December 2021

[qg_omega]

25 minutes ago, bluewave said:

A small shift in the Pacific can make a big difference in our snowfall outcomes with -NAO and -AO patterns. Jan and Feb 2010 are probably the most extreme example of this. The NEPAC vortex in Jan was too far east so NYC only got 2.1” of snow for the month. In Feb it backed off and NYC got 36.9”. Just looking at the Greenland block both months, you would have thought that Jan would have been much better for NYC snowfall.

So while the models correcting stronger on the NAO and AO block is great to see, they still have a ways to go for the Pacific to get where we want it. We need the -PNA to weaken in further runs. Since models are always a work in progress, it would be nice to see later runs come around to a more favorable Pacific. While I am always open to models getting better than they look right now, we still have the record NEPAC vortex since the fall. Hopefully, this can change in later runs.

Jan 10 only 2.1” in NYC…trough near West Coast a little too strong

Feb 2010 36.9” in NYC…the trough backs off slightly and allows the -NAO snd -AO block to do its thing

 

Great post

[SnoSki14]

Until the PNA improves we're cooked. Euro/EPS barely give us BN temps as most of the cold is out west.

[Cfa]

I just saw a mosquito.

[MJO812]

47 minutes ago, SnoSki14 said:

Until the PNA improves we're cooked. Euro/EPS barely give us BN temps as most of the cold is out west.

Weather never changes right ?

[Uniblab]

10 minutes ago, Cfa said:

I just saw a mosquito.

Saw a bunch of them in my yard. 

[bluewave]

1 hour ago, qg_omega said:

Great post

Thanks. Our most famous version of a Pacific improvement was in 10-11. We can all remember the numerous long range snowstorms that the models were showing during the first 3 weeks of December in 2010. But the hostile Pacific resulted in only a T of snow at Newark from Dec 1 to Dec 25. The improved Pacific gave Newark a record breaking 61.5” from 12-26 to 1-27. That pattern was on track to surpass what it took 95-96 to do from November to April. But the February La Niña climo caught up with the pattern and the snows shut off.

T of snow at Newark with hostile Pacific 

61.5” with the big Pacific improvement

[Eduardo]

1 hour ago, bluewave said:

A small shift in the Pacific can make a big difference in our snowfall outcomes with -NAO and -AO patterns. Jan and Feb 2010 are probably the most extreme example of this. The NEPAC vortex in Jan was too far east so NYC only got 2.1” of snow for the month. In Feb it backed off and NYC got 36.9”. Just looking at the Greenland block both months, you would have thought that Jan would have been much better for NYC snowfall.

So while the models correcting stronger on the NAO and AO block is great to see, they still have a ways to go for the Pacific to get where we want it. We need the -PNA to weaken in further runs. Since models are always a work in progress, it would be nice to see later runs come around to a more favorable Pacific. While I am always open to models getting better than they look right now, we still have the record NEPAC vortex since the fall. Hopefully, this can change in later runs.

Jan 10 only 2.1” in NYC…trough near West Coast a little too strong

Feb 2010 36.9” in NYC…the trough backs off slightly and allows the -NAO snd -AO block to do its thing

 

 

4 minutes ago, bluewave said:

Thanks. Our most famous version of a Pacific improvement was in 10-11. We can all remember the numerous long range snowstorms that the models were showing during the first 3 weeks of December in 2010. But the hostile Pacific resulted in only a T of snow at Newark from Dec 1 to Dec 25. improved Pacific gave Newark a record breaking 61.5” from 12-26 to 1-27. That pattern was on track to surpass what it took 95-96 to do from November to April. But the February La Niña climo caught up with the pattern and the snows shut off in February. 

T of snow at Newark with hostile Pacific 

61.5” with the big Pacific improvement

I wouldn't expect a 10-11 style flip in the PAC given the SST profile this year.  But 09-10 shows that, if the ATL cooperates, even the slightest bump of that western trough can put us in business.  Granted, that was a Niño, but the point remains.  Solid posts, as always!

[ecovers94]

1 hour ago, NorthShoreWx said:

34 here.  Could be proximity to the sound, or maybe we had more breeze (or both)

Someone's gone below 32 on Long Island? Not near JFK. it's stunning to me.

[donsutherland1]

Today was another sun-filled and mild day. Much of the region again basked in high temperatures that topped out in the 50s. Similar warmth is likely tomorrow.

Elsewhere, the temperature reached at least 76° at Amarillo, TX (old record: 69°, 1929, 1962, and 1977) with near record highs being reached at Houston, St. Louis, and Wichita. Tomorrow will witness an explosion of record highs in the Midwest. Des Moines could see its first ever 70° December day. Madison could also approach or reach its monthly record. At the same time, high winds will blast a large portion of the western and central U.S.

Some of that warmth will affect the region on Thursday into Friday before cooler air again returns.

No Arctic blasts appear likely for the foreseeable future. Overall, through December 20th, there will likely be only some relatively short-lived cool shots. Afterward, the AO could go negative, increasing the opportunity for colder outcomes.

In the Midwest, Chicago has yet to receive its first measurable snowfall through December 13. Only three prior years saw their first measurable snowfall on December 13 or later:

1. December 20, 2012
2. December 16, 1965
3. December 14, 2001

The base case is that the closing 10 days of December could turn cooler, though not necessarily cold. Since 1950, there have been 7 cases where the AO averaged +2.000 or above during the first week in December, as has been the case this year. The mean December 21-31 temperature in New York City was 40.2°. The median temperature was 41.5°. The coldest was 35.3° (1951) and the warmest was 44.0° (1979). In short, this historic experience would suggest that there will be no severe Arctic outbreaks in the East this month. It also suggests that New York City will likely have an average temperature of 40° or above this month.

Afterward, if the small sample of cases where the MJO moved into Phase 7 at a high amplitude (1.75 or above) during the December 10-20 period, as occurred this month, is representative, the first 10 days of January could see below to perhaps much below normal temperatures. Both the magnitude and duration of the cold is uncertain, but the potential pattern change has support on the latest EPS weekly guidance.

Following very wet July-September periods, winter (December-February) precipitation has typically been near or below normal. The most recent exception was winter 2018-19.

The ENSO Region 1+2 anomaly was -1.4°C and the Region 3.4 anomaly was -1.1°C for the week centered around December 8. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.00°C and the ENSO Region 3.4 anomaly has averaged -0.92°C. La Niña conditions will likely persist into at least late winter.

The SOI was +16.40 today.

The preliminary Arctic Oscillation (AO) figure was +1.127 today.

On December 12 the MJO was in Phase 7 at an amplitude of 2.207 (RMM). The December 11-adjusted amplitude was 2.416 (RMM).

Based on sensitivity analysis applied to the latest guidance, there is an implied 84% probability that New York City will have a warmer than normal December (1991-2020 normal). December will likely finish with a mean temperature near 42.3° (3.2° above normal).

 

[NorthShoreWx]

25 minutes ago, ecovers94 said:

Someone's gone below 32 on Long Island? Not near JFK. it's stunning to me.

Most of the stations around here more than about 2 or 3 miles from the sound were below freezing this morning.

[Nibor]

59 minutes ago, Cfa said:

I just saw a mosquito.

I killed one today. 

[rclab]

7 minutes ago, Nibor said:

I killed one today. 

Good evening Nibor. I would have but my tolerance with my youth disappeared a long time ago. As always …..

[snowman19]

2 hours ago, bluewave said:

A small shift in the Pacific can make a big difference in our snowfall outcomes with -NAO and -AO patterns. Jan and Feb 2010 are probably the most extreme example of this. The NEPAC vortex in Jan was too far east so NYC only got 2.1” of snow for the month. In Feb it backed off and NYC got 36.9”. Just looking at the Greenland block both months, you would have thought that Jan would have been much better for NYC snowfall.

So while the models correcting stronger on the NAO and AO block is great to see, they still have a ways to go for the Pacific to get where we want it. We need the -PNA to weaken in further runs. Since models are always a work in progress, it would be nice to see later runs come around to a more favorable Pacific. While I am always open to models getting better than they look right now, we still have the record NEPAC vortex since the fall. Hopefully, this can change in later runs.

Jan 10 only 2.1” in NYC…trough near West Coast a little too strong

Feb 2010 36.9” in NYC…the trough backs off slightly and allows the -NAO snd -AO block to do its thing

 

As long as there is a mega -PNA/full latitude trough in the west, we have big problems here, real big. And the La Niña just peaked at moderate intensity in early December, which some said would never, ever happen….it should have been long dead and gone back in October, that’s going nowhere fast. The weak SPV in December didn’t happen either….the SPV is very strong and we have the strongest -PDO since the 1950’s. It’s time to stop listening to the wishcasters and listen to reality. The SE ridge is going to be a real big problem too….look at those blazing SSTs along and off the east coast…..feeding back into it 

[Rjay]

1 hour ago, ecovers94 said:

Someone's gone below 32 on Long Island? Not near JFK. it's stunning to me.

 

41 minutes ago, NorthShoreWx said:

Most of the stations around here more than about 2 or 3 miles from the sound were below freezing this morning.

My low was 30 right near ISP

[brooklynwx99]

if this pattern is a big problem then I have no idea what to say at this point

[NEG NAO]

5 minutes ago, brooklynwx99 said:

if this pattern is a big problem then I have no idea what to say at this point

where are the snowstorms in this pattern coming from ????  

[brooklynwx99]

6 minutes ago, NEG NAO said:

where are the snowstorms in this pattern coming from ????  

with a block that anomalous forcing confluence in SE Canada, a shortwave crashing in from the WC would be able to amplify given sufficient blocking of the flow

it doesn't need to be super cold either since we're in peak climo, and average 850mb temps are -2 to -5 C

March 2018 also had a significant WC trough, and it actually has a lot of similaities to the upcoming pattern w/ the Aleutian ridging and stout -NAO

[qg_omega]

9 minutes ago, brooklynwx99 said:

if this pattern is a big problem then I have no idea what to say at this point

I see cutters

[MJO812]

13 minutes ago, NEG NAO said:

where are the snowstorms in this pattern coming from ????  

Redevlopers

[MJO812]

10 minutes ago, qg_omega said:

I see cutters

With that amount of blocking?

LOL

[Rjay]

13 minutes ago, brooklynwx99 said:

with a block that anomalous forcing confluence in SE Canada, a shortwave crashing in from the WC would be able to amplify given sufficient blocking of the flow

it doesn't need to be super cold either since we're in peak climo, and average 850mb temps are -2 to -5 C

March 2018 also had a significant WC trough, and it actually has a lot of similaities to the upcoming pattern w/ the Aleutian ridging and stout -NAO

 

Shorter wavelengths in March def helped, re: 2018.  

I love seeing all the high latitude blocking.   The huge trough in the west is annoying but it's still workable.  

[NEG NAO]

8 minutes ago, MJO812 said:

Redevlopers

I Agree

 

[EasternLI]

Great thread by Griteater again. Well worth a read. 

 

[EasternLI]

Maybe we're stepping into a longer term favorable -nao cycle. They do run in decadal cycles. None to be found last decade. Last year it showed up too.

[MJO812]

47 minutes ago, NEG NAO said:

I Agree

 

Miller As will be hard to come by

[NEG NAO]

10 minutes ago, MJO812 said:

Miller As will be hard to come by

Miller B's 

[RippleEffect]

still two more days for this storm to reappear but it's looking like she gone!

[jm1220]

1 hour ago, EasternLI said:

Maybe we're stepping into a longer term favorable -nao cycle. They do run in decadal cycles. None to be found last decade. Last year it showed up too.

Yep just like the PNA which seems to run in similar cycles. The 60s had much of that time with -NAO -PNA. 

[jm1220]

1 hour ago, NEG NAO said:

Miller B's 

In this pattern if it pans out we’ll hopefully get clipper type systems to track underneath us and redevelop. Essentially the definition of Miller B. Nina seasons like these aren’t known for Miller A systems. 

[Allsnow]