The Pattern Ahead

[ORH_wxman]

WE have been so invested in all these storm threats that keep finding new ways to fail that we haven't had much talk about the long range...

The -NAO has been quite stout and in combo of a little bit of EPO cold air dump has given us a cold regime as was advertised a few weeks ago...through Dec 16th, we've had the following temperature departures:

BOS: -3.2F

ORH: -4.1F

PVD: -3.9F

BDL: -3.9F

Here is the composite 500mb anomalies for the first half of the month

You can see the classic -NAO signature and the EPO ridge up through the Bering Straight....which has given a path for colder air to come into the CONUS...as pretty much everyone east of the Rockies has been below normal. The NAO became even more dominant than many of us first envisioned back 2-3 weeks ago and there has been zero hint of a SE ridge....the general look has been large 5H anomalies over the east coast. Typically, this can be a favorable setup for coastal storms and redeveloping storms...usually of the Miller B variety without a very active STJ and a large PNA ridge. We've certainly seen a few chance, but they haven't worked out. We've seen different orientations of that larger scale pattern above that have found ways to keep us out of the snow....suppression, retrograde pattern that ends up slightly too far north, etc.

What does this mean going forward?

Well f you have been frustrated by this pattern, you will get to take some more shots at it, because it doesn't appear to be going away in the next 2 weeks. The latest GFS ensemble mean has the continuation of the -NAO/-PNA pattern with the Kamchatka/Bering ridge.

You can see the analog dates continue to have some heavy hitters in there, but there's also a few duds.

There are some signs the NAO may try to come back toward neutral beyond New Years, but I am skeptical it happens until we have definitive proof....right now its in a negative-at-any-excuse mode.

[nzucker]

Great post, Will; it seems as if the pattern is almost the polar opposite of expected in a strong Niña following a strong Niño. All of the higher than normal 500mb heights are sitting over the Arctic and Northern Asia/Canada, while the lower than normal 500mb heights are displaced to the mid-latitudes. This means that we don't have the typical SE ridge despite the lack of a STJ to knock down the subtropical high pressure that tends to build in a Niña. Overall, a very interesting regime and one that has produced record cold in Florida as well as widespread -4 to -6F departures along the East Coast and several snowfalls in the mid-Atlantic...also has been a brutal patten in Europe as much of Britain is threatening its coldest December in 300 years of records.

Storm track continues to be our enemy, however. It looks as if the GFS hints at pieces of energy ejecting from the ULL near California and perhaps setting the state for a pseudo-clipper and SW flow event. The mid-week clipper looks to be dead on arrival due to the enormous ULL to our Northeast, but it's possible the Christmas storm may be a real threat as both the 12z ECM and 18z GFS show strong negative 500mb anomalies off the East Coast. The block over Baffin Island retrogrades slightly but not as much as originally forecasted, and we have some colder, more arctic air flowing into the CONUS extending from the block over Northern Alaska/Bering Strait towards the Canadian Prairies, around the NAO block.

[HoarfrostHubb]

Can this type of pattern generate true Arctic air intrusions into the Northeastern US?

It has been cold to he sure, but not really coming from the arctic, is it?

[nzucker]

Wasn't 12/23/61 the beginning of a monster Christmas Eve snowfall?

[HoarfrostHubb]

And Socks-uber met just answered my question.

Thanks!

[ORH_wxman]

Wasn't 12/23/61 the beginning of a monster Christmas Eve snowfall?

Yes it was a huge storm for SNE....even NYC metro did pretty good in it...but Ray's area down through 128 belt got 20".

[CoastalWx]

I think the NAO relaxes, but it shows signs of building back towards the Davis Straits near and after NY.

As the block relaxes and moves east, it could also open the door for colder air to move into the northern tier of the US. Nate was alluding to this. At the same time, models almost have a Nino looking storm over the east with a big ridge in the Rockies, and a confluence zone across the typical area northeast of Nova Scotia. This is the ensemble prog which is a little muted.

Here is the 18z op prog.

With what has happened, I'm not saying any more than what's posted...just that it may be something to look at in a few days.

I think we have a shot of a warm up near NY. The euro ensembles seem to be more bullish indicating some sort of a low to our nw and even the Canadian ensemble seem to try and develop troughing over the MW. The GFS doesn't really latch onto this, so the idea of a brief warmup is not certain, but the EC ensembles have tried to indicate this for a few runs. After that, it seems like we go back to a similar pattern, but that's getting out there. I know the weeklies were trying to hint at more troughing in the MW meaning perhaps some swfe later in January.

[nzucker]

Can this type of pattern generate true Arctic air intrusions into the Northeastern US?

It has been cold to he sure, but not really coming from the arctic, is it?

Nothing can come from the Arctic right now because there is an uber-block over Northern Canada and airmasses have to rotate around that feature, which means the really cold air is pushing back towards Siberia and Northern Europe (check out what's happening in the UK right now, for example)....The expansion of the record-breaking -NAO, combined with an atrocious Pacific that is flooding Canada with milder maritime air, ensures that we can't see an arctic outbreak for a while despite being consistently below normal.

The 12z ECM shows the direction of the cold airmass...note the mildness over Hudson Bay and eastern Canada, and some cross-polar from from the PV over the NP into Europe through eastern Greenland:

[CoastalWx]

Nothing can come from the Arctic right now because there is an uber-block over Northern Canada and airmasses have to rotate around that feature, which means the really cold air is pushing back towards Siberia and Northern Europe (check out what's happening in the UK right now, for example)....The expansion of the record-breaking -NAO, combined with an atrocious Pacific that is flooding Canada with milder maritime air, ensures that we can't see an arctic outbreak for a while despite being consistently below normal.

The 12z ECM shows the direction of the cold airmass...note the mildness over Hudson Bay and eastern Canada, and some cross-polar from from the PV over the NP into Europe through eastern Greenland:

The Pacific isn't the problem for Canada. Unlike last year, we don't have a torch ridge over western Canada. The Block has warmed ctrl and eastern Canada, but I think that changes during the 11-15 day and beyond. Western Canada hasn't been all that warm for the most part....at least not like last year.

[Allsnow]

really nice write-up.....always look foward to ur thoughts.

[CoastalWx]

Can this type of pattern generate true Arctic air intrusions into the Northeastern US?

It has been cold to he sure, but not really coming from the arctic, is it?

With that NAO block, the cold will move around the block and into the Plains, however if the block weakens a little or moves east...look out. That's when we may see more arctic outbreaks, especially if the Pacific cooperates a little.

[nzucker]

The Pacific isn't the problem for Canada. Unlike last year, we don't have a torch ridge over western Canada. The Block has warmed ctrl and eastern Canada, but I think that changes during the 11-15 day and beyond. Western Canada hasn't been all that warm for the most part....at least not like last year.

Oh agreed, certainly not a torch ridge. However, if the Pacific cooperated even more and we get a -EPO block over Alaska, then Canada would be much colder as all the cold anomalies forming over Alaska in the next week would be forced southward. Most of the ridging so far this season has been back towards the Aleutians/Bering Strait, which is keeping much of Canada near average but not bringing any monumental cold down.

[ORH_wxman]

The Pacific isn't the problem for Canada. Unlike last year, we don't have a torch ridge over western Canada. The Block has warmed ctrl and eastern Canada, but I think that changes during the 11-15 day and beyond. Western Canada hasn't been all that warm for the most part....at least not like last year.

Yeah Canada has generally been fine...the Kamchatka/Bering ridge allows for NW Canada to get cold along with AK vs a vortex there which torches NW Canada for the most part. Then chunks of that cold get rotated down from time to time keeping us from seeing those awful torches like 1998, 1999, 2006, etc.

[Damage In Tolland]

I hope you guys are right and Donny baseball Sutherland is wrong. He's torching and ridging us for much of Jan and Feb

[ORH_wxman]

I hope you guys are right and Donny baseball Sutherland is wrong. He's torching and ridging us for much of Jan and Feb

Well this thread isn't really about January and February...maybe really early January I mentioned in here.

[CoastalWx]

Oh agreed, certainly not a torch ridge. However, if the Pacific cooperated even more and we get a -EPO block over Alaska, then Canada would be much colder as all the cold anomalies forming over Alaska in the next week would be forced southward. Most of the ridging so far this season has been back towards the Aleutians/Bering Strait, which is keeping much of Canada near average but not bringing any monumental cold down.

I think western Canada will cool off once this block goes east. At that point, it's possible that we may see troughing develop in the Plains and Midwest...perhaps similar to the cold outbreak that they had in November. That may be the point were sne warm for a few days, but could also mean swfe since we are later into the season. Of course it's speculation at this point, but I could see that. Don S would argue for a pattern change with the AO going +, but it almost seems to battle the nao which tries to stay somewhat - and even build back into the Davis Straits.

[Damage In Tolland]

Well this thread isn't really about January and February...maybe really early January I mentioned in here.

Right..but the point is we'd have to see a pretty quick flip and turnaround from this pattern to what he is calling for. Hopefully he's wrong. The only thing that scares me is he's never wrong

[CoastalWx]

Right..but the point is we'd have to see a pretty quick flip and turnaround from this pattern to what he is calling for. Hopefully he's wrong. The only thing that scares me is he's never wrong

Well there is a difference between torch ridge and some above normal temps. I certainly would not be shocked for temps that are warmer than normal, but it doesn't have to mean a torch. That said, I haven't done the research he has, but I think a weak +AO would be fine for us.

[Ginx snewx]

Right..but the point is we'd have to see a pretty quick flip and turnaround from this pattern to what he is calling for. Hopefully he's wrong. The only thing that scares me is he's never wrong

Don is off the hook great but he was very wrong for late Feb and March last winter. I followed his thoughts last year and am wondering why he is not calling for the AO to rebound negative like his last years stats said. That being said if we flip positive strongly then I will spread your ashes over heavy heavy snow in the Arctic.

[donsutherland1]

For purposes of clarification, here's my thinking:

Using the La Niña-Severe December Blocking analogs, January would likely see milder anomalies overspread the eastern half of the U.S., with the month winding up warmer than normal. The best timing for the start of that trend would be during the first week of January +/- a few days. Before then, troughing should remain frequent in the East. One or two moderate snowfalls are possible before the pattern change, though I believe odds are against any KU-type storm.

February could wind up becoming the warmest month relative to normal, but blockiness and cold could return late in the month, especially if a new severe blocking regime develops as happened in Winter 2000-01 (and I do believe there will be another round of such blocking at some point this winter, but the big question is when). In fact, the monthly AO figure for the 1950-51, 1995-96, and 2000-01 winters was below -1.4 in all of those cases for March. Hence, March would likely wind up on the cold side of normal (if renewed blocking develops).

The milder regime that I expect to unfold in January does not necessarily mean a sustained, all-out blowtorch. I do believe the risk of some days with excessive warmth will be greatest late in January and probably early in February. A positive NAO would very likely accompany any excessive warmth.

Last year, I was quite confident that severe blocking would redevelop late January/early February. Unfortunately, during La Niñas, especially moderate ones, severe blocking episodes have typically been shorter, less frequent, and more widely spaced.

Finally, the problem in March was that the last round of severe blocking collapsed sooner than I had expected. Hence, the cold was routed and little snowfall was recorded.

[nzucker]

I think western Canada will cool off once this block goes east. At that point, it's possible that we may see troughing develop in the Plains and Midwest...perhaps similar to the cold outbreak that they had in November. That may be the point were sne warm for a few days, but could also mean swfe since we are later into the season. Of course it's speculation at this point, but I could see that. Don S would argue for a pattern change with the AO going +, but it almost seems to battle the nao which tries to stay somewhat - and even build back into the Davis Straits.

Certainly agreed, as the signal for a more intense ridge over Kamchatka/Bering Strait means that cold air flows from Alaska into NW Canada...you can see the bubbles of -30C over parts of the North Slope and Yukon that the GFS has been breaking out. I think this will lead to a broad trough over the CONUS with a potential double block scenario as the NAO reforms over Davis Strait/Baffin Island (never really broke down there) and the ridge over Kamchatka trying to pinch the PV off towards Canada. We will have to deal with more of a +AO look as the high-latitude blocking moderates but I'm still thinking a good chunk of the CONUS stays below average, including SNE/NYC.

Right..but the point is we'd have to see a pretty quick flip and turnaround from this pattern to what he is calling for. Hopefully he's wrong. The only thing that scares me is he's never wrong

The 12z ECM does show a mega +AO develop with a huge polar low sitting over the North Pole:

[Go Kart Mozart]

The 12z ECM does show a mega +AO develop with a huge polar low sitting over the North Pole:

With the growing Kamchatka and NAO blocks shown, I would think that the +AO would be short-lived. Maybe that vortex over the pole gets squeezed into Canada?

[cpickett79]

With the growing Kamchatka and NAO blocks shown, I would think that the +AO would be short-lived. Maybe that vortex over the pole gets squeezed into Canada?

DON S shows NAO blocking going positive by end of first week in january. prob will be mid january but that thaw should last thru a good chunk during which we aveage our coldest anomalies......get ready for cutters by mid january .....cutters galore.

so cold till then enjoy! maybe a christmas snow....more like a medium event then cold and another shot for some precip i think the shot of having a really anomalous winter of low snow is very much on the table. not saying DJFM will average torchlike either but i think jan 10- feb 10 will ave +4 for SNE. and more so for mid atlantic.

[nzucker]

With the growing Kamchatka and NAO blocks shown, I would think that the +AO would be short-lived. Maybe that vortex over the pole gets squeezed into Canada?

Yeah agreed...if that ridge can amplify any more, Canada would get very cold as the polar vortex becomes trapped between the Kamchatka block and high height field left behind from the NAO...it would have to drop into the Canadian Archipelago and then would eventually migrate colder air into the Canadian Prairies/Northern Plains.

[Ginx snewx]

Cold appeal continues on all models nice. Christmas night storm looms large, models vary in location per standard but overall we are still in the game late first quarter. I still expect a high scoring game.

[weathafella]

Cold appeal continues on all models nice. Christmas night storm looms large, models vary in location per standard but overall we are still in the game late first quarter. I still expect a high scoring game.

Here's something anecdotal. My wife is going to Chicago Xmas day and will return the late night of 12/26. The last time she left in the winter was 1/19/05 and she stayed for a week. The time before that was 3 days before PD2 and she returned the day after. Keep hope alive.

[ORH_wxman]

As we continue to look at the pattern in the longer range toward New Years....the analog composite is still pretty bullish on some events. Almost every date on there had an avisory event or better within a couple days of it.

The analog composite has more ridging in the Davis straight/Baffin Island region than the ensemble verbatim, but there's probably a reason for that....models will tend to break it down there much faster than what actually happens.

In terms of very large events...the two 1961 dates at the top are sandwiched around a widespread 12"+ storm for SNE. A few days after the 1976 date there was a pretty large event too...BOS had over 12".

[A-L-E-X]

I think most of us would love for a 1961-esque pattern development.

[nzucker]

The analog composite has more ridging in the Davis straight/Baffin Island region than the ensemble verbatim, but there's probably a reason for that....models will tend to break it down there much faster than what actually happens.

12z ECM dissolves the impressive NAO block around Day 6, although there's still a high height field left near Baffin Island. The NAO looks to become more positive although ridging is starting to form in the Atlantic at Day 10, and a Rex block may be developing as an ULL tries to slide eastward towards the Mediterranean. The pattern seems to be very persistent in that the NAO never breaks down for more than a few days. We're also starting to get some help from the PAC in terms of a +PNA pattern with the ridge over the West connection with the high pressure near Baffin Island.

[Ginx snewx]

12z ECM dissolves the impressive NAO block around Day 6, although there's still a high height field left near Baffin Island. The NAO looks to become more positive although ridging is starting to form in the Atlantic at Day 10, and a Rex block may be developing as an ULL tries to slide eastward towards the Mediterranean. The pattern seems to be very persistent in that the NAO never breaks down for more than a few days. We're also starting to get some help from the PAC in terms of a +PNA pattern with the ridge over the West connection with the high pressure near Baffin Island.

As we thought