December 2017 Discussions & Observations Thread

[CIK62]

Getting uglier in our more immediate future---next 7 days averaging a balmy 44degs. now, or 8degs. AN.

[uncle W]

4 hours ago, uncle W said:

it could be wrong...it could be downplaying a very positive ao...

 

the black obs line is riding the max red lines on the 10 and 14 day forecast...if it continues that way we should be seeing a plus 3 ao...these forecasts never went below the lowest member forecast but exceeded the highest member forecast a few times...during the Dec 83 arctic outbreak the ao was rising from a negative to almost +4.5 on the 27th...we have seen arctic outbreaks with the ao as high as +5...We never had a major snowstorm with a plus 2 sd ao...

[weatherpruf]

1 hour ago, uncle W said:

the black obs line is riding the max red lines on the 10 and 14 day forecast...if it continues that way we should be seeing a plus 3 ao...these forecasts never went below the lowest member forecast but exceeded the highest member forecast a few times...during the Dec 83 arctic outbreak the ao was rising from a negative to almost +4.5 on the 27th...we have seen arctic outbreaks with the ao as high as +5...We never had a major snowstorm with a plus 2 sd ao...

I remember Dec 83, the gas lines froze in my AMC Spirit and i had to knock on someone's door and beg to be let in to use the phone.....

[SnoSki14]

1 hour ago, CIK62 said:

Getting uglier in our more immediate future---next 7 days averaging a balmy 44degs. now, or 8degs. AN.

December may very well be AN.

[Ralph Wiggum]

December may very well be AN.

This could be one of those rare years where DJF avg AN temps and AN snowfall.

[NorthShoreWx]

8 minutes ago, Ralph Wiggum said:

12 minutes ago, SnoSki14 said:

December may very well be AN.

This could be one of those rare years where DJF avg AN temps and AN snowfall.

That has not been rare at all recently.

[Mophstymeo]

2 hours ago, redbanknjandbigbasslakepa said:

I thought this was going to be a couple day relaxation and those who were calling for the SE ridge we’re going to be wrong? Beuller? Beuller?

The irony of your saying this is completely lost on you, isn't it?

[UlsterCountySnowZ]

5 minutes ago, Mophstymeo said:

The irony of your saying this is completely lost on you, isn't it?

He's back....took his hiatus after busting badly with the other day, got embarrassed by Paul, now hes back stirring the pot again...some people never learn

[Mophstymeo]

13 minutes ago, UlsterCountySnowZ said:

He's back....took his hiatus after busting badly with the other day, got embarrassed by Paul, now hes back stirring the pot again...some people never learn

Well, maybe this is a sign the SE ridge will relax a bit and we can get our mojo back.

[redbanknjandbigbasslakepa]

3 minutes ago, Mophstymeo said:

Well, maybe this a sign the SE ridge will relax a bit and we can get our mojo back.

Where’s he on his blown calls? He mocked you all on the se ridge for Christmas but looks like he’ll be flipping burgers on the patio.

[MJO812]

Gfs has the front through by the 24th now

Colder than the 18z run

White Xmas for many on this run

[WEATHERBUFF]

It is really hard to get a below normal month these days, if we are 1 or 2 above the so-called normal temps we probably will still be cooler than recent trends for december. 1980's were much cooler than today and to some degree as were the 90's and even 2000's. Those averages have nothing to do with today's climate for we are a couple of degrees warmer than that period...just look at the recent trends.

[Paragon]

5 hours ago, NorthShoreWx said:

That has not been rare at all recently.

I was just going to say lol.  We recently had a 40/40 winter.

[CIK62]

Next 8 days averaging 42degs., or 7degs. AN.

[MJO812]

Gfs continues to trend colder with possible snow by Xmas .

[Zelocita Weather]

Yup, modeling looking excellent now from xmas eve/xmas into January...

[Ralph Wiggum]

Where’s he on his blown calls? He mocked you all on the se ridge for Christmas but looks like he’ll be flipping burgers on the patio.

New models and ens are flattening out the SER and trending earlier on doing so. Some guidance now trending snowfall Christmas Day.

[snowman19]

2 hours ago, Snow88 said:

Gfs continues to trend colder with possible snow by Xmas .

The GFS/GEFS is very likely too fast as is usual for that model. More likely the cold comes after Christmas Day like the EPS and GEPS are showing

[donsutherland1]

Following Christmas, the guidance suggests a fascinating battle of the teleconnections. The EPO remains forecast to dive to perhaps as low as -3.000. The Arctic Oscillation (AO), which now stands at a monthly high figure of a preliminary +2.047 is forecast by numerous ensemble members to be positive to possibly strongly positive before falling toward New Year’s Day. The PNA is forecast to be fairly neutral (somewhat negative to somewhat positive depending on which ensemble members one examines.

Yet, even as the AO+ can delay the onset of cold (and for that reason I continue to lean toward the ECMWF guidance that shows the cold moving into the East on or just after Christmas Day), the outcome does not always mean that the cold won’t arrive. Should the SOI remain negative, as is currently the case, the cold could be delayed further. However, the guidance currently suggests that the Pacific trade winds will begin to increase, leading to a positive SOI within the next 7-10 days.

Running a composite based on the teleconnections to avoid a possible skewed picture from a disproportionate reliance on the AO, which can have among the largest correlations to outcomes in the northeastern U.S., the following data from the 12/20-31/1981-2010 base period is available for NYC.

All dates:
Mean temperature: 36.0°

Expected pattern based on the AO, PNA, and EPO forecasts: 34.9°
…Expected pattern with an SOI-: 36.6°
…Expected pattern with an SOI+: 33.6° (presently the most likely outcome)

Based on this data, the GEFS, and a preference for the EPS for the Day 10-15 outlook, I remain confident that December has not yet seen its coldest readings in such cities as Bridgeport, New York, and Newark (lowest temperatures respectively 16°, 20°, and 17°). I also expect additional snowfall at all three locations before the month has ended. For the winter as a whole, the Middle Atlantic and southern New England regions still remain on course for above to possibly much above average snowfall.

Seasonal snowfall anomalies to date are as follows:

Baltimore: 3.8” (+2.0”)
Boston: 6.1” (+0.8”)
Bridgeport: 6.4” (+3.6”)
New York City: 7.0” (+4.7”)
Newark: 7.1” (+4.4”)
Philadelphia: 7.7” (+6.0”)
Portland: 8.9” (+1.0”)
Providence:  5.7” (No anomaly)
Washington, DC: 1.7” (+0.1”)

In terms of NYC’s monthly temperature, based on a sensitivity analysis using the latest modeled data, the City still has about a 50%-56% probability of having a cold anomaly.

Monthly Mean Temperature:
Through:
12/17 38.2°
12/20 38.4° - 39.0°
12/25 38.6° - 40.2°
12/31 35.9° - 38.4°

[Ralph Wiggum]

 
At this point the models are all in pretty good agreement. The Euro and CMC bring the Arctic front through on the 26th and the GFS 25th. Either way, the cold comes east after the December thaw this week. Matches the theme of all the competing influences to our pattern right now. -EPO/+NAO/LA Nina/MJO/WPAC forcing/Very warm water of East Coast. So this is a mash up pattern where a bunch of elements are thrown together. The final outcome will be a fusion of all the various influences into a unique December pattern.

Its weird the EPS mean has the front thru during the first part of the 25th and a closed surface slp center off the coast in the Gulf Stream with an uptick in precip during the day on the 25th. Would have been nice if we had the cold established prior as I hate cold chasing the precip. However, we did ok Dec 9 at the beginning of a pattern shift without the cold air fully established so who knows. Maybe its a trend this season.

[NEG NAO]

10 minutes ago, Ralph Wiggum said:

3 hours ago, bluewave said:

 
At this point the models are all in pretty good agreement. The Euro and CMC bring the Arctic front through on the 26th and the GFS 25th. Either way, the cold comes east after the December thaw this week. Matches the theme of all the competing influences to our pattern right now. -EPO/+NAO/LA Nina/MJO/WPAC forcing/Very warm water of East Coast. So this is a mash up pattern where a bunch of elements are thrown together. The final outcome will be a fusion of all the various influences into a unique December pattern.

Its weird the EPS mean has the front thru during the first part of the 25th and a closed surface slp center off the coast in the Gulf Stream with an uptick in precip during the day on the 25th. Would have been nice if we had the cold established prior as I hate cold chasing the precip. However, we did ok Dec 9 at the beginning of a pattern shift without the cold air fully established so who knows. Maybe its a trend this season.

The EPS was further east with the 540 line by the 25th then the Euro OP - the EPS is trending towards the more aggressive GFS - BUT you can't trust any of these solutions past 3 or 4 days this season so far especially regarding any storms that may or may not be on the horizon ...................

[AfewUniversesBelowNormal]

Usually these big Alaska cutoff blocks are more of a sign of coming massive +EPO, US blowtorch, than main pattern driver. 

[LongBeachSurfFreak]

I have said this once and I’m going to say it again. Hopefully people listen this time.

 

Claiming victory because the models support your thinking for an event or pattern more then 24 hours out needs to stop. It’s ruining legitimate discussion. 

 

An example. Claiming we are heading into the furnace. Has this occurred? No it hasn’t. So have fun flipping burgers in the snow.

[JetsPens87]

9 minutes ago, AfewUniversesBelowNormal said:

Usually these big Alaska cutoff blocks are more of a sign of coming massive +EPO, US blowtorch, than main pattern driver. 

A massively anomalous Alaskan ridge like that is most certainly a main pattern driver and will push cold air into the lower 48, just a matter of how far east it can get with the SE ridge rearing. 

 

I dont see how that extreme block signals a  coming US blowtorch.

[JetsPens87]

6 minutes ago, AfewUniversesBelowNormal said:

Temporarily, these are usually transitional and the follows out weighs it 2:1 or 3:1.

According to what?

[JetsPens87]

1 minute ago, AfewUniversesBelowNormal said:

Happens less when is led by 10mb warming... I guess it's tropical forcing or whatever, but it may not be. is just the pattern of the time. 

Don would probably be able to put it together better than myself but as far as I’m aware I know of no direct correlation between a highly anomalous -EPO being a precursor to a highly anomalous +EPO and widespread above average US temperatures.

[MJO812]

Epo and Wpo are crashing

Cold weather should be here by xmas

[AfewUniversesBelowNormal]

28 minutes ago, JetsPens87 said:

Don would probably be able to put it together better than myself but as far as I’m aware I know of no direct correlation between a highly anomalous -EPO being a precursor to a highly anomalous +EPO and widespread above average US temperatures.

It's more common in the 2000s 

[JetsPens87]

9 minutes ago, Snow88 said:

Epo and Wpo are crashing

Cold weather should be here by xmas

Still have that SE ridge that the EPO crash is going to pop to contend with 

[donsutherland1]

47 minutes ago, AfewUniversesBelowNormal said:

Usually these big Alaska cutoff blocks are more of a sign of coming massive +EPO, US blowtorch, than main pattern driver. 

I disagree.

Using the 1981-2010 base period, there were five cases where the EPO fell to or below -3.000 sigma (12/1-1/15 period). Although all cases saw the EPO reach somewhat positive values within 6-11 days after it bottomed out, it took three weeks or longer in 80% of the cases for the EPO to reach +2.000 sigma or above (60% 30 days or longer). In one case, it remained below +2.000 sigma throughout the rest of meteorological winter.

The worst outcome occurred in winter 1989-90. The best outcomes occurred during winters 2004-05 and 2009-10.

The above is a very small sample size, so some caution is in order. However, there is enough data to suggest that the development of a near-term strongly positive EPO is nowhere near a fairly certain outcome.