December 2017 Discussions & Observations Thread

[the_other_guy]

Large temperature swings from the North into the city this morning. 47 vs 35 Hastings to Queens.

 

NYC airports have winds from 170 or 180 degrees. HPN and SWF still have SE winds. 

 

[LurkerBoy]

LR looks dry and cold leading up to Xmas. 

[Drz1111]

1 minute ago, bluewave said:

Even the day 11-15 EPS may be hinting at the beginning of the La Nina seasonal pullback. Notice how the battlezone would be right along the East Coast from late December right into the first week of the new year. 

New EPS run trough axis more west

 

Old run

 

 

That’s a snowy look for the EC though.  Nothing massive but lots of opps for advisory level snows in the SW flow at that time of year with good high-latitude blocking.

[forkyfork]

that's a snowy look if you live in northern new england 

[snowman19]

8 minutes ago, Drz1111 said:

That’s a snowy look for the EC though.  Nothing massive but lots of opps for advisory level snows in the SW flow at that time of year with good high-latitude blocking.

Yes, Fort Kent, Maine should do well with that look...

[LurkerBoy]

Is it a cold/dry-->cutter pattern, or just mixed bag every system?

[MJO812]

4 minutes ago, LurkerBoy said:

Is it a cold/dry-->cutter pattern, or just mixed bag every system?

Why are you worrying about  a pattern change 2 weeks out ?

[LurkerBoy]

14 minutes ago, Snow88 said:

Why are you worrying about  a pattern change 2 weeks out ?

Literally just asked a question. 

[swataz]

15 minutes ago, LurkerBoy said:

Literally just asked a question. 

Some of the responses by folks in here make me literally scared to ask about things, like the fact I see two major models showing a somewhat zonal flow after this cold shot when everyone was honking about cold locking in until all eternity as late as last week...

[Rjay]

11 minutes ago, swataz said:

Some of the responses by folks in here make me literally scared to ask about things, like the fact I see two major models showing a somewhat zonal flow after this cold shot when everyone was honking about cold locking in until all eternity as late as last week...

Feel free to ask questions

[qg_omega]

1 hour ago, Drz1111 said:

That’s a snowy look for the EC though.  Nothing massive but lots of opps for advisory level snows in the SW flow at that time of year with good high-latitude blocking.

There is no blocking on that map

[MJO812]

43 minutes ago, swataz said:

Some of the responses by folks in here make me literally scared to ask about things, like the fact I see two major models showing a somewhat zonal flow after this cold shot when everyone was honking about cold locking in until all eternity as late as last week...

Ask questions

[MJO812]

26 minutes ago, qg_omega said:

There is no blocking on that map

That map is awful for the east coast

[MJO812]

Possible some snow Friday with a clipper ?

[USCG RS]

Looks more like a kitchen sink precip pattern for us here. Mix of snow, sleet, freezing rain, and rain. Great low level Arctic air to the west with -EPO, but an uncooperative NAO.

When is the last time we had the NAO copperate?

[40/70 Benchmark]

2 hours ago, forkyfork said:

that's a snowy look if you live in northern new england 

Yes, that pattern stinks even here.

[40/70 Benchmark]

15 hours ago, snowman19 said:

The weeklies are now showing what Isotherm was talking about for January with the forcing shifting and the pattern going to a classic La Niña look 

 

Agree with that.

[donsutherland1]

Last night, the EPS diverged from the continuity of its recent runs. Instead of featuring a deep trough along the East Coast in late December, the EPS displaced the trough to the west, leading to ridging along the immediate East Coast. Such a pattern is consistent with the generic composite for La Niña events. So, is it time for panic? Is winter, which got off to a fairly fast start in terms of snowfall, effectively winding down?

In both cases, the answer is “No.”

The data for winters in which a December storm brought 4” or more snow to Boston, New York City, and Philadelphia, strongly suggests that such storms have indicated a snowy to very snowy winter. 6/7 (86%) of cases saw 40” or more snowfall for New York City.

So far, in terms of the first 12 days of December, all such days featured a negative AO and positive PNA. Since 1950, there were 17 La Niña events. The persistent AO- during this period also has been associated with above average snowfall for the La Niña winters.

The following La Niña winters saw two thirds or more days during the December 1-12 period with AO- figures (seasonal snowfall figures for Central Park are included):

1955-56: 33.5” seasonal snowfall
1995-96: 75.6” seasonal snowfall
2000-01: 35.0” seasonal snowfall
2005-06: 40.0” seasonal snowfall
2010-11: 61.9” seasonal snowfall

A linear regression using the percentage of days with AO- figures and PNA+ figures for the 12/1-12 period yielded the following ranges (mean figure +/- standard error) and actual outcomes:

1954-55: Estimated range: 11.4”-35.2”; Actual: 11.5”
1955-56: Estimated range: 27.3”-51.1”; Actual: 33.5”
1964-65: Estimated range: 15.2”-39.0”; Actual: 24.4”
1970-71: Estimated range: 11.1”-34.9”; Actual: 15.5”
1971-72: Estimated range: 17.0”-40.8”; Actual: 22.9”
1973-74: Estimated range: 21.7”-45.5”; Actual: 23.5”
1975-76: Estimated range: 5.8”-29.6”; Actual: 17.3”
1983-84: Estimated range: 13.8”-37.6”; Actual: 25.4”
1984-85: Estimated range: 11.1”-34.9”; Actual: 24.1”
1988-89: Estimated range: 0.0”-11.8”; Actual: 8.1”
1995-96: Estimated range: 26.8”-50.6”; Actual: 75.6” (outlier beyond the standard error)
1999-00: Estimated range: 0.5”-24.3”; Actual: 16.3”
2000-01: Estimated range: 32.1”-55.9”; Actual: 35.0”
2005-06: Estimated range: 33.0”-56.8”; Actual: 40.0”
2008-09: Estimated range: 11.1”-34.9”; Actual: 27.6”
2010-11: Estimated range: 44.8”-68.6”; Actual: 61.9”
2011-12: Estimated range: 0.0”-20.7”; Actual: 7.4”

Seasonal  snowfall for cases with a minimum estimated figure of 20.0” or more:

1955-56: 33.5”
1973-74: 23.5”
1995-96: 75.6”
2000-01: 35.0”
2005-06: 40.0”
2010-11: 61.9”

% with < 10”: 0%
% with < 20”: 0%
% with 20” or more: 100%
% with 30” or more: 83%
% with 40” or more: 50%

Seasonal  snowfall for cases with a minimum estimated < 20.0”:
1954-55: 11.5”
1964-65: 24.4”
1970-71: 15.5”
1971-72: 22.9”
1975-76: 17.3”
1983-84: 25.4”
1984-85: 24.1”
1988-89: 8.1”
1999-00: 16.3”
2008-09: 27.6”
2011-12: 7.4”

% with < 10”: 18%
% with < 20”: 55%
% with 20” or more: 45%
% with 30” or more:  0%
% with 40” or more: 0%

Estimated 2017-2018 range: 30.6”-54.4”

Caveat: Sample size issues could arise.

Overall, there are a number of indications that winter 2017-18 will likely feature above normal snowfall in the New York City region (actually much of the Mid-Atlantic area and New England).

Finally, if one looks at the long-range GEFS, one finds a cluster of ensemble members suggesting that even as the AO- is forecast to give way to an AO+ in the near-term, AO blocking will redevelop in the extended range of the forecast. That idea is consistent with the historic experience described above. It is also consistent with the prior runs of the EPS, which suggests that the 0z EPS may be an outlier for late December. It should also be noted that weekly guidance beyond two weeks has low skill. My best guess remains that winter 2017-18 will see similar cold and snowfall to that of winter 2000-01. A 2010-11-type outcome may still be on the table, but the lack of deep blocking through the medium-term may suggest that the probability of such an outcome has decreased.

All said, there’s no need to panic as a short-term relaxation of the pattern unfolds. Winter is just starting. Things appear to be on course for a snowy winter.

[SnowGoose69]

In all honestly, unless the MJO forecasts are totally off that pattern has little chance of verifying 

[CIK62]

Month to date:

[donsutherland1]

16 hours ago, snowman19 said:

The weeklies are now showing what Isotherm was talking about for January with the forcing shifting and the pattern going to a classic La Niña look 

 

Mr. Noll included 1992-93. Winter 1992-93 was a neutral ENSO winter, not a La Niña winter. Of course, if one excludes this non-La Niña winter, the composite is somewhat different from what the map shows (much less of a trough in the west and somewhat less expansive ridging in the East).

Further, January 2011 featured a trough in the means in the East and a ridge in the means in the West, almost the opposite of what the posted map is showing.

[Drz1111]

3 hours ago, qg_omega said:

There is no blocking on that map

You need blocking for a KU storm.  Not for snow->rain or light snow events.  It’s a snowy look but not a KU look.

[CIK62]

As I pointed out a few days ago, the Control Member of the EPS is wildly different from the ensemble on New Years Day, both 500mb and 850mb T's way higher that day and still is.

[LongBeachSurfFreak]

25 minutes ago, bluewave said:

Funny how all the models trended to more of a +NAO once the cold pool reappeared just south of Greenland this week. That cold pool has become a persistent feature since the summer of 2013.

 

 

 

 

 

 

Could be the much talked about ice melt cold water. Supposed to lead to a colder Western Europe

[IntenseBlizzard2014]

2 minutes ago, bluewave said:

That cold pool appeared after the record summer Greenland melt in 2012. Shortly after that, we switched to a more +NAO regime. It was quite a record -NAO run from June 2009 to March 2013.

Probably going to see more -NAOs when the low to zero solar activity is in full effect. Greenland refreezing with lesser thaws in the summer. 

[IntenseBlizzard2014]

1 hour ago, bluewave said:

One thing we know for sure about that NAO is that the swings have become much more extreme recently. It's ridiculous to go from a record low to a record high only 5 winters apart.

 

 

 

Yes. Extreme -NAOs towards 2020.

[CIK62]

Nice 30 mile wide line of rain showers approaching now.  Snow showers are upstate only.

[snywx]

Down to 34° after a high of 38°..  Snow showers moving in

[Ja643y]

Normally don't post, but wondering if anyone sees the possibility for some LI Sound enhanced snows on the north shore with the NW winds bringing Arctic air traveling over the warm water. I know it' a rare phenomenon, but seems the set-up might be right in the next few days?

[LongBeachSurfFreak]

15 minutes ago, Ja643y said:

Normally don't post, but wondering if anyone sees the possibility for some LI Sound enhanced snows on the north shore with the NW winds bringing Arctic air traveling over the warm water. I know it' a rare phenomenon, but seems the set-up might be right in the next few days?

The water is warm enough but the air really isn’t. You need true arctic air and a perfect wind setup. The fetch just isn’t long enough