December 2012 Pattern Analysis

[bluewave]

The NAEFS are hinting that it may take until after the New Year sometime to get the ball rolling

toward a colder pattern if some of the analogs that we have been discussing toward closer

to normal or colder work out.

The Euro is also backing off the cold it was forecasting for next weekend.

old euro forecast

new euro forecast

[PB GFI]

The NAEFS are hinting that it may take until after the New Year sometime to get the ball rolling

toward a colder pattern if some of the analogs that we have been discussing toward closer

to normal or colder work out.

The Euro is also backing off the cold it was forecasting for next weekend.

old euro forecast

new euro forecast

The NAEFS were spot on last year predicting temps , when everyone was touting the Strat Warm , That is not a good sign AT ALL .

[easternsnowman]

Remember thr trends since march 2010....very little below normal months and most above. I still believe 2 or 3 above normal is the new normal and that is what we can expect.

[TWCCraig]

12 OP GFS completely abolishes any decent snowfall. Even takes NAO significantly positive. Not liking that, hopefully it changes.

[MJO812]

I haven't seen a map like this in a few years

[earthlight]

12 OP GFS completely abolishes any decent snowfall. Even takes NAO significantly positive. Not liking that, hopefully it changes.

These operational models change every run. Why do we continue to worry about their specific solutions? Ensembles are so incredibly useful in patterns like this.

[jrodd321]

These operational models change every run. Why do we continue to worry about their specific solutions? Ensembles are so incredibly useful in patterns like this.

How anyone can take one model run completely serious right now in this pattern is beyond me. They are literally changing every run, it's amusing. Like John said, go with the ensembles during this pattern change that is currently evolving in the upper atmosphere.

[Chris L]

I haven't seen a map like this in a few years

ECMWF looks a bit like February 2010; January 1996 with the core trough centered in the Mid-Atlantic...

[nzucker]

18z GFS also offered some hope with the -NAO bringing in moderate cold and snow chances before XMAS and then a large blocking high developing over the GoA, leading to very cold weather in the long-range, especially over the nation's midsection. The signal for a change in the Pacific has definitely been growing stronger with the last few GFS runs and the 12z ECM also showing heights rises out west at Day 10..

[TWCCraig]

How anyone can take one model run completely serious right now in this pattern is beyond me. They are literally changing every run, it's amusing. Like John said, go with the ensembles during this pattern change that is currently evolving in the upper atmosphere.

I do look at ensembles. I was just stating what the OP GFS was showing. Still hope on the ensembles, keeping a -NAO and a good west based -NAO. EPO goes negative in the 21st-26th range.

[nzucker]

I do look at ensembles. I was just stating what the OP GFS was showing. Still hope on the ensembles, keeping a -NAO and a good west based -NAO. EPO goes negative in the 21st-26th range.

The 18z GFS OP looked great.

[earthlight]

18z GFS also offered some hope with the -NAO bringing in moderate cold and snow chances before XMAS and then a large blocking high developing over the GoA, leading to very cold weather in the long-range, especially over the nation's midsection. The signal for a change in the Pacific has definitely been growing stronger with the last few GFS runs and the 12z ECM also showing heights rises out west at Day 10..

Yeah we're getting there. Things still look pretty encouraging since Doug, myself, and a few others talked about it in more detail last night. Sometimes, it's hard to remember that you aren't going to get snow events immediately during pattern changes like this. Especially in this situation, when we're getting a block that splits off Scandanavian ridging. Although it definitely fits in the "block" category, it's more of a psuedo-blocking ridge that builds into Central Canada...and it's got shortwaves moving all around it..so it's not cut off from the flow like a true "big" block would be.

It doesn't matter though..because it's forecast to keep retrograding west and kick off the changes in the pattern. If it starts hooking up with some ridging poking into the Aleutians...all bets are off. The QBO analogs show a nicely improved Pac and continued above normal heights over blocking areas in January. So I think everything that we're seeing now is a good sign. We're still on track.

[Isotherm]

The next 10-15 days are make or break, and depending upon how they play out (both pattern and sensible weather wise), will ultimately determine the winter we're looking at overall. If the Eastern US mild wx refuses to give up through New Years and we get very little if any snow, then it's probably lights out for a colder/snowier than normal winter this year. December can be a transition month in which a warm first half gives way to a cold/snowy second half, and in those particular years, the winters were pretty good. Or this December can be a front to back torch, in which case any cold/snowy period would probably be 2 weeks or less for this DJF period.

How will it play out? It's very easy to fall into the temptation trap of models, and pull the trigger on canceling a certain period. We have to take a step back, breathe deeply, and look at this objectively here. Have the last 4 runs of any model depicted a similar solution for the events of the coming week? Has a particular model been consistent with its own runs and with the runs of other models? The answer to those questions is no. With that being said, it is becoming more apparent that the inter-run variability is swinging in the direction of a warm/rainy outcome for the Mon/Tues short waves, so now our attention (at least mine) is shifting to the latter part of next week, several days prior to Christmas. The trough does not appear to be digging enough for the early week event and thus the sfc low will probably be developing inland of the Eastern seaboard. Even if it transfers, the mid levels are not cold enough.

So I suggest everyone take a step back, maybe take this weekend off from model tracking, and come back Monday to see what we've got. I'm a believer in sticking to the pattern indicators and analogs until model consensus argues otherwise, so until I see more model agreement regarding the D 4+ time frame, I would not worry just yet. I'm not going to make any more comments concerning how I think January will play out, because 1) I think that's been talked about enough for now, and 2) Most folks are going to be in disbelief given last winter, until we get some kind of snow event. Thus, I'm going to let the next several days play out in the model world and we'll take it from there. The next couple weeks are still very much alive in my opinion.

[Isotherm]

Keep an eye on our Tuesday short wave as it becomes the 50/50 low near Newfoundland, preceding the next wave which is set to arrive about a week from today. Pretty decent mid level ridging progged in SE Canada, and I'd monitor trends in the cold push behind this early week storm and also its movement once offshore. If its speed slows down and/or remains closed off near Newfoundland a bit longer, the ridging to its northwest will continue to hold across sern Canada. This in turn will force an energy transfer from the Mid-west primary to a secondary somewhere off our coastline. So I definitely think this one bears watching

[Snow_Miser]

Keep an eye on our Tuesday short wave as it becomes the 50/50 low near Newfoundland, preceding the next wave which is set to arrive about a week from today. Pretty decent mid level ridging progged in SE Canada, and I'd monitor trends in the cold push behind this early week storm and also its movement once offshore. If its speed slows down and/or remains closed off near Newfoundland a bit longer, the ridging to its northwest will continue to hold across sern Canada. This in turn will force an energy transfer from the Mid-west primary to a secondary somewhere off our coastline. So I definitely think this one bears watching

The 00z GFS has this seconday transfer with the next wave a week from today, but it's about 200 miles to our north. The idea is there, and I'm sure we'll see more changes with the models as we approach this event.

[PB GFI]

We dont get into the cold air until next weekend , there isn`t any kind of block until then , anything that comes our way in the form of ( 3 wave ) will do so through 40 - 50 degress surface temps all week .

Look for pattern to at least start to look better from that time frame on , but not before .

[MJO812]

We dont get into the cold air until next weekend , there isn`t any kind of block until then , anything that comes our way in the form of ( 3 wave ) will do so through 40 - 50 degress surface temps all week .

Look for pattern to at least start to look better from that time frame on , but not before .

There looks to be a block for the 3rd wave. The question will be if it will be strong enough to suppress this storm. I agree about the cold after the storm. GFS continues with the cold outbreak. The storm around Christmas also keeps showing up. 12/26 on this run.

[IntenseBlizzard2014]

Based on the LRC, the Nor'easter from November 7th, 2012 is suppose to show up again by December 27th, 2012. The form of the storm will be most likely stronger, due to stronger temperature contrast and better blocking.

[bluewave]

I think that the EPO is going to be key in determining what the temperature pattern does here for January.

We'll have to watch the Euro ensemble means for an improvement in the Pacific from what we have

been seeing. The years since 1995 with colder to near normal January temperatures here mostly

had a -EPO ridge building over Alaska. The milder January composite featured a dominant +EPO

pattern.

colder pattern

milder pattern

[Isotherm]

Here's what's slightly disturbing about this December thus far, and this may be a good question for Unc W to answer. We've seen a -2 to -3 SD AO the first 15 days of December - how many cases has that occurred in conjunction w/ a continued torch for the CONUS? It's pretty rare, I know that. Usually when you have a tanking AO, the torch regime doesn't last that long over the US, especially if you've got some kind of -NAO. This is beginning to end up like that disastrous 1952 I showed you guys a few weeks ago, the good old caveat to the winter outlook, in which the mastermind EPO/North Pacific signal is so wretched that is rools the roost, overpowering the -AO and -NAO.

As a result we have this image for the world so far Dec. Note basicially everyone else in the freezer in the nern hemisphere. We're on fire.

[Isotherm]

Chris -- good post. I think we're in agreement that the EPO signal is the most important index for getting arctic air into the CONUS. Heights near AK will be key for whether we see a mediocre January or one to remember.

[bluewave]

Here's what's slightly disturbing about this December thus far, and this may be a good question for Unc W to answer. We've seen a -2 to -3 SD AO the first 15 days of December - how many cases has that occurred in conjunction w/ a continued torch for the CONUS? It's pretty rare, I know that. Usually when you have a tanking AO, the torch regime doesn't last that long over the US, especially if you've got some kind of -NAO. This is beginning to end up like that disastrous 1952 I showed you guys a few weeks ago, the good old caveat to the winter outlook, in which the mastermind EPO/North Pacific signal is so wretched that is rools the roost, overpowering the -AO and -NAO.

As a result we have this image for the world so far Dec. Note basicially everyone else in the freezer in the nern hemisphere. We're on fire.

Tom, you are correct that it's rare to get such mild December temperatures here with this strong

of a blocking pattern in place. The warm start to the month with the steep drop in the AO was

an early signal that this month was going to be different. Most of the time Decembers with average

AO readings of below -1 for the month feature below to near normal temperatures. Decembers

like this are the exception rather than the rule. The Decembers that stand out since 1995 for warm

blocks are 1996 and 2001.

[Isotherm]

Tom, you are correct that it's rare to get such mild December temperatures here with this strong

of a blocking pattern in place. The warm start to the month with the steep drop in the AO was

an early signal that this month was going to be different. Most of the time Decembers with average

AO readings of below -1 for the month feature below to near normal temperatures. Decembers

like this are the exception rather than the rule. The Decembers that stand out since 1995 for warm

blocks are 1996 and 2001.

We just can't catch a break over here in the CONUS, Chris. The rest of the world stole our -AO cold the second half of last winter, and it's happening again this December.

I remember running some correlations awhile back regarding the Pacific/Atlantic influence for each winter month, I recall seeing the Pacific pattern as most correlated to our temps in December. The AO/NAO is more significant in JFM than it is in December, and it probably has to do w/ changing wavelenths as we bottom out into the dead of winter. The first half of December is still a transitional phase from autumnal wavelengths.

[PB GFI]

I have been saying that Dec 20 was the date I believed the pattern would change , thats the good news - it will probably work out .

But heres the bad news .

Day 10 - A new trof gets back into Alaska also Day 10 a new trof rotates back thru Asia

which is telling me that the cold is headed once again to the wrong side of the pole for us .

So I dont think it is long lived pattern change and I wouldnt be shocked if we head back to seeing what we have been seeing now after only a week of colder norms .

You can see the movement in the PAC theres is no movement in terms spiking any ridge into Alaska , in fact its the opposite You can see the trof loop back there .

So thats the boss, The Pac RIDGE has the SE ridge on string when it returns it will pull our troff axis back , and if I am seeing the models right , then the cold shot is transient and doesnt lock off AND THIS PATTERN WILL REPEAT ITSELF after relaxing for a week or so .

[nzucker]

I have been saying that Dec 20 was the date I believed the pattern would change , thats the good news - it will probably work out .

But heres the bad news .

Day 10 - A new trof gets back into Alaska also Day 10 a new trof rotates back thru Asia

which is telling me that the cold is headed once again to the wrong side of the pole for us .

So I dont think it is long lived pattern change and I wouldnt be shocked if we head back to seeing what we have been seeing now after only a week of colder norms .

You can see the movement in the PAC theres is no movement in terms spiking any ridge into Alaska , in fact its the opposite You can see the trof loop back there .

So thats the boss, The Pac RIDGE has the SE ridge on string when it returns it will pull our troff axis back , and if I am seeing the models right , then the cold shot is transient and doesnt lock off AND THIS PATTERN WILL REPEAT ITSELF after relaxing for a week or so .

The 0z ECM actually develops the beginning of a -EPO at Day 10 with a western ridge moving north:

[PB GFI]

The 0z ECM actually develops the beginning of a -EPO at Day 10 with a western ridge moving north:

No thats a snapshot. Gotta stop looking at an individual's day. When u loop u will see the trof coming in. The PAC is a mess. Didn't reshuffle. Just gona refire

[nzucker]

No thats a snapshot. Gotta stop looking at an individual's day. When u loop u will see the trof coming in. The PAC is a mess. Didn't reshuffle. Just gona refire

The 12z GFS also develops an Aleutian Low/Alaska High set-up in the longer range, around the time of the Christmas Nor'easter it shows. So there's definitely some model support for a reshuffling of the Pacific pattern.

[Weathergun]

We have decent MJO signal in phases 1/2 now. So hopefully that lead to improvements in Pacific, in the near future.

[bluewave]

We just can't catch a break over here in the CONUS, Chris. The rest of the world stole our -AO cold the second half of last winter, and it's happening again this December.

I remember running some correlations awhile back regarding the Pacific/Atlantic influence for each winter month, I recall seeing the Pacific pattern as most correlated to our temps in December. The AO/NAO is more significant in JFM than it is in December, and it probably has to do w/ changing wavelenths as we bottom out into the dead of winter. The first half of December is still a transitional phase from autumnal wavelengths.

We usually do better with a -AO in December than we are doing so far this December. Most of the years

in the lower than -1 AO December composite had below normal temps here. I think what happened was that

the El Nino faded too early and there was enough of a cold PDO influence to dominate the Pacific pattern.

You can see that the warmth this December was more of an outlier among the other -1 or lower

-AO Decembers. The Pacific is also usually is more cooperative than we have seen so far this month

for allowing cold and snow chances here.

The -PNA/+EPO combination is pretty much giving the Pacific jet free reign across the U.S.

December -1 or lower -AO composite since 1950

[Dsnowx53]

After the crappy Miller B that won't produce anything here, we are seeing by far the best model images of the winter.