Evidence for global regime shift mounting

[CoastalWx]

We've got the first attempts at a phase 7-8 MJO by early January. Key word here "attempt" but it would make sense if its coinciding with a global pattern change.

I don't buy that. The bias corrected stuff goes right back into the COD and other progs go towards phase 4 again.

[Isotherm]

I don't buy that. The bias corrected stuff goes right back into the COD and other progs go towards phase 4 again.

Agree, that's why I said attempt. ECMWF keeps it in COD, but I don't think the MJO is necessary to change this pattern.

[ORH_wxman]

Until there is good evidence that the warming that high up starts to downwell, its not going to change anything. There are some hints maybe it starts doing that in early January...but even if it does, the effects wouldn't be felt on us until at least a couple weeks later.

[Weathergun]

I don't buy that. The bias corrected stuff goes right back into the COD and other progs go towards phase 4 again.

The MJO forecasts have been too weak though. I think sometime next month, it could go into somewhere between phases 6 and 7 again. Before collapsing or looping around again. Especially if the easterly 850mb winds near the dateline, diminish.

[Alpha5]

that is stratospheric warming? creating a +pna? looks to stilll be expanding. What is the lag time?

Thats at 50mb not 500mb. I think its depicting a MT event which kicks off the stratospheric warming in the arctic. As Tom eluded to in an earlier post, the effects take a while to be felt, but somewhere around the first 10 days of January, we should see changes.

[Isotherm]

Time to revisit the ideas put forth in the original post. The period in question for the beginning of the pattern/regime shift was early January, possibly as late as the second week of January. Looking ahead, the next 3-7 days will feature a transient cold shot followed by moderation late week. Given the warmth to start January, Jan 1-7 period will probably finish near or slightly above normal temp wise even w/ the arctic air Tues-Wed.

However, fundamental shifts in the regime should take hold shortly thereafter, and I think January 10th is the magic date looking back on this post from a few weeks ago. This marks the onset of true arctic air getting on the playing field, as the dreaded Alaskan vortex finally gets displaced, and a negative EPO configuration initiates by about Jan 9th-10th. Thereafter, arctic air will engulf much of the nation in a WSW-ENE fashion, with resistance in the SE due to a continued +NAO signal.

With that being said, I'm still sticking w/ my original idea for the +AO regime to end over the next week.

EP vectors have turned poleward over the past 7-10 days indicating upward planetary wave propagation into the stratosphere, a weakening of the polar night jet, and a gradual disturbance/displacement of the arctic polar vortex should follow suit.

ECMWF forecasts continue to indicate polward EP flux into the middle of January, which bodes well, and coincides with the latest ensemble guidance for a decline into the negative modality of the AO post January 10th...yes, that's right...I actually said negative.

The NAO will be more stubborn. Heights rise across the arctic first, along with the development of the negative EPO by Jan 10th, getting pos anomalies into Alaska/western Canada. This pattern change is key because is cuts off mild Pacific air and initiates cross-polar flow, creating a nice upper level transport from NW Canada/Siberia into the United States.

So I expect Jan 10-20 to feature a developing neg EPO, and neg AO. The issue becomes the PNA and NAO during this period. The former may be trending negative, with lower heights in the West, with the NAO still positive, the Southeast will be warmer than normal, and the baroclinic zone probably draped across the NYC/PHL metro regions. I think New England folks should be happy as clams now as this type of regime through the 20th is favorable for good snows there. I think our area will also get in on snow in the Jan 10-20 period, with probably a continued bad snow pattern for those south of us, as long as the NAO remains positive.

John (earthlight) mentioned the Jan 9th potential last night and I also agree that has to be monitored due to the PNA spike; however, in terms of real, more sustained polar/arctic air getting into the picture, that will occur post Jan 10th.

So I see Jan 9th as the first threat in the new pattern, with increasingly favorable opportunities thereafter, and undoubtedly, this pattern is significantly better than December (Although thats not saying a lot).

[Hailstorm]

Time to revisit the ideas put forth in the original post. The period in question for the beginning of the pattern/regime shift was early January, possibly as late as the second week of January. Looking ahead, the next 3-7 days will feature a transient cold shot followed by moderation late week. Given the warmth to start January, Jan 1-7 period will probably finish near or slightly above normal temp wise even w/ the arctic air Tues-Wed.

However, fundamental shifts in the regime should take hold shortly thereafter, and I think January 10th is the magic date looking back on this post from a few weeks ago. This marks the onset of true arctic air getting on the playing field, as the dreaded Alaskan vortex finally gets displaced, and a negative EPO configuration initiates by about Jan 9th-10th. Thereafter, arctic air will engulf much of the nation in a WSW-ENE fashion, with resistance in the SE due to a continued +NAO signal.

With that being said, I'm still sticking w/ my original idea for the +AO regime to end over the next week.

EP vectors have turned poleward over the past 7-10 days indicating upward planetary wave propagation into the stratosphere, a weakening of the polar night jet, and a gradual disturbance/displacement of the arctic polar vortex should follow suit.

ECMWF forecasts continue to indicate polward EP flux into the middle of January, which bodes well, and coincides with the latest ensemble guidance for a decline into the negative modality of the AO post January 10th...yes, that's right...I actually said negative.

The NAO will be more stubborn. Heights rise across the arctic first, along with the development of the negative EPO by Jan 10th, getting pos anomalies into Alaska/western Canada. This pattern change is key because is cuts off mild Pacific air and initiates cross-polar flow, creating a nice upper level transport from NW Canada/Siberia into the United States.

So I expect Jan 10-20 to feature a developing neg EPO, and neg AO. The issue becomes the PNA and NAO during this period. The former may be trending negative, with lower heights in the West, with the NAO still positive, the Southeast will be warmer than normal, and the baroclinic zone probably draped across the NYC/PHL metro regions. I think New England folks should be happy as clams now as this type of regime through the 20th is favorable for good snows there. I think our area will also get in on snow in the Jan 10-20 period, with probably a continued bad snow pattern for those south of us, as long as the NAO remains positive.

John (earthlight) mentioned the Jan 9th potential last night and I also agree that has to be monitored due to the PNA spike; however, in terms of real, more sustained polar/arctic air getting into the picture, that will occur post Jan 10th.

So I see Jan 9th as the first threat in the new pattern, with increasingly favorable opportunities thereafter, and undoubtedly, this pattern is significantly better than December (Although thats not saying a lot).

Very nice post. Although, not only do we need to see the weakening of the polar night jet, but we also need to see a reversal in the wind anomalies at 30 mb in order for the warming to fully propagate downward. Currently, we do not see such a reversal taking place. Do you think we will begin to see hints of this happening in the near future?However, the solar index values continue to decline, which goes excellent in tandem with an east-based -QBO.

[Isotherm]

Very nice post. Although, not only do we need to see the weakening of the polar night jet, but we also need to see a reversal in the wind anomalies at 30 mb in order for the warming to fully propagate downward. Currently, we do not see such a reversal taking place. Do you think we will begin to see hints of this happening in the near future?However, the solar index values continue to decline, which goes excellent in tandem with an east-based -QBO.

Hailstorm, thanks for the post, just saw it now. I agree w/ your thoughts. I think we'll be seeing the reversal in those anomalies take place soon, as we see another pulse of warming which will try to propagate further down through the stratosphere. The warming in the mid/upper stratosphere has already weakened the tropospheric vortex, and it's apparent to me that we'll see a further weakening from this point forward. The re-structuring of the global regime will be occurring this week as we see the Alaskan vortex loosen its grip, and a -EPO/ridge extension to the pole initiate. Low solar values over the past few weeks also argue for the strat warming event to propagate downward. In addition, east QBO episodes are more favorable for blocking regimes in the second half of winter.

Given the evolution on latest modelling, I have no reason to change my thinking that January 10th beyond we're looking at a much different pattern (the pattern change is already starting now).

[Isotherm]

Latest QBO data suggests we're now flipping to easterly down to 40, 45, and likely 50mb. December's data is down near neutral for 50mb. This shift will only aid the strat warming event in its propagation downward, and the reversal to negative AO which should occur within the next week. Whether the NAO immediately follows suit is the question for the day - models are struggling on that aspect - one run producing extensive high lat blocking, the next, more low heights over Greenland. Right now I think it's safe to say the negative EPO and negative AO are probable in the medium range. A negative NAO will probably follow about 7-10 days after.

[earthlight]

This post is really meant to try and add some things...and update on some things...but I think Tom has covered the bases pretty nicely in his last several posts. After reading some of the QBO and other pattern change stuff which he has covered...we can see that changes are here.

The pattern change is happening -- I don't think that there is any way to argue that at this point in time. Things began to change from the top at the end of December, when dramatic warming occurred at 5hpa. We went from below normal (79-08 values) to near record-high levels in a two week span. And while the 5hpa temperature doesn't have a dramatic impact on the pattern down the road, it signaled the kick off of a pattern change which has now been set into motion by an increasingly moderate stratospheric warming event. While this event may not necessarily be classified as "SSW", it definitely is going to be sufficient to change the pattern.

The changes in the Pacific are easily visible on almost all guidance, with a large ridge building from the Aleutian Islands, towards the Beufort Sea and even extending eastward towards Baffin Island. On the other side of this could, hypothetically, be a -PNA trough which forms from Western Canada to the Northwest US. Such a regime would likely support a gradient pattern across the entire CONUS with the cold air ejecting eastward, battling with the Southeast Ridge. The thermal gradient that would result could support numerous overrunning events.

However, the problem doesn't end here -- we also need to carefully watch what happens with the Atlantic and the Polar Vortex. Because while the Pacific changes are good, the Atlantic remaining so unfavorable would more than likely cause significant problems down the road anyway. In this case, we need to see a downwelling of the warming which has been observed at 5, 10, and 30 hpa. Such an event could hypothetically reposition or split the anomalous Polar Vortex which has been in place over Greenland and the Davis Straight.

The 12z Euro was impressive in showing such an event down to 70 hpa, and we have seen this for a few runs in a row now. The image below illustrates the changes modeled at 240 hours -- with the link to the 24 hour forecast directly above it. You can see the model is forecasting a dramatic change to the orientation of the pattern.

24 hour forecast : http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwf70f24.gif

240 hr forecast:

In addition to this, the GFS Ensembles have begun to catch on to such an idea over the last several days with the Polar Vortex (or the greatest negative 500mb height anomalies associated with it) retrograding into Central Canada. Such an event is likely being modeled a bit too early (although there is always some degree of variance), and it is important to remember that these can take two/three weeks to downwell and affect our pattern.

Where we go from here is still uncertain -- and it is prudent to watch very carefully over the next week or two. I wouldn't be surprised if, in the end, we wind up closing out January with a gradient type pattern and a -PNA. But where that gradient sets up is a complete toss up -- and more often than not, our area winds up being the battle ground. Beyond this, we can hope that the ECMWF stratospheric ideas are correct...and if they are, we could begin to see the return of high latitude ridging in the NAO region.

So stick it out over the next week or two. Although I can't promise you snow, I can promise that two weeks from now the pattern will be a hell of a lot more active, with more chances and more fun than we are having right now. With the changes in motion, it's our job as forecasters to watch, assess, diagnose, and forecast the effects from here. So, I think it's worth saying for the first time this winter....."here we go.."

[Ray8002]

Nice write up John.. You the man.

[Isotherm]

John,

Great post as usual. No doubt we're seeing the global regime shifts occur as we speak, with the AO taking left, right, upper jabs, and kicks to the gut. It's being bruised and weakened right now, but won't be completely knocked out for another week or so.

The only thing I'd add is I'm interested in the January 12th-15th period as holding decent potential. Ensembles have been fairly consistent in major trough amplification coinciding w/ a PNA spike as well as heights rising in the arctic.

If this type of meridional depiction comes to frution, with the Western ridge extending into NW Canada, we're likely going to see cyclogenesis of some sort in the Eastern US. In terms of getting accumulating snow, the pattern mid/late next week is sufficient. If it doesn't produce anything, the pattern afterwards will continue to improve in terms of high latitude blocking as you've nicely described.

[earthlight]

Regarding the above noted threat...I think there is some limited potential, but also some notable deception at first glance. When you look at the 500mb charts, you can see that although the height anomalies are rather severe, the trough which could produce cyclogenesis on the east coast is flat. The very robust shortwave ejecting from the Southern US a day or so prior to this sweeps the baroclinic zone offshore...and the flow takes a while to recover. That essentially ruins any chance for a monster storm to develop, unless the modeled trough over the Great Lakes was to amplify farther west near the Plains and then sweep east. Such an event is not impossible given the ridge on the West coast, but is definitely made less likely by the events which transpire prior to it.

http://www.meteo.psu.edu/~gadomski/AVN_12z/f180.gif

[Isotherm]

Regarding the above noted threat...I think there is some limited potential, but also some notable deception at first glance. When you look at the 500mb charts, you can see that although the height anomalies are rather severe, the trough which could produce cyclogenesis on the east coast is flat. The very robust shortwave ejecting from the Southern US a day or so prior to this sweeps the baroclinic zone offshore...and the flow takes a while to recover. That essentially ruins any chance for a monster storm to develop, unless the modeled trough over the Great Lakes was to amplify farther west near the Plains and then sweep east. Such an event is not impossible given the ridge on the West coast, but is definitely made less likely by the events which transpire prior to it.

http://www.meteo.psu...VN_12z/f180.gif

Agree, the trough does not look impressive at this time, and ideally we'd like to see this early week warm storm cut further inland so that the baroclinic zone is aligned along the EC immediately after. As it stands now, the sern s/w rides the east coast and pulls the trough axis eastward too quickly for anything of significance to get going. However, it's something to watch given the strong ridge out West.

[NJwinter23]

John,

Great post as usual. No doubt we're seeing the global regime shifts occur as we speak, with the AO taking left, right, upper jabs, and kicks to the gut. It's being bruised and weakened right now, but won't be completely knocked out for another week or so.

The only thing I'd add is I'm interested in the January 12th-15th period as holding decent potential. Ensembles have been fairly consistent in major trough amplification coinciding w/ a PNA spike as well as heights rising in the arctic.

If this type of meridional depiction comes to frution, with the Western ridge extending into NW Canada, we're likely going to see cyclogenesis of some sort in the Eastern US. In terms of getting accumulating snow, the pattern mid/late next week is sufficient. If it doesn't produce anything, the pattern afterwards will continue to improve in terms of high latitude blocking as you've nicely described.

It's unfortunate that this trough amplification is really highlighted by the southern shortwave that brings us our rainstorm on the 12th, followed by the cold wave. I was hopeful that a second wave might try to dive down into the trough a couple of days afterward with the +PNA, cold air in place and our 1/12 rainstorm phased into a vortex causing a brief transient NAO ridge.. not seeing much support for that today..but then again, that 1/12 storm is going to continue to cause havoc with the models and will have major implications on the future pattern.

[earthlight]

A few of the GEFS members are trying to amplify the second shortwave behind the main cutoff which swings through our area.

http://www.meteo.psu.edu/~gadomski/ENSPRSNE_12z/f180.gif

[CoastalWx]

I still think the NAO will avg positive through the month. Hopefully Feb it flips.

[MJO812]

You know things are not going well when the last post was from Jan 6.