not good producers. The lack of advection means you don't get the 500 mb height falls and vorticity advection out ahead of the trough (as one would get with a nice open wave system) that would help force severe convection.