• Hello, please take a minute to check out our awesome content, contributed by the wonderful members of our community. We hope you'll add your own thoughts and opinions by making a free account!

Pattern December to Remember

Rain Cold said:
I don't get the infatuation with the MJO. I mean, it's not unimportant, but it isn't operating in a vacuum, and there are certainly other factors influencing the atmosphere. If it was as easy as some Twitter jabronis would lead you to believe, we could ignore everything else and focus on nothing ever but the MJO.

It's funny because when the MJO is in the warm phases and it's actually warm, it gets all the credit. But when it's in the cool phases and it's warm, oh well it's because it's overwhelmed by something else.

The popular modern day approach is to distill a complex and chaotic system down to an index. Twitter people learn a new 3 letter acronym and go to town. At least the SAI has been largely put to bed.
Click to expand...

The MJO has been around since the 1970s (1974 to be exact), it's nothing new (maybe for certain people it is), the SAI barely survived a decade of scrutiny.
 
StormWatch said:
Some thoughts about the large scale pattern that could lead to a colder pattern across the eastern US. I have done some observations and I'd say a colder pattern may return in about 2 - 2 and a half weeks. Weather systems will be cutting, tracking into eastern Canada and eventually out over the very far northern portion of the Atlantic - these storm systems would eventually lead to Greenland blocking because the systems would enhance sinking air (blocking) north of the storm systems. A -NAO maybe seen in the foreseeable future. A stationary high could get locked into place north of Europe over the Arctic Ocean due to blocking over Greenland and storm systems tracking across central/northern Russia keeping the high locked into place. This stationary high would be good, because it would help elongating the PV on a northwest to southeast axis. I think the stubborn blocking over the EPO region is what's going to be the biggest issue. However, the storm systems that track from Russia to the Bearing Sea towards AK is what could help force the North Pacific blocking to go poleward, being replaced with a trough. We'll see what plays out upstream over the Pacific within the next week or so. If everything comes together from what I have observed, we may very well see better setups at 500mb in the LR, concerning colder air. Any questions, feel free to ask!
Click to expand...

I think you have the right general idea, but I honestly don't believe it'll occur quite as quickly as you're describing. At a minimum, given how this is being forced, it looks like it'll take us no less than 3 weeks to shake off this bad pattern, we'll probably still be right in the thick of it in about 2 weeks time (doesn't mean we can't get a transient cold shot here or there though, and I honestly expect at least one between now and then).

Big reason for that is it takes weeks for the extratropical circulation pattern to change and readjust after getting a large, slow moving MJO event like this one moves across the Maritime Continent and into the Western Pacific, as the planetary Rossby Waves forced by the slower-moving moist convective anomalies become exhibit higher growth rates/become amplified and are harder to break down, this is even more of an issue when you have La Nina and these circulation anomalies are already being enhanced in the lower frequency (90-120 day) means. Normally, the possibility of a -NAO in late December would be a decent bet, but that connection isn't quite as strong during La Nina (although it's more likely when an MJO event is slow moving such as this one, but you're still normally talking at least a week or two after we enter phase 7 for extratropical circulation anomalies to consistently resemble said -NAO, which at least puts us closer to the last week of Dec or so). It's also very possible we never even reach the coveted phase 8/W hem (not uncommon during La Nina when SSTs are too cold to support convection closer to the dateline), which would support more consistent cold in the eastern US.

Just my 2 cents tho.
 
Webberweather53 said:
I think you have the right general idea, but I honestly don't believe it'll occur quite as quickly as you're describing. At a minimum, given how this is being forced, it looks like it'll take us no less than 3 weeks to shake off this bad pattern, we'll probably still be right in the thick of it in about 2 weeks time (doesn't mean we can't get a transient cold shot here or there though, and I honestly expect at least one between now and then).

Big reason for that is it takes weeks for the extratropical circulation pattern to change and readjust after getting a large, slow moving MJO event like this one moves across the Maritime Continent and into the Western Pacific, as the planetary Rossby Waves forced by the slower-moving moist convective anomalies become exhibit higher growth rates/become amplified and are harder to break down, this is even more of an issue when you have La Nina and these circulation anomalies are already being enhanced in the lower frequency (90-120 day) means. Normally, the possibility of a -NAO in late December would be a decent bet, but that connection isn't quite as strong during La Nina (although it's more likely when an MJO event is slow moving such as this one, but you're still normally talking at least a week or two after we enter phase 7 for extratropical circulation anomalies to consistently resemble said -NAO, which at least puts us closer to the last week of Dec or so). It's also very possible we never even reach the coveted phase 8/W hem (not uncommon during La Nina when SSTs are too cold to support convection closer to the dateline), which would support more consistent cold in the eastern US.

Just my 2 cents tho.
Click to expand...


Here's a nice paper published a few years ago that reinforces my overall sentiment here w/ a slower-moving MJO favoring a more prolonged warm-up in Dec that could last thru the end of the month.

https://journals.ametsoc.org/view/journals/clim/32/21/jcli-d-19-0013.1.xml#fig12

A few key takeaways:

MJO moves ~30% slower on avg during La Nina winters (like this yr) due to how ENSO modulates suppressed convection in
the W Pac (weaker zonal moisture advection/less suppressed convection in La Nina >> slower MJO). Congestus preconditions the environment for deeper vertical heating associated w/ the MJO. Weaker Kelvin Wave activity over the WP during La Nina suppresses pre-moistening, making the environment less suitable for convection east (ahead of) the MJO's convective center.

Sronger Eq Rossby Wave coupling in La Nina contributes to a more profound beta effect >> more retrogression/slower eastward-moving MJO.

Stronger/slower MJO events in La Nina increase the growth rates of anomalous large-scale planetary waves in the subtropics and mid-latitudes (which tend to retrograde westward) and are coupled + evolve together w/ the MJO, helping to slow the MJO's phase speed in La Nina.

Stronger convection over the Warm Pool during La Nina slows the progression of Kelvin Waves (which constitute a large fraction of the MJO) by further offsetting adiabatic cooling that occurs in the ascending (leading) part fo the wave. Chang (1977)
 
NickyBGuarantee said:
View attachment 96689??
Click to expand...

Looks like there’s potential for a transient cold shot in the midst of a really warm pattern overall (which is something I mentioned in an earlier post). The operational isn’t supported by its own ensemble (or the gefs), so I expect that deep trough to disappear on the next run. Not totally out of the realm of possibility tho we see a decent looking trough for a few days remind SE US folks it’s still winter

1638531556401.png
 
Last edited:
I could certainly see a cold shot or two in the midst of this warm pattern. The typhoon curving out to sea in the west pac may shorten the wavelengths just enough temporarily to allow a trough in the east for a day or two. Unfortunately, it’s not the answer to consistent cold in the long run.
 
Webberweather53 said:
I could certainly see a cold shot or two in the midst of this warm pattern. The typhoon curving out to sea in the west pac may shorten the wavelengths just enough temporarily to allow a trough in the east for a day or two. Unfortunately, it’s not the answer to consistent cold in the long run.
Click to expand...
I’ve been trying to say this most models other than the GFS try to bring bouts of relief in a dumpster fire pattern and it’s not going to be a full on torch constantly as GFS has been trying to point at although recent run is starting to follow suit
 
NickyBGuarantee said:
I’ve been trying to say this most models other than the GFS try to bring bouts of relief in a dumpster fire pattern and it’s not going to be a full on torch constantly as GFS has been trying to point at although recent run is starting to follow suit
Click to expand...
0z euro was a monster east coast trough around Dec 13th. Will be interesting to see today’s 12z run.
 
SD said:
Euro control trying to pull out an island of cold in a sea of warm and blow up a coastal snow brings a tear to my eye. Close to the Jan 02 look but not quite there, 02 was a little more west with its features and the ridging was more in NW can
Click to expand...
You can’t just not show us this
 
Myfrotho704_ said:
The cooler 12z euro (still warm) only has 1-2 CAD days to several 60/70 degree daysView attachment 96666

the GFS has something similar as well with some dec 7-8th CADView attachment 96667
Doesn’t seem very “even” to me, the CAD is mad weak per current models. Everyone is getting the torch bud ain’t no escaping the dec weenie roast
Click to expand...
These are forecasts that are from one run and span over 2 weeks. You will see that change a 1000x. Also CAD typically starts getting depicted closer in the medium and short range so I doubt we will see it on models beyond a day 5 right now. But you start pumping a SE ridge and get cutting storms that will make it to the 50/50 region and you will see CAD showing up a lot more which is typical for this type of pattern. May not be a week long CAD event (although that does happen quite a bit) but at least a couple of days of cold and dreary weather in the midst of 60's and 70's is likely. Rarely do we get the SER, especially the one depicted on the GFS, and don't CAD quite a bit as well.
 
You must log in or register to reply here.
Back
Top