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Pattern The Great December Dump

SD said:
I think its happening man. I could fall flat on my face but is really difficult to not go all in on January

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My excitement is about as high as it could be given what I'm seeing in January this far in advance. There's still some ways we could easily screw this up & for the fact that the 2+ weeks out but the general signs seem to be there as well as what we've seen so far this December.

We've had a parade of southern stream systems the last several weeks (w/ this week's being another example) & a few legitimate bouts of negative NAO this month & in November despite the strong +IOD that usually favors a torch in early winter & raging +NAO. Coming out moderately above normal with even a few glimmers of hope for wintry weather & some -NAO sprinkled in is a win by my standards & a telling sign considering the hand we've been dealt this month.

It is very hard for me to not be excited about what may potentially be around the corner when we're about to add some high-latitude North Pacific blocking into the mix coupled with better subseasonal tropical forcing in early January.
 
Webberweather53 said:
My excitement is about as high as it could be given what I'm seeing in January this far in advance. There's still some ways we could easily screw this up & for the fact that the 2+ weeks out but the general signs seem to be there as well as what we've seen so far this December.

We've had a parade of southern stream systems the last several weeks (w/ this week's being another example) & a few legitimate bouts of negative NAO this month & in November despite the strong +IOD that usually favors a torch in early winter. Coming out moderately above normal with even a few glimmers of hope for wintry weather is a win by my standards considering the hand we've been dealt this month. It is very hard to not be excited about what may potentially be around the corner when you add some high-latitude North Pacific blocking into the mix coupled with better subseasonal tropical forcing in early January.
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We have been stuck in this wet pattern for a month now, where it's rained here at least once every week. It doesn't look like that's going to let up any time soon, either. Until we start to see a stretch of dry weather, there's no reason not to be optimistic with the way things have been here since November. We just need the cold to go with it, and that should be easier to get in January. It's not like we have had any sustained periods of above normal temps since November, too. We are definitely headed in the right direction versus going the wrong way.
 
Lots of rain headed here with imbedded thunderstorms, some of which could be severe in isolated areas..
 
The EPS looks much worse than the GEFS in the longer term. However, the EPS hasn't exactly had a good track record in sniffing out -EPO events, even inside 7-10 days. In reality, these wave breaks that are critical to generating high amplitude North Atlantic & North Pacific blocks/ -NAO & -EPO are usually dampened and less meridionally extensive at large leads due to increasing spread w/ range & biases in the model(s) & highly dependent on individual synoptic-scale events that grow upscale rather quickly & simply can't be resolved more than a week or so out. The basic ingredients are there for a much better pattern in early January imo and that's what really matters at this juncture.
 
Webberweather53 said:
The EPS looks much worse than the GEFS in the longer term. However, the EPS hasn't exactly had a good track record in sniffing out -EPO events, even inside 7-10 days. In reality, these wave breaks that are critical to generating high amplitude North Atlantic & North Pacific blocks/ -NAO & -EPO are usually dampened and less meridionally extensive at large leads due to increasing spread w/ range & biases in the model(s) & highly dependent on individual synoptic-scale events that grow upscale rather quickly & simply can't be resolved more than a week or so out. The basic ingredients are there for a much better pattern in early January imo and that's what really matters at this juncture.
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Related to this Webb post:

“Shifts in the northern Pacific are worth watching in the final days of December and into early January, as models start to build a ridge toward Alaska. The GFS EN is fastest in evolving the –EPO/+TNH among this morning’s models, an important development as it could allow for the connection to colder source regions. That said, the Euro EN has slowed this evolution from earlier model runs, and the GFS EN has carried a recent Alaska ridge bias in the 11-15 Day period. Based on late month trends in the north Pacific, there is potential for a colder pattern to evolve. Any colder periods resulting are likely beyond the current 11-15 Day window, however.”
from Maxar

Reading between lines, the GEFS may be too fast based on bias but EPS may be too slow based on its bias. So, best guess may be timing between the two. Regardless, we’re likely looking at early January before major cold impacts to the SE could possibly occur from this. Cold impacts up in the upper Midwest/Plains/Rockies would likely come a good number of days sooner.
 
Jimmy Hypocracy said:
Glad we’re back up and running. Papa’s got
A brand new bag!View attachment 28386
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I think what is frustrating is watching run after run consistency when it comes to 10°+ AN temps around Xmas while bouncing around all over the place with the marginal snow threat next week.


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ATLwxfan said:
I think what is frustrating is watching run after run consistency when it comes to 10°+ AN temps around Xmas while bouncing around all over the place with the marginal snow threat next week.


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What's frustrating is we get a locked in warm pattern for the next 2+ weeks easy peezy, but a locked in cold pattern never happens. Better now than mid January I guess.
 
GaWx said:
Related to this Webb post:

“Shifts in the northern Pacific are worth watching in the final days of December and into early January, as models start to build a ridge toward Alaska. The GFS EN is fastest in evolving the –EPO/+TNH among this morning’s models, an important development as it could allow for the connection to colder source regions. That said, the Euro EN has slowed this evolution from earlier model runs, and the GFS EN has carried a recent Alaska ridge bias in the 11-15 Day period. Based on late month trends in the north Pacific, there is potential for a colder pattern to evolve. Any colder periods resulting are likely beyond the current 11-15 Day window, however.”
from Maxar

Reading between lines, the GEFS may be too fast based on bias but EPS may be too slow. So, best guess may be timing between the two. Regardless, we’re likely looking at early January before major cold impacts to the SE could possibly occur from this. Cold impacts up in the upper Midwest/Plains/Rockies would likely come a good number of days sooner.
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Yeah I can agree with the above post from Maxar to some extent. The GEFS is almost assuredly too fast w/ CCKWs & the MJO in the Pacific-W Hem which causes the pattern to evolve more quickly than on the EPS aside from the GEFS having a LR -EPO bias but the EPS rarely if ever sees a -EPO until its virtually too late & I definitely think it's underselling the amplitude & meridional extent of the AK ridge in the longer-term. We'll probably have enhanced warm risks & a stronger SE US ridge right before the pattern becomes well established.

I'd wager that the pattern flips for us around January 5-10 ish.

This recurring rossby wave train (RRWT) tool developed by Josh Herman (http://www.consonantchaos.com/f-all.html) seems to generally concur w/ this idea timing-wise. The overall progression also appears to line up w/ what I'm seeing in the models and would expect from this bout of "blue-shifted" subseasonal forcing & how -EPO/+TNHs tend to evolve w/ cold usually being dumped into the western US and Rockies first before entering the E US.

Each image below in this animation is a RRWT forecast valid for days 6-10, 11-15, 16-20, & 21-25 respectively.

The hammer really comes down in the 21-25 (valid Jan 6-10)
Webp.net-gifmaker (7).gif
 
18z gfs is a good illustration of what a lot of the chatter for January is about. Is it too fast? Probably. Are the pieces what is being talked about? Absolutely. I said it earlier and I'll say it again I'm chips to the middle of the table all in for January, if it fails I apologize in advance. Its been a while since we had an active STJ coupled with the actual potential to see an epo ridge/pna ridge.

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Christmas wedge
O Christmas wedge
How excited am I to see the

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ad5c302579ced6c8dfb956bbe80ed3f8.jpg
 
SD said:
18z gfs is a good illustration of what a lot of the chatter for January is about. Is it too fast? Probably. Are the pieces what is being talked about? Absolutely. I said it earlier and I'll say it again I'm chips to the middle of the table all in for January, if it fails I apologize in advance. Its been a while since we had an active STJ coupled with the actual potential to see an epo ridge/pna ridge.

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What’s too fast about it? Late December and early January is what we’re talking about isn’t it?
 
Nick_boynton_ said:
What’s too fast about it? Late December and early January is what we’re talking about isn’t it?
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Gfs is generally too fast with its wave/mjo progression so it's too fast with its resultant pattern changes. In all reality its probably 5-7 maybe 10 days quick on the 18z

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Nick_boynton_ said:
What’s too fast about it? Late December and early January is what we’re talking about isn’t it?
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GFS is the more progressive of the global models. It’s end game is usually modeled too far in advance. “Second mouse gets the cheese.” kind of deal. First mouse had the right idea, but was way too early. So it died
 
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