December warm NOT White

[PB GFI]

With such a strong POS ENSO event present many expect the higher heights across Canada to cut off any extended cross polar flow .

An above normal 2m temp regime looks to be on tap , ( +2 @ KNYC)

As we get deeper into Dec it only has to be cold enough to snow.

Here's wishing all of you a Merry Christmas and a happy holiday season .

[uncle W]

If the ao/nao are positive for December it most likely will be mild...If there is a negative period it could snow around that time...

[SnoSki14]

An impressive +AO is forecast to rise at or above 4 again in a few days. Two very high indices in one month seem fairly rare.

[LongBeachSurfFreak]

I give a 95% chance of wet not white at the coast. I think inland and elevated might be able to pull something off

[JerseyWx]

Awhile ago I said I had a feeling December would be on the warmer side. I have no science to back that up, just a gut feeling, and I could be completely wrong.

Like Long Beach said, inland areas in the mountains will almost certainly get some kind of snow, even if it's only a few inches. But besides that, I think we see a December similar to last year with above normal temps and rain.

[donsutherland1]

An impressive +AO is forecast to rise at or above 4 again in a few days. Two very high indices in one month seem fairly rare.

A late November strongly positive AO hasn't been a good outcome when one is looking for a lot of blocking for the winter. By then, the seasonal transition is nearing an end, so it becomes more difficult to perturb the strong polar vortex. Since 1950, the following years saw the AO reach +3 or above during the November 20-30 period: 1972, 1978, 1994, and 2011. 

[nzucker]

A late November strongly positive AO hasn't been a good outcome when one is looking for a lot of blocking for the winter. By then, the seasonal transition is nearing an end, so it becomes more difficult to perturb the strong polar vortex. Since 1950, the following years saw the AO reach +3 or above during the November 20-30 period: 1972, 1978, 1994, and 2011.

Interestingly, not all those winters were warm.

72-73 had a record breaking arctic outbreak in the Mountain West in December, while December had a significant ice storm in the NYC area. February had a major Southeast snowstorm.

78-79 was the coldest winter in the CONUS in modern history. No state had above average temperatures.

94-95 was a warm winter, but February was fairly cold with a major snowstorm for NYC.

11-12 was a nationwide torch, especially March.

So, conditions varied for the winter. 78-79 had very good blocking for the entire winter, especially February.

[donsutherland1]

Interestingly, not all those winters were warm.

72-73 had a record breaking arctic outbreak in the Mountain West in December, while December had a significant ice storm in the NYC area. February had a major Southeast snowstorm.

78-79 was the coldest winter in the CONUS in modern history. No state had above average temperatures.

94-95 was a warm winter, but February was fairly cold with a major snowstorm for NYC.

11-12 was a nationwide torch, especially March.

So, conditions varied for the winter. 78-79 had very good blocking for the entire winter, especially February.

Other factors also play a role. At least two of the above winters had a very warm December. Given the current El Niño, I think this latest data lends credence to the idea of a warm December. Also, so there's no confusion, I'm only focused on possible implications for December consistent with this thread. 

[uncle W]

the average snowfall for 1972-73 and 1994-95 is 7.3"...the other two were not el nino's...the coldest nine December's during an el nino had a negative ao and nao on average...but you can still get snow in a sea of warmth if the ao goes negative at some point during the month...1979 and 1982 saw that...

[uncle W]

there have been six Christmas days with the temperature reaching the 60's and 15 days with the temperature reaching 55 or higher...The worst of the worst...reds are el nino years...

year...max min rainfall

1982...64 41 0.02"

1889...64 43

1940...62 40

2014...62 44

1979...61 50 0.87"

1964...60 49 trace

1965...59 47 0.65"

1900...59 44

1932...59 47

1994...59 41

1893...58 45

2008...57 33 0.13"

1936...56 40

1915...55 38 0.01"

1933...55 34

[Damage In Tolland]

With every piece of LR guidance showing ++NAO and ++AO and +EPO..and a strong PAC jet..scouring all of the cold air out of Canada and replacing it with mild pacific air, thus erasing any snow cover that may have been gained over the southern 2/3 of the country..it's likely going to be one of the warmest Decembers the northern tier has ever seen. It would not be surprising (to me) if NYC and most of SNE goes virtually snowless in Dec. While I think the warmest anomalies are over the upper midwest, it's going to be very mild over the northeast and it also looks fairly dry.

[PB GFI]

A +NAO/+AO El Nino December has been a mild signal going back to at least 1980 for NYC.

You need a very strong -AO/-NAO to overcome the warm seasonal El Nino response 

in December like 2002 and 2009.

 

NYC December temperature departures during +NAO/+AO El Nino years since 1980:

 

1982....+7.3

1986....+2.8

1991....+3.4

1994....+5.6

2004....+1.1

2006....+6.3

2014....+3.0

Its why I always thought a plus anomaly for December was an easy call.

The warmer CFS is plus 3. I have no problem with it. I am closer to plus 2 .

[Brian5671]

I agree, if it's stormy we have a chance, although last year was very wet and we had little to no snow.   It's often a tough month for snow, we've been spoiled with some decent to historic events in December the last 15 years. Dec 02 Dec 03, Dec 06/07 (?) can't remember which one, Dec 09, Dec 10, Dec 13 all had good events that come to mind.

[Brian5671]

The good thing about a mild El Nino December is that it often proceeds the the traditional January 15th through March Back-loaded

winter pattern.

Different pattern, but that's what we got last year.  The only error was models/forecasters going for an earlier pattern change around 12/20 which was 3 to 4 weeks too early.

[PB GFI]

Different pattern, but that's what we got last year.  The only error was models/forecasters going for an earlier pattern change around 12/20 which was 3 to 4 weeks too early.

What's different ?

[PB GFI]

The good thing about a mild El Nino December is that it often preceeds the the traditional January 15th through March Back-loaded

winter pattern.

Agree Chris , the Euro which once again was so good with regards to the NINO starts to really retrograde the pattern at 500 once to Jan.

The December warmth is expected so too are the calls for winters over and the weenie bridge jumpers if this place doesn't look like Mt Snow soon

[Brian5671]

What's different ?

You trolling?   Very weak Nino last year and a top 2 or 3 event this year.  I'd say that's a bit different

[PB GFI]

You trolling? Very weak Nino last year and a top 2 or 3 event this year. I'd say that's a bit different

Your pattern is derived by the mean positions of the NEGs and POSs at 500 .

The strength of the NINO alone doesn't constitute a different pattern you bozo.

What materializes from it could be different but you have another NEG EPO establishing itself in the means , no SE ridge again this year and +AO early on. The tropical forcing is in roughly the same place and the fact that 3.4 and 4 are so warm benefit you.

Once again the warm waters on EP region are helping to set up the same NEG in the GOA like we saw last year.

The only difference is you will not see the same amount of cross polar flow as you saw last Feb , but it doesn't have to be - 8 in Feb , -2 gets the job done

So again what's different now ?

[Brian5671]

Your pattern is derived by the mean positions of the NEGs and POSs at 500 .

The strength of the NINO alone doesn't constitute a different pattern you bozo.

What materializes from it could be different but you have another NEG EPO establishing itself in the means , no SE ridge again this year and +AO early on. The tropical forcing is in roughly the same place and the fact that 3.4 and 4 are so warm benefit you.

Once again the warm waters on EP region are helping to set up the same NEG in the GOA like we saw last year.

The only difference is you will not see the same amount of cross polar flow as you saw last Feb , but it doesn't have to be - 8 in Feb , -2 gets the job done

So again what's different now ?

Fair argument there.   I think we see some bigger events this year.  Last year's Southern Jet was not all that active, this year I think the Jet is rocking so we get some Miller A's and even some big cutters that we did not see last year 2nd half.

[PB GFI]

Fair argument there. I think we see some bigger events this year. Last year's Southern Jet was not all that active, this year I think the Jet is rocking so we get some Miller A's and even some big cutters that we did not see last year 2nd half.

December will be a grind , warm starts usually test ones patience with regards to their ideas .

We saw great forecasters last year give up just before the jail break . They had the right idea all along , but bad early patterns will frustrate even the best.

This winter will not be as cold as last year ,( last Feb was a 1 in 75 year event ) but then again if we manage plus 1 while being wet it doesn't mean disaster.

So Def I'm Def not cold , I'm Just not in the suck camp.

[uncle W]

Its why I always thought a plus anomaly for December was an easy call.

The warmer CFS is plus 3. I have no problem with it. I am closer to plus 2 .

most of the coldest Decembers with various enso had a negative ao/nao...so it's not just el nino Decembers that need a negative ao/nao...

[Isotherm]

A strongly positive modality of the NAM doesn't have much relevance insofar as the rest of the winter given the ENSO base state, namely, if we had a pattern different than this, it would be atypical.

 

And again, just throwing this out there: people forget that it can snow w/ a warm monthly departure. December 1957 was +3 to +4 temperature wise, yet Newark recorded 16.2", mostly via two transient dips in the NAO/AO early and mid month. The active sub-tropical jet, which appears will eventually develop this month, provides more opportunities.

 

We likely will not see a 1957 scenario, but I wouldn't be surprised to see a moderate event at the coast in December.

[uncle W]

A strongly positive modality of the NAM doesn't have much relevance insofar as the rest of the winter given the ENSO base state, namely, if we had a pattern different than this, it would be atypical.

 

And again, just throwing this out there: people forget that it can snow w/ a warm monthly departure. December 1957 was +3 to +4 temperature wise, yet Newark recorded 16.2", mostly via two transient dips in the NAO/AO early and mid month. The active sub-tropical jet, which appears will eventually develop this month, provides more opportunities.

 

We likely will not see a 1957 scenario, but I wouldn't be surprised to see a moderate event at the coast in December.

Novrmber 1957 had a very negative ao but positive nao...The ao went positive around the time of the big snowstorm on the 3rd...

[PB GFI]

A strongly positive modality of the NAM doesn't have much relevance insofar as the rest of the winter given the ENSO base state, namely, if we had a pattern different than this, it would be atypical.

 

And again, just throwing this out there: people forget that it can snow w/ a warm monthly departure. December 1957 was +3 to +4 temperature wise, yet Newark recorded 16.2", mostly via two transient dips in the NAO/AO early and mid month. The active sub-tropical jet, which appears will eventually develop this month, provides more opportunities.

We likely will not see a 1957 scenario, but I wouldn't be surprised to see a moderate event at the coast in December.

Yeh, Tom I have posted above we just have to be cold enough to snow . I do like the plus side for Dec but it is a winter month and you can always snow between mild periods with the right set up.

I don't like early Dec snows with +NAO s, as we need that mechanism with such a warm Atlantic early on to stave off easterly winds for the coast .

[Isotherm]

Yeh, Tom I have posted above we just have to be cold enough to snow . I do like the plus side for Dec but it is a winter month and you can always snow between mild periods with the right set up.

I don't like early Dec snows with +NAO s, as we need that mechanism with such a warm Atlantic early on to stave off easterly winds for the coast .

 

 

Agree. I went warm / very warm (probably +2 to +3) and less snow than average for December in my winter outlook pattern evolution. Just throwing an alternative scenario out there, as a "what can happen." However, I expect the vast majority of our winter weather to occur after New Year's this year.

[Isotherm]

Novrmber 1957 had a very negative ao but positive nao...The ao went positive around the time of the big snowstorm on the 3rd...

 

 

There was another dip in the NAO/AO in mid December, amidst a regime of +NAO/AO overall. My point was that a +NAO/AO in the means during December should not send people to the edge of a cliff, due to the strong ENSO state.

[nzucker]

Novrmber 1957 had a very negative ao but positive nao...The ao went positive around the time of the big snowstorm on the 3rd...

57-58 was the 3rd snowiest winter in Dobbs Ferry recorded history, behind 60-61 and 95-96. Despite the warm December, the 57-58 winter featured 80" of snowfall here, with a moderate 8" storm in December. February had a major -NAO block with a 16" snowfall and below average temperatures, and March had twin snowfalls around the equinox, one totalling 18". The strong, west based -NAO block over Southern Greenland offset a mainly hostile Pacific Nino pattern that featured a strong GOA low. There wasn't much extreme cold in 57-58, as none of the area got below 0F, but it was cold enough for massive late-season snows.

I see this season as potentially a blend between 57-58, 65-66, 82-83, and 86-87. The cold west early is also reminiscent of December 1972, though I doubt the East gets that little snow, as this Nino is more west based.

[uncle W]

February 1958 was very cold the first three weeks with a blizzard mid month...It got down to 3 degrees after the storm in NYC...8-10" fell across the city...

[IntenseBlizzard2014]

February 1958 was very cold the first three weeks with a blizzard mid month...It got down to 3 degrees after the storm in NYC...8-10" fell across the city...

I remember reading about that month. There were a series of moderate to heavy snowstorms in the Tri State Area. Especially N&W of the city. Right?

[uncle W]

I remember reading about that month. There were a series of moderate to heavy snowstorms in the Tri State Area. Especially N&W of the city. Right?

the only other one I remember was a snow to rain event at the beginning of the month...There was a thaw the last week of the month with some rains...March 58 had two wet snowstorms a week apart...