Evidence for global regime shift mounting

[Isotherm]

http://www.lightinthestorm.com/

My latest discussion on the pattern going forward, why I think the blocking has been delayed thus far, and more.

As we make our way into the 3rd week of December, temperature departures so far this month look like this:

The colder than normal December is verifying for the majority of the country; however, many in the Northeast and Mid-atlantic are beginning to wonder, will winter ever show up this year? While we have seen some transient shots of cold air – one such airmass overhead right now – there hasn’t been any sustained, well below normal air over the Northeastern part of the US. The pattern thus far as been conducive for the development of Western/Central US troughs, via the very low height field encompassing the Arctic and North Atlantic. The slightly favorable North Pacific regime – a +PNA/-EPO – has allowed for some jet bucking in the East, but for the most part it’s been a “dangle the carrot tease” type of pattern. The bulk of the polar/arctic air has remained locked up over the northern plains and Canada.

As long as we continue to see a low height field in the Arctic/north atlantic (+NAO/+AO), it will be difficult to achieve sustained colder than normal temps and/or snowstorm threats in the Northeast corridor. The slightly positive PNA will persist for the next couple weeks, so that will at least force some cold air into the northern tier, creating a tight west to east baroclinic zone from the Plains into the Northeast, aka a gradient pattern. Good examples of gradient patterns are December 2007 and December 2008 – both Nina years – and both featuring many southwest flow events, that is, storms moving SW-NE along the tight thermal boundary separating the relative warmth over the Southeastern US from the relative chill over New England. The NYC metro area will find itself in this battleground zone for the next couple weeks, and with any luck, that zone will shift far enough south to perhaps provide a white Christmas for parts of the area. I’m more confident on areas NW of NYC seeing accumulting snow before Christmas – as far as the coast – I don’t believe the global regime shift will have responded to impact sensible weather just yet. Is it possible to get a white Christmas on the coast? Yes, but we need to hope for a temporary shift south in the Canadian Polar vortex, to force that baroclinic zone safely south of our region.

An illustration of our pattern through Christmas. This is the ECMWF H5 map for days 8-10.

So for the NYC area and the coastal corridor from DCA-BOS, anticipate a fairly typical Nina pattern through week 2, including rain events followed by shots of polar air, averaging out near normal temp wise overall.

Now, beyond that time frame – there is controversy as to whether blocking will ever show up this winter. As I’ve stated a few times since my winter outlook this fall, the question for me is not IF the blocking will show up, but WHEN. Initially, a few months ago, I thought it’d be December into the first half of January, but now I believe it will be the end of December through most of January, and I’m going to explain why (I think) the original time frame likely failed.

Note in the following image, the Solar cycle Ap index progression with the purple dots denoting monthly values. Geomagnetic activity has generally been below 10 since 2007, but in the Sep-Oct period, we saw a surge in activity up near 15 which likely aided in the development of a strongly positive +AO/NAO regime for the month of November into early December. However, notice how last year, we had a drop off in values just prior to December, preceding the major NAO blocking event. This year we have the same, but geomag activity has been much higher this autumn compared to last autumn. With that said, considering values have now been consistently below 5 over the past month, the tropospheric response should occur sooner rather than later.

Furthermore, solar flux was high in the Oct-early Nov period, relative to recent years, which added fuel to the fire in terms of +AO/NAO maintenance.

Solar flux is now falling down from its peak near 180 to around 140 now, and sunspot number (less important for blocking) is also falling.

While this has delayed the blocking thus far, as noted above, current values on both the geomagnetic and solar flux data suggest an initiation of negative AO and NAO fairly shortly (by the end of this month).

Stratospheric conditions will also be changing over the next few weeks, with a slow but steady warming of the 10mb-50mb layers initiating in Eastern Asia/north pacific and eventually propagating northward towards Alaska and into the Arctic Circle. I’m utiziling the potential warming event as another factor for the blocking, but if a major warming does not happen, I don’t believe that’s necessary for the NAO and AO to turn negative by the end of this month into January.

Now – 50hPa:

240hrs later – 50hPa:

Note the brighter oranges developing near Alaska, indicative of a warming occurring. At this point, the warming has not spread over the entire Arctic, but it is a definite step in the right direction, which should take another 1-2 weeks to fully realize (meaning the full warming probably taking at least 3 weeks to materialize).

So how will our sensible weather be impacted?

Bottom lines:

1) The next 2 weeks – through Christmas – anticipate a gradient pattern with storms favoring the interior Northeast. Temperatures will average out near/slightly below normal with surges of mild air ahead of inland tracking lows and surges of polar air following these same lows. Essentially we’re talking a back and forth temp regime with precip chances every several days or so.

2) The onset of a global regime change should initiate by week 2, as geomagnetic and solar flux values argue for a height rise across the top of the globe. This argument is further strengthened if a stratospheric warming event occurs, the signs of which are showing up now – warming spreading from the north pacific into Alaska and the arctic circle.

3) Negative AO and NAO development by week 3, after Christmas and around New Years. Due to the delayed initiation of the blocking, January could be a much colder month than forecasted in the winter outlook. Whether it persists into February depends upon its initiation time frame. Obviously a later change to persistent colder weather would mean February could be interesting.

4) White Christmas likely for the interior Northeast – up for grabs in the I-95 corridor. If we can get the polar vortex to force a low tracking south of the region, then maybe, but I wouldn’t get my hopes up given the full realization of the new NAO/AO regime shouldn’t occur until after Christmas.

5) December will finish colder than normal for most of the country, save for the Northeast/Lakes, due to the excessive warmth we’ve seen thus far, it will be difficult to erase those departures (unless we can get major cold into our area by the last week of December, which cannot be ruled out).

The main point to underline is the next 1-2 weeks are a continuation of the Nina regimes (back and forth), week 2 into 3 is a transition period (Christmas), and much more interesting pattern should unfold thereafter.

[MJO812]

Great writeup. If that means a cold and snowy Jan and Feb, bring it on

[NYCSuburbs]

Nice write up! Although late Dec/early Jan may very well be a reasonable time frame for any pattern change, do you see any possibility that it would be delayed beyond late December? I'm hoping myself for a late December change but with the way things have been going so far, I'm not too sure.

[CoastalWx]

Good read, you always put forth great stuff. The euro also tries to get a little warming near d10 too.

[Sundog]

Fantastic read. Signs are pointing better times ahead.

[Ottawa Blizzard]

Great writeup! Do you see any potential for a 93-94 type pattern? The pattern that year changed between Christmas and New Years, sort of like what you're hinting may happen this year.

[earthlight]

Tom, great post. In thorough agreement especially through the first two weeks of your forecast to around the Christmas Holiday. The gradient pattern has been well advertised in this range on most global ensemble suites through the last week or so of the month. I do think that there is the potential to sneak something in (likely something small and/or invovling some snow before a changeover) if we can establish some of the cold air from the higher latitudes. The ensemble guidance has been showing some poorly timed intrusions of arctic air--but in such an active pattern with energy streaming Northeast from the Southwestern United States, you never know exactly when you might get a weak to moderate perturbation to force some precipitation underneath the dome of cold air.

Moving forward--I think we are finally starting to see some of the changes that we have been looking for towards the end of the month. The CPC 05hPa temperature map has shown a weak spike over the past week or so. It's not anything wildly encouraging, but we are still running well below the mean so it is a good sign to see some warming here. I included the graphic below. Note that right around this time is usually when we start to see changes to the temperature.

The ECMWF has also recently begun to show some cracks in the armor in regards to movement and change of the stratospheric vortex. We're looking at +240hr forecast here--so a bit of caution is definitely prudent, but the changes definitely need to be noted through the end of the period.

Initial: http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwf70a12.gif

The MJO looks to be unfavorable on most global ensemble guidance through around the beginning of January -- but I've begun to lose some faith in ensemble forecasting for the MJO impulses over the past several weeks. They have been highly innacurate and don't offer much of a good look into where things are going. We recently had a moderate impulse a few weeks ago which brought us through Phase 5. The forecast models are still trying to weaken the MJO into the COD and then loop back towards Phases 4-5-6 as we go into the New Year. Such a turn of events would be somewhat unfavorable -- but with the changes to the stratospheric vortex at least allowing some room for high latitude blocking -- we would definitely be better off at that point than we are now.

[Alpha5]

Very good read. Could you explain how a decline in solar flux and geomagnetic activity leads to a better chance of blocking?

[Alpha5]

Tom, great post. In thorough agreement especially through the first two weeks of your forecast to around the Christmas Holiday. The gradient pattern has been well advertised in this range on most global ensemble suites through the last week or so of the month. I do think that there is the potential to sneak something in (likely something small and/or invovling some snow before a changeover) if we can establish some of the cold air from the higher latitudes. The ensemble guidance has been showing some poorly timed intrusions of arctic air--but in such an active pattern with energy streaming Northeast from the Southwestern United States, you never know exactly when you might get a weak to moderate perturbation to force some precipitation underneath the dome of cold air.

Moving forward--I think we are finally starting to see some of the changes that we have been looking for towards the end of the month. The CPC 05hPa temperature map has shown a weak spike over the past week or so. It's not anything wildly encouraging, but we are still running well below the mean so it is a good sign to see some warming here. I included the graphic below. Note that right around this time is usually when we start to see changes to the temperature.

The ECMWF has also recently begun to show some cracks in the armor in regards to movement and change of the stratospheric vortex. We're looking at +240hr forecast here--so a bit of caution is definitely prudent, but the changes definitely need to be noted through the end of the period.

Initial: http://wekuw.met.fu-.../ecmwf70a12.gif

The MJO looks to be unfavorable on most global ensemble guidance through around the beginning of January -- but I've begun to lose some faith in ensemble forecasting for the MJO impulses over the past several weeks. They have been highly innacurate and don't offer much of a good look into where things are going. We recently had a moderate impulse a few weeks ago which brought us through Phase 5. The forecast models are still trying to weaken the MJO into the COD and then loop back towards Phases 4-5-6 as we go into the New Year. Such a turn of events would be somewhat unfavorable -- but with the changes to the stratospheric vortex at least allowing some room for high latitude blocking -- we would definitely be better off at that point than we are now.

hey john where do you get those ECMWF maps?

[CoastalWx]

I honestly think we are going to have to wait until the beginning of January for anything notable wrt blocking and probably mid month or so, but I sure hope it can be earlier.

[earthlight]

I honestly think we are going to have to wait until the beginning of January for anything notable wrt blocking and probably mid month or so, but I sure hope it can be earlier.

Yeah I definitely agree with that idea. The stratospheric and QBO changes are just beginning, and can often have a pretty significant lag (in terms of short to medium term weather impacts). The first-second week of January lines up well with the tail end of the MJO forecasts which are trying to show some signs of improvement by then.

[Alpha5]

hey john where do you get those ECMWF maps?

bump for general knowledge on Euro stratosphere maps

[earthlight]

bump for general knowledge on Euro stratosphere maps

http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ec.php?alert=1&level=70&forecast=all&lng=eng#fig11

[TheTrials]

Yeah I definitely agree with that idea. The stratospheric and QBO changes are just beginning, and can often have a pretty significant lag (in terms of short to medium term weather impacts). The first-second week of January lines up well with the tail end of the MJO forecasts which are trying to show some signs of improvement by then.

you and I have agreed on this since right around thanksgiving.

[tornadojay]

Excellent Write-up!

[NorEaster27]

nice writeup, but I dont expect much changes for another month or so, hopefully its sooner. I agree it will be quicker for the interior NE, upstate NY to NNE

[Dark Energy]

Great job in the OP!

[easternsnowman]

This has been the best desciption of what has happened and what many of us think will happen on this board.

[Snow_Miser]

Interestingly today at the 1 hPa level there is some stratospheric warming starting to take shape in the Arctic Basin, possibly associated with the increasingly negative QBO.

The ECMWF and the GFS both show a SSW in the coming days, so seeing the statospheric layer warming in the Arctic Basin is definitely encouraging for a pattern change to say the very least.

[earthlight]

nice writeup, but I dont expect much changes for another month or so, hopefully its sooner. I agree it will be quicker for the interior NE, upstate NY to NNE

I generally agree with this.

[mitchnick]

you might want to read this article

http://www.atmos-che...-11679-2011.pdf

probably, the worst of its finding are found on page 1 "We find at high latitudes that individually the solar and QBO signals are weak but that the compound solar*QBO temporal index shows a significant signal. This is such that combinations of low solar activity with westerly QBO and high solar activity with easterly QBO are both associated with a strengthening in the polar modes; while the opposite combinations coincide with a weakening."------------------> we've got scenario B so far this year. We need the sun to "cool it" fast because the QBO is doing nothing but going further negative.

[Alpha5]

you might want to read this article

http://www.atmos-che...-11679-2011.pdf

probably, the worst of its finding are found on page 1 "We find at high latitudes that individually the solar and QBO signals are weak but that the compound solar*QBO temporal index shows a significant signal. This is such that combinations of low solar activity with westerly QBO and high solar activity with easterly QBO are both associated with a strengthening in the polar modes; while the opposite combinations coincide with a weakening."------------------> we've got scenario B so far this year. We need the sun to "cool it" fast because the QBO is doing nothing but going further negative.

If you look at the first post, it seems that solar activity is on the decline.

Good read though

[Isotherm]

Thanks for the kind words everyone! Just getting a chance to read through the replies now.

John - good post as well. I generally agree with what you've said and a couple others regarding the full pattern change unlikely to occur much before January 1st. The Nina pattern looks pretty locked in for the next 1-2 weeks, but I believe it's only a matter of time before the weakening solar card begins influencing NAO/AO modality. We're already seeing that w/ some stratospheric warming showing up.

Tom, great post. In thorough agreement especially through the first two weeks of your forecast to around the Christmas Holiday. The gradient pattern has been well advertised in this range on most global ensemble suites through the last week or so of the month. I do think that there is the potential to sneak something in (likely something small and/or invovling some snow before a changeover) if we can establish some of the cold air from the higher latitudes. The ensemble guidance has been showing some poorly timed intrusions of arctic air--but in such an active pattern with energy streaming Northeast from the Southwestern United States, you never know exactly when you might get a weak to moderate perturbation to force some precipitation underneath the dome of cold air.

Moving forward--I think we are finally starting to see some of the changes that we have been looking for towards the end of the month. The CPC 05hPa temperature map has shown a weak spike over the past week or so. It's not anything wildly encouraging, but we are still running well below the mean so it is a good sign to see some warming here. I included the graphic below. Note that right around this time is usually when we start to see changes to the temperature.

The ECMWF has also recently begun to show some cracks in the armor in regards to movement and change of the stratospheric vortex. We're looking at +240hr forecast here--so a bit of caution is definitely prudent, but the changes definitely need to be noted through the end of the period.

Initial: http://wekuw.met.fu-.../ecmwf70a12.gif

The MJO looks to be unfavorable on most global ensemble guidance through around the beginning of January -- but I've begun to lose some faith in ensemble forecasting for the MJO impulses over the past several weeks. They have been highly innacurate and don't offer much of a good look into where things are going. We recently had a moderate impulse a few weeks ago which brought us through Phase 5. The forecast models are still trying to weaken the MJO into the COD and then loop back towards Phases 4-5-6 as we go into the New Year. Such a turn of events would be somewhat unfavorable -- but with the changes to the stratospheric vortex at least allowing some room for high latitude blocking -- we would definitely be better off at that point than we are now.

[Isotherm]

Note current temp at the 50 hpa level

240 hrs from now:

Note displacement of lowest temps into Asia, and sig warming across AK and Canada. The warming is more dramatic in the 100-50 hpa levels.

Up to 30 hpa, we note big changes as well.

Now:

240 hrs:

Canada, AK warming drastically, as well as Greenland.

[Isotherm]

10 hpa, starting point:

240 hrs:

Significant warming speading into Siberia, AK, western Canada, and lowest temps propagating over into Europe/Asia.

[Kaner587]

10 hpa, starting point:

240 hrs:

Significant warming speading into Siberia, AK, western Canada, and lowest temps propagating over into Europe/Asia.

pretty impressive warming depicted. Hopefully it comes to fruition.

[Hailstorm]

Many meteorologists in the main forum, except CoastalWx, are denying a significant warming event for the next 10 days and beyond. Wes (usedtobe) is saying that the warming at the 10 mb level is almost non-existent. Wxmx, meanwhile, says that this warming is likely due to an Asian Mountain Torque.

Isotherm, do you agree with their thoughts?

[Absolute Humidity]

Excellent write up as always. I do believe too that we ought see a pattern change at least begin around jan 1st. As for the current pattern, there seems to be some long term Nina lag occuring from last years moderate Nina as same held true during Dec, Jan of last year when we were experience the 2009/2010 Niño like - NAO/AO conditions during its moderate Nina. Also last year as you mentioned we had the favorable low solar activity. Not so much this past fall with arora's being seen as far south as Geogra. I suspected those were the kiss of death to the early forecasts of early mid Dec blocking, but unlike last year, the QBO is more favorable. Can this enhance any SWE and resultant blocking? Along with the last month or so of a return to less solar activity, shouldn't the QBO and low solar compensate for any lack of SWE should one not occur? Correct me if I'm wrong, thanks.

[Isotherm]

Excellent write up as always. I do believe too that we ought see a pattern change at least begin around jan 1st. As for the current pattern, there seems to be some long term Nina lag occuring from last years moderate Nina as same held true during Dec, Jan of last year when we were experience the 2009/2010 Niño like - NAO/AO conditions during its moderate Nina. Also last year as you mentioned we had the favorable low solar activity. Not so much this past fall with arora's being seen as far south as Geogra. I suspected those were the kiss of death to the early forecasts of early mid Dec blocking, but unlike last year, the QBO is more favorable. Can this enhance any SWE and resultant blocking? Along with the last month or so of a return to less solar activity, shouldn't the QBO and low solar compensate for any lack of SWE should one not occur? Correct me if I'm wrong, thanks.

Yes, it should, at least in my opinion, a major stratospheric warming event will not be necessary to destroy the current raging +NAO/AO. QBO values are slightly negative right now, and slowly falling, much more favorable than last year at this time. The QBO in conjunction with decreased geomag and solar flux should lead to the development of blocking without a SSW event.

[Isotherm]

Many meteorologists in the main forum, except CoastalWx, are denying a significant warming event for the next 10 days and beyond. Wes (usedtobe) is saying that the warming at the 10 mb level is almost non-existent. Wxmx, meanwhile, says that this warming is likely due to an Asian Mountain Torque.

Isotherm, do you agree with their thoughts?

I agree w/ the idea that the next week to 10 days will stay pretty cold up there, but definite warming occurs by week 2. Maybe Wes is looking at different data, but from what I can see, even 10 hpa is warming.