Winter 2011-2012 Kickoff Thread | December 2011

[earthlight]

Here's the first "official" discussion thread of the winter, for all talking points and discussions related to the pattern (short/medium/long term) through the first few weeks of December. Remember the keep the banter in the banter thread, and the more serious model/forecast discussion in here.

PS- I know some of you have seen this below post already, but it definitely is the best way to kick off this thread. Let's get talking dudes.

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Snow lovers and winter weather loves have longed to hear it: It's that time of year again. December 1st marks the first day of meteorological winter in the United States, a day which is recognized only throughout the meteorological community and not on the actual calendar. However, if you think back to winter storms of the past (especially the past several years), you may find that the meteorological calendar can often be more accurate. Remember the mid-2000's when New York City recorded snowstorms in early December (December 5, 7, 9 in various years throughout the mid to late 2000's) with some significant accumulations? Those snowstorms technically fell in Autumn, according to the regular calendar. So while not proclaiming the meteorological calendar is the know all-tell all, its definitely had its moments where it more accurately depicts the season.

This year won't be one of them.

November 2011 finished as one of the warmer in recent memory, and it closed out strong in the "warm" department. Just this past week, temperatures soared to record levels two days in a row and nearly three out of four. Newark recorded 72 degree temperatures, Central Park reached 70, and all locations in the 5 boros soared into the mid to upper 60's. But the story of November wasn't just told in this last week with record temperatures, it was written well before that as the pattern became dominated by a large trough/vortex over Alaska. The lack of any high latitude blocking over Greenland or the Davis Straight (West Based -NAO by definition) only added to the problem. The Southeast Ridge flexed its muscles, and most of the Central and Eastern United States experienced above normal temperatures. Although the official numbers are not in, the ACIS monthly climate map posted above supports the dominant 500mb pattern for November (noted in a RUC analysis from November 26).

For the hard data fans, the argument begins here. There have only been a handful of November's which have followed a similar path as the one we just experienced. 2006, 2001, 1994, 1975, 1948, and 1931 come up in a list of similar Novembers temperature-wise in the New York City area. If we look back at the meteorological winters that followed those Novembers, we see some fairly startling statistics. The average snowfall in all of those winters was roughly 16 inches, which is below average. In addition only one of those listed winters featured above average snowfall , 1948, which was roughly 46 inches. None of the other winters come close to that total--so if you account for the outlier, the average snowfall is actually closer to 10 inches in winters which followed a November similar to this one. Does this mean this winter will definitely play out that way? No, but it means that we're in some pretty rare territory as far as entering winter coming off such a warm November. And previous winters which have entered this territory haven't fared too well.

Rolling forward into the first few weeks of December, the major contributors for the November warmth are going to be changing. The dynamic nature of the pattern is allowing for a fairly transient (we know, that word is becoming overused, but it does apply here) set of features over both the Pacific and Atlantic. The large vortex over Alaska (highly unfavorable for any cold air transport into the Eastern United States) is modeled to be replaced by an equally anomalous ridge. This is fairly rare---to see such a huge change within a week. 500mb height departures will have gone from near -30 to near +30 or greater. In addition, the Polar Vortex is modeled to become more established Central Canada. This means we'll finally have a source of polar and arctic air on our side of the globe (and not over Alaska with direct transport from the pole).

This will allow for more frequent penetrations of cold air from Canada as troughs pass over the Northern 1/3 of the US. However, this doesn't mean that winter weather is on the way. In fact, it means that the pattern remains disjointed. The ridge over the Pacific will allow for these cold air shots (some of them could be quite severe, mainly over the Northern Plains), but they will be rather quick. The culprit for this time period will be the lack of high latitude blocking, with the polar vortex parking over the Davis Straight. In addition, the ridge over the West Coast is modeled to retrograde some with time, meaning the favorable trough axis will remain over the Central US. In periods where the ridging over the West Coast becomes less anomalous, the Southeast Ridge will make its return and above average temperatures will follow.

The real question remains, how will the second half of December behave as far as wintry weather goes? The answer remains uncertain at this point, but it's prudent to lay out the things which we know are unlikely to happen at this time. First, we know it's unlikely that high latitude blocking will return as a major player in the pattern through at least the first three weeks of December. Most model guidance is consistent in developing a piece of the Polar Vortex over the Davis Straight and Western Greenland. This will support some shots of cold air, and the vortex may elongate and move south/southeast at times, but it will ensure that no ridging (west based -NAO) can build into these areas. The NAO may be negative for brief periods by the hard data (+1.0 to -1.0), but it should be east based and moving quickly. Second, we know that the Pacific will be generally in limbo. This doesn't mean the pattern won't be able to sustain itself for a few days, but essentially there isn't much support for the large +PNA ridge to stay fixated for all of December.

Using the MJO can be very useful as we roll forward in forecasting a few weeks in advance. In this case, forecast models and their ensembles have been extremely inconsistent in forecasting the strength and phase of the MJO over the last several weeks. However, a more significant MJO impulse has emerged over the last several days, and the forecast ensembles have adjusted accordingly. This is supported in the latest MJO phase diagram . Using the ECMWF plumes (with higher resolution and more members than the GFS), we can see the mean MJO forecast takes us through a moderate impulse in Phase 3-4 and then to a weaker Phase 5...followed by a much weaker impulse by Mid-December. The phase diagram supports a turn away from the more favorable phases 7 and 8 (for winter weather), and a weaker and less impactful mjo impulse by that time. This is not to say that the pattern can't become more favorable by then, but if current forecasts are correct..we won't have much help from the MJO at that time as it will be too weak. Note that this MJO forecast only runs through December 14th, still leaving half of the month unforecast.

Using these MJO phases, we can analyze a historical dataset of surface temperature anomalies for each phase. These charts allow us to analyze how each phase has affected the surface temperature compared to average, historically. Looking back at the phase diagram forecast above once again, we can see that much of December (through the 14th) is spent in Phases 3, 4 and 5. Not surprisingly, the surface temperature anomalies historically match up to the forecast pattern over the next two to three weeks. Additionally, looking back to Phases 2 and 3 (where we have spent the last few weeks) we can see that they match up very well with what was observed in November throughout the country. Pictured below are the surface temperature anomalies discussed above, for each phase of the MJO historically during the months of November, December, and January.

The main storm mode, aside from any potential cutoff lows (which could, admittedly, throw a large wrench into this forecast), looks to fall under the category of "Southwest Flow Event". These events feature shortwaves moving west to east, or southwest to northeast from the Central to Eastern US. The term "Southwest Flow" comes from the southwest flow of air which establishes itself in the mid and sometimes lower levels of the atmosphere during these events. These events tend to be most common in the pattern being advertised on the latest models, where some troughiness is modeled in the Southwest United States, and the Southeast Ridge is not completely dead. In this case, the Southeast Ridge combined with the forecast Polar Vortex over Eastern Canada, as well as the troughiness over the Southwest US could allow for a gradient to develop over the Mid-Atlantic and Northeast...potentially as far north as our area. This would serve as a favorable setup for the development of low pressures to our west and northwest--eventually redeveloping to our east-- as shortwaves eject northeast from the Southwest US. Although the cold air to our north (noted with the vortex over Greenland/Davis Straight) wouldn't typically allow for complete torch/heavy rain...the presence of the southeast ridge essentially assures us that the potential for moderate or greater winter weather impacts from these systems would be confined to New England.

Using all of this information, it appears that through December 15th-20th, a sustained winter pattern (with cold air and chances for snow) will not establish itself over the Eastern United States, with the potential exception of Northern New England, and the potential inclusion of Southern New England if any events are timed well with cold air intrusions. During this time period, temperatures could run generally a degree or two above seasonal averages. What happens after mid-December is what will decide how December plays out in the history books--and much of that will be decided by the eventual path of the MJO as well as solar activity. In order to see the pattern revert to a more favorable one for significant cold and snow, we will need changes in both the Atlantic and Pacific. Forecast models are still well out of their useful range towards the end of December--but rolling the MJO forward, we can assume that an eventual weakening of the vortex over Greenland will occur. What happens thereafter will depend on the MJO impulse and other effects on the Pacific--if we lose cooperation from the Pacific again, it will be another case of wash-rinse repeat.

So this year, we can say with a good amount of confidence that meteorological winter will not mark the beginning of snowy and wintry conditions as they sometimes have in the past. That being said, this isn't meant to insinuate that winter is doomed.In this case, for the snow lovers, it will take continued patience as we try and flush out an unfavorable pattern over the next few weeks. When exactly will the pattern change? We don't have an answer at the moment. These things are a gradual process. Sometimes they can suddenly jump to be more favorable, and sometimes they can take several weeks. Other times, they don't happen at all. The atmosphere can be incredibly stubborn. The state of the QBO suggests that we should not be locked in this pattern for the entire winter--and that eventually we should see the return of some high latitude blocking. The great thing about meteorology and weather forecast is that things change each day, moment even, as the atmosphere remains in motion. What we can say for sure is that winter is here for the meteorological community. Forecasting its physical arrival, in the form of bitter cold air and snowflakes flying, will be a challenge for us all over the next few weeks. I' m looking forward to it and I know mostly everybody else is as well.

[donsutherland1]

Great discussion.

[pazzo83]

Great stuff man

[earthlight]

Great discussion.

Don, thanks for the kind words. I think most on the forum are in pretty fair agreement in regards to how December will play out.

Over the next few weeks, I think we will hit a "turning point" of sorts, where we get a good look at how the winter will play out for its first half.

It will be interesting to see how (and if) the high latitude blocking responds, and if the Pacific can become better established. The cold stratosphere is helping to change anything right now.

[earthlight]

Great stuff man

Thanks bud! I'm really stoked that its the first day of meteorological winter, but it almost doesn't totally feel like it.

Everybody here seems pretty bummed out right now. Patience...we will get through it. Storms will come. Snow will fall. Weenies will fly. Fun will be had by all.

[psv88]

**** it, lets still give our OBS as if its a big storm.

47/21, clear sky. Wind NNW at 9.

I can sense the darkness will soon be propating West from Eastern Long island, its crazy they always seem to be the favored spots for darkness before it moves West...ha, beat that Earthlight!

[pazzo83]

Thanks bud! I'm really stoked that its the first day of meteorological winter, but it almost doesn't totally feel like it.

Everybody here seems pretty bummed out right now. Patience...we will get through it. Storms will come. Snow will fall. Weenies will fly. Fun will be had by all.

Yep if it's not going to be snowing, might as well be nice out.

[Chris L]

A hell of a post, John. The Nina is showing its teeth with no decent Atlantic.

[Isotherm]

Don, thanks for the kind words. I think most on the forum are in pretty fair agreement in regards to how December will play out.

Over the next few weeks, I think we will hit a "turning point" of sorts, where we get a good look at how the winter will play out for its first half.

It will be interesting to see how (and if) the high latitude blocking responds, and if the Pacific can become better established. The cold stratosphere is helping to change anything right now.

Yeah agree, usually by the 3rd week or so of December, we can get a pretty good feel as to the evolution of the rest of winter, for the most part. If we're going into Christmas or especially New Years with a very cold stratosphere and zero sign of high latitude blocking, we may have to go ahead and think spring.

[NYCSuburbs]

Funny how we started last December with tons of cold but no snow, and this year we're starting December with 60s for early next week... There's definitely some variations in the pattern as we're seeing with the -EPO for the early month and increased cold in the central US, but the pattern regarding the lack of blocking and a persistent SE ridge has been pretty much locked in place since early November and shows no signs of backing down. Most of December undoubtedly looks ugly for snow chances, but as others have said, the end of December should be helpful in figuring out what the rest of the winter will bring. Any pattern change could perhaps take place quickly though; I may be exaggerating a little here, but it's not 100% impossible that we go from an ugly December through early January to a -NAO developing and a more cold/snowy late January to February type of pattern. The first half of the winter will likely end up warmer/less snowy than average, and although I highly doubt we see anything like last winter again, perhaps the second half of the winter going into February could bring more snow events, especially focusing on New England but including NYC as well, bringing the total snow towards the average.

[supermeh]

Last year most people were alluding to the Great Pattern in December (snow and cold chances) changing for the worse in early January for the rest of Winter. The Great Pattern lasted another 3 weeks or so and eventually changed towards the end of January. Jump to this year and most thought the Awful Pattern would switch at the beginning of December. Maybe it is similar this way but in reverse order. I'm thinking we have another 3 weeks or so of this Awful Pattern and it will start showing signs of improvement by the beginning of January. I remember last year the models showing signs of the Pattern breaking towards the end of the run, ultimately not verifying. Eventually it did switch, but it takes time.

[KEITH L.I]

What a change from 12z on the GFS..lol..what happened to that big SE ridge..model is a joke

[earthlight]

What a change from 12z on the GFS..lol..what happened to that big SE ridge..model is a joke

It becomes very important to utilize the ensembles and the means in this type of set up. With such a degree of volatility, individual runs or operational runs will be prone to extremely different solutions as they struggle with anomalous features and changes.

[NYCSuburbs]

Last year most people were alluding to the Great Pattern in December (snow and cold chances) changing for the worse in early January for the rest of Winter. The Great Pattern lasted another 3 weeks or so and eventually changed towards the end of January. Jump to this year and most thought the Awful Pattern would switch at the beginning of December. Maybe it is similar this way but in reverse order. I'm thinking we have another 3 weeks or so of this Awful Pattern and it will start showing signs of improvement by the beginning of January. I remember last year the models showing signs of the Pattern breaking towards the end of the run, ultimately not verifying. Eventually it did switch, but it takes time.

Interesting point... last winter, most were expecting the pattern to change earlier in the winter (JB I think said the winter would end after Christmas at one point - that didn't work out too well), but the cold/snow lasted longer than expected. This year, most expected the pattern to become colder by early-mid December, but the change keeps getting delayed. The pattern most likely won't change into anything like last winter was for January/February, but it is a possibility that we may see a warm start and cold ending to winter.

[ORH_wxman]

Good write up. Pretty much agree on no blocking for December.

[SnowGoose69]

Interesting point... last winter, most were expecting the pattern to change earlier in the winter (JB I think said the winter would end after Christmas at one point - that didn't work out too well), but the cold/snow lasted longer than expected. This year, most expected the pattern to become colder by early-mid December, but the change keeps getting delayed. The pattern most likely won't change into anything like last winter was for January/February, but it is a possibility that we may see a warm start and cold ending to winter.

La Ninas typically do not end well but some have had some punches at the end, obviously 2000-2001 did, 1988-89 was pretty darn good late for many areas, unfortunately the NE was not one of them but there were some snow events in the south in February and March and we did get some snow in the area the first week of March as well. It seems more typical though for La Ninas to have a period in December or January where it gets very cold with chances for snow.

[earthlight]

A great graphic from the main thread, and I've been meaning to reference these. This stratospheric polar vortex is essentially parked near the N Pole and has no intention of shifting through Dec 10-15 at the very earliest. Without any help here (notice the generally oval shape and the cold to very cold stratospheric forecasts which Tom posted yesterday) the pattern really won't have much room to change in regards to high latitude ridging or blocking.

In about 14-20 days there is some support for changes here--and that should be our first peek into re-emergence towards a wintry pattern.

[tornadojay]

A great graphic from the main thread, and I've been meaning to reference these. This stratospheric polar vortex is essentially parked near the N Pole and has no intention of shifting through Dec 10-15 at the very earliest. Without any help here (notice the generally oval shape and the cold to very cold stratospheric forecasts which Tom posted yesterday) the pattern really won't have much room to change in regards to high latitude ridging or blocking.

In about 14-20 days there is some support for changes here--and that should be our first peek into re-emergence towards a wintry pattern.

Good point.. Lately I've been finding myself looking more at the models globally to see if I can see some significant pattern change anywhere.. The one thing I noticed in looking in areas very far north like this, was that the vortex was just not budging whatsoever.. In fact, if you animated it, you hardly saw any changes taking place... And actually, I didn't see anything tremendously significant anywhere else that led you to believe that a big pattern change was forthcoming

[Alpha5]

A great graphic from the main thread, and I've been meaning to reference these. This stratospheric polar vortex is essentially parked near the N Pole and has no intention of shifting through Dec 10-15 at the very earliest. Without any help here (notice the generally oval shape and the cold to very cold stratospheric forecasts which Tom posted yesterday) the pattern really won't have much room to change in regards to high latitude ridging or blocking.

In about 14-20 days there is some support for changes here--and that should be our first peek into re-emergence towards a wintry pattern.

Hey john do you have a link to where I can find those maps? Thanks

[earthlight]

Good point.. Lately I've been finding myself looking more at the models globally to see if I can see some significant pattern change anywhere.. The one thing I noticed in looking in areas very far north like this, was that the vortex was just not budging whatsoever.. In fact, if you animated it, you hardly saw any changes taking place... And actually, I didn't see anything tremendously significant anywhere else that led you to believe that a big pattern change was forthcoming

Yeah it's not moving right now. And that is a detriment to any high latitude ridging.

Couple that with the terrible MJO forecasts, poor EPO and AO...and you've got yourself a good possibility of 3 weeks of a trash pattern.

Alpha-- I'm on my phone but I'll grab it once I get back to my place.

[Weathergun]

New monthly Euro ensemble forecast is out. Looks like we get no help from MJO until January. Hopefully, the -NAO will return after the Dec. 15, when the MJO impluse is in or near the COD :

Might be too slow, however.This was the forecast from Nov. 15. Looks about 8-10 days too slow with the MJO pulse into phase 4:

[NJwinter23]

Nice work John can't say I have anything to disagree with really.. Many have mentioned how the current impressive MJO wave has a good chance to die in the phases predicted thanks to the strong easterly winds near/west of the dateline. Looks like its gonna hit this brick wall for sure.

La Nina is certainly getting a shot in the arm right now and you would expect that forcing to take over once this MJO loses some coherency. Nothing out of the tropics bodes well for December that is for sure.

Thankfully were getting this nice EPO ridge for now , probably as a result of the GOA low retrogression? Some impressive cold coming for a good chunk of the U.S. (mainly the central) thanks to this. Right now I would guess that ridge to flatten by the 15-20 and a more zonal la nina regime to take over for the latter part of December for a time.. Who knows where the MJO will be though.

And one thing about the strong stratospheric vortex and lack of blocking in our early winter is that we are building/bottling up a deep cold air source. Arctic outbreaks will probably be very severe (more so than last year and especially more so than 09-10) when and if the AO goes negative later on and sends the PV south.

[NYCSuburbs]

Observing the pattern throughout November and the lastest forecasts, there have definitely been changes in the pattern, but there's still no any big flip in the important areas needed for the East to see cold, such as the NAO and the cold stuck over Canada with a lack of blocking. There's a negative EPO, every surge warmth pushed into western Canada weakens instead of shifting east into a large SE ridge, and Monday/Tuesday seem to be the last of the strong SE ridge for a while (mid 60s again?). There's also more cold air dropping down into the central US, and although it's not over the eastern US, the fact that strong cold air is coming down from Canada is more encouraging than November. This cold central US/transient cold NE US pattern seems to last through about the mid month, when it seems that the next change takes place, with the NAO/AO dropping towards neutral and a rising EPO, almost like November, although the PNA isn't raging negative. It doesn't seem to look like another late November-like torch, but especially considering that the lack of blocking and the MJO as previously posted are in no hurry to change, perhaps we could see a slightly warmer pattern for the second half of December?

[Isotherm]

And one thing about the strong stratospheric vortex and lack of blocking in our early winter is that we are building/bottling up a deep cold air source. Arctic outbreaks will probably be very severe (more so than last year and especially more so than 09-10) when and if the AO goes negative later on and sends the PV south.

Very good point and one I haven't seen mentioned yet. Positive AO in the early winter promotes the build-up of extremely cold air at a time when darkness is at its peak in the nern hemisphere. If we can get the AO to go neg in January, which I think we will, then expect some very impressive shots of arctic air into the CONUS. Even in the upcoming pattern we'll see some decently cold 850's given the +AO in place. One thing about Nina's is when the cold comes, it tends to have more of a bite to it than Nino years.

[Weathergun]

Observing the pattern throughout November and the lastest forecasts, there have definitely been changes in the pattern, but there's still no any big flip in the important areas needed for the East to see cold, such as the NAO and the cold stuck over Canada with a lack of blocking. There's a negative EPO, every surge warmth pushed into western Canada weakens instead of shifting east into a large SE ridge, and Monday/Tuesday seem to be the last of the strong SE ridge for a while (mid 60s again?). There's also more cold air dropping down into the central US, and although it's not over the eastern US, the fact that strong cold air is coming down from Canada is more encouraging than November. This cold central US/transient cold NE US pattern seems to last through about the mid month, when it seems that the next change takes place, with the NAO/AO dropping towards neutral and a rising EPO, almost like November, although the PNA isn't raging negative. It doesn't seem to look like another late November-like torch, but especially considering that the lack of blocking and the MJO as previously posted are in no hurry to change, perhaps we could see a slightly warmer pattern for the second half of December?

It's possible, after one around the 15th, we might see a second warm episode closer to Christmas. If the Euro ensembles are correct in MJO looping back out of the COD, into phases 4/5 again.

[NJwinter23]

Very good point and one I haven't seen mentioned yet. Positive AO in the early winter promotes the build-up of extremely cold air at a time when darkness is at its peak in the nern hemisphere. If we can get the AO to go neg in January, which I think we will, then expect some very impressive shots of arctic air into the CONUS. Even in the upcoming pattern we'll see some decently cold 850's given the +AO in place. One thing about Nina's is when the cold comes, it tends to have more of a bite to it than Nino years.

No question about it...and we were draining the Arctic very early and often these past 2 years. I think of how ridiculous Feb 2010 was, there was literally nothing left in the tank up north on March 1st.

[Isotherm]

No question about it...and we were draining the Arctic very early and often these past 2 years. I think of how ridiculous Feb 2010 was, there was literally nothing left in the tank up north on March 1st.

Yep, much of 2009-10 winter featured moderately chilly days, nothing really too cold, as 850's were no lower than about -10c. Such extreme blocking basically prevented a build-up of arctic air in the nern latitudes. As a result, many of our storms in the latter part of the winter were wet snows and quite borderline actually. The December 19th-20th event was the coldest storm, with temps in the 20s throughout. The rest were generally 30-33F snows.

2010-11 had the Nina going for it, so colder overall, but still no real extreme arctic air.

[mulen]

I read no major volcanic activity this year for what its worth it does effect the weather usually in our favor for winter weather just a thought J.B was talking about that see ya.

[Sundog]

Only 44 at LGA with full sunshine. Major bust on temps today.

[earthlight]

Newark with a high of 46 today -- most forecasts were definitely a few degrees too high. I believe OKX had NYC at 49 though which isn't terrible.