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Pattern The Great December Dump

Webberweather53 said:
There's definitely signs of increasing wave - 1 forcing from the troposphere in the extended as our big Scandinavian high tries to make a comeback along w/ the deep Bering Sea/AK vortex. The good thing is in a pattern like this the warm ups are going to be transient/short-lived in the grand scheme of things. Our next legit round of -NAO after this upcoming week is probably coming sometime in early January based on the SCAND progression.
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;) ... :cool: ...
 
We're going to need a lot more where this came from to have legitimate hope for a winter storm even up here in NC.

At least 3-4 EPS members showing snow around the solstice is better than 0...

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Going to need some cad to save us on the temps. Euro had some signs of it.
 
Euro suppressed at this stage is a good sign, but lets not forget the basics for a south of 40N major event.

Suppressed signal 3-7 days out from Euro - Yes
Cross polar flow - No
50/50 displaced slightly south - Maybe Yes, but transient and weak, so No
Stout PNA following Continental divide or just east (Chicago does not count) - No
Some flavor of northern stream interaction (not a requirement) - No, but it helps
Nearby cold air source, preferably Arctic in origin - No
In absence of cold source, H5 cutoff, sub 540dm, with a late close (LA) and aggressive right hook - No
 
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WeatherNC said:
Euro suppressed at this stage is a good sign, but lets not forget the basics for a south of 40N major event.

Suppressed signal 3-7 days out from Euro - Yes
Cross polar flow - No
50/50 displaced slightly south - Maybe Yes, but transient and weak, so No
Stout PNA following Continental divide or just east (Chicago does not count) - No
Some flavor of northern stream interaction (not a requirement) - No
Nearby cold air source, preferably Arctic in origin - No
In absence of cold source, H5 cutoff, sub 540dm, with a late close (LA) and aggressive right hook - No
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The aforementioned Feb 2004 storm that bears some similarities at 500mb to next week's upper low is actually a great example that meets virtually none of the above requirements with exception to the 50/50 low.

If there's going to be any room for improvement for next week's setup, I think the 50/50 low is the most likely to be where it occurs (if at all)

In Feb 2004's case:
-There was no cross-polar flow
-No true arctic air & basically no surface cold high (1034 over Northern Quebec is a joke)
-Basically zero northern stream interaction
-The H5 cut-off upper low over the southern US wasn't even below 552dm, much less 540dm
-There was a -PNA to boot w/ a trough on the west coast & the ridge axis ironically was centered over Chicago/Lake Michigan.

As nice as some of your basic rules are for southern storms, there are many instances like Feb 2004 that break nearly all of them and still produce a massive storm.



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Webberweather53 said:
The aforementioned Feb 2004 storm that bears some similarities at 500mb to next week's upper low is actually a great example that meets virtually none of the above requirements with exception to the 50/50 low.

If there's going to be any room for improvement for next week's setup, I think the 50/50 low is the most likely to be where it occurs (if at all)

In Feb 2004's case:
-There was no cross-polar flow
-No true arctic air & basically no surface cold high (1034 over Northern Quebec is a joke)
-Basically zero northern stream interaction
-The H5 cut-off upper low over the southern US wasn't even below 552dm, much less 540dm
-There was a -PNA to boot w/ a trough on the west coast & the ridge axis ironically was centered over Chicago/Lake Michigan.

As nice as some of your basic rules are for southern storms, there are many instances like Feb 2004 that break nearly all of them and still produce a massive storm.



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The base state has warmed since then making it harder to cool the boundary layer.


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BHS1975 said:
The base state has warmed since then making it harder to cool the boundary layer.


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Well considering that storm happened almost at the beginning of March when our climatology is several degrees warmer than it is in late December, this point is pretty mute.
 
Webberweather53 said:
The aforementioned Feb 2004 storm that bears some similarities at 500mb to next week's upper low is actually a great example that meets virtually none of the above requirements with exception to the 50/50 low.

If there's going to be any room for improvement for next week's setup, I think the 50/50 low is the most likely to be where it occurs (if at all)

In Feb 2004's case:
-There was no cross-polar flow
-No true arctic air & basically no surface cold high (1034 over Northern Quebec is a joke)
-Basically zero northern stream interaction
-The H5 cut-off upper low over the southern US wasn't even below 552dm, much less 540dm
-There was a -PNA to boot w/ a trough on the west coast & the ridge axis ironically was centered over Chicago/Lake Michigan.

As nice as some of your basic rules are for southern storms, there are many instances like Feb 2004 that break nearly all of them and still produce a massive storm.



View attachment 28168
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The airmass ahead of that storm certainly wasn’t overwhelming cold either. Highs around 50 the day before the storm in CLT and two days after it was pushing 60.
 
BHS1975 said:
The base state has warmed since then making it harder to cool the boundary layer.


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That has nothing to do with bringing up relatively recent analogs for one, and for second this is the Dec discussion, not GW related. Also as Webb mentioned, this point is not even worth bringing up because it's not even the same month. It's December which is cooler than early March anyway. Also there hasn't been that much warming and patterns cancel out that very meager degree that could or could not even have an impact.
 
Timing wise, I'd really like to see our shortwave speed up a bit or for the 50/50 low slow down and dig south some more. Take it fwiw, the GEFS/GFS have been trending towards a slower/southward displaced 50/50 low around day 5-6, however I'm not sure if it's gonna be enough. We really need to see a lot more of this where it came from the next few days to have much hope for something substantial in the climatologically more favored portions of the upper south.


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Unsure about the mute point, but to keep it honest, 2004 had ridging in to the Canadian Rockies, a function of a 985 about to impact the Cascades. 2019 also needs to subtract 20MB from the Bay of Fundy and add a neg NAO.
 

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WeatherNC said:
Unsure about the mute point, but to keep it honest, 2004 had ridging in to the Canadian Rockies, a function of a 985 about to impact the Cascades. 2019 also needs to subtract 20MB from the Bay of Fundy and add the neg NAO.
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There was no anomalous ridging over the Canadian Rockies in Feb 2004. Instead, we had a Rex Block centered over the Hudson Bay w/ a shortwave ridge axis extending down into the central US. Keep in mind there's usually a ridge over the Rockies in the means.

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