December 2020 General Discussions & Observations Thread

[NEG NAO]

3 minutes ago, MJO812 said:

12z gfs para still has the early January threat 

All by its lonesome and too warm and more then likely wrong in some way...........

[MJO812]

First half of January is over

 

The PV is taking a beaten right now.  Hopefully the 2nd half is better. 

[donsutherland1]

3 hours ago, NEG NAO said:

and the SSW event in January 1973 did NOT lead to any significant increase in snowfall the rest of the winter as 72-73 ended up with 2.8 inches in NYC

That was a vortex-splitting event. Those typically favor Eurasia.

[NEG NAO]

4 minutes ago, donsutherland1 said:

That was a vortex-splitting event. Those typically favor Eurasia.

This article states that this is going to be a strong SSW event similar to 84/85 - others have said there is a chance the vortex will split - strong and split what might happen then ?

*Stratosphere warming watch* Strong signals now emerge for a disruptive stratospheric warming event in early January, possibly impacting the course of Winter (severe-weather.eu)

[the_other_guy]

29 minutes ago, MJO812 said:

First half of January is over

 

The PV is taking a beaten right now.  Hopefully the 2nd half is better. 

Can we stop doing this? Please.

 

For the record, you are probably right. But we really cant say this with any certainty.

[NJwx85]

30 minutes ago, MJO812 said:

First half of January is over

 

The PV is taking a beaten right now.  Hopefully the 2nd half is better. 

Only about 6 or 7 weeks left for prime snow season at the coast once you get passed the first third of January. Not that it cannot snow after Presidents Day but the odds start declining dramatically. After the first ten days of March it's pretty much over. Of course some of our recent March's have been excellent snow producers but that's an anomaly. 

[donsutherland1]

17 minutes ago, NEG NAO said:

This article states that this is going to be a strong SSW event similar to 84/85 - others have said there is a chance the vortex will split - strong and split what might happen then ?

*Stratosphere warming watch* Strong signals now emerge for a disruptive stratospheric warming event in early January, possibly impacting the course of Winter (severe-weather.eu)

It looks like a fairly strong event with the mean zonal winds reversing at 1 mb and 10 mb. It’s still uncertain about 30 mb. We’d have to see how the split occurs to have a better idea of its impact. Most, but not all, such cases favor Eurasia 

[SnoSki14]

47 minutes ago, MJO812 said:

First half of January is over

 

The PV is taking a beaten right now.  Hopefully the 2nd half is better. 

Way too early for that. That's a stout block on the ensembles so there's always a chance for something to sneak in. 

GEFS didn't look too bad. Even a brief relaxation of pacific jet would go a long ways. 

[donsutherland1]

Under bright sunshine, the temperature rose into the middle 30s by early afternoon. Some pictures from around Manursing Lake in Rye, NY:

[CIK62]

What a way to run a January.      Is this the result of a failed (for us) SSWE,  or just a heatwave before winter gets going?

Last January was +10.3 after the first 12 days and ended up as +6.5 for reference.

[MJO812]

48 minutes ago, CIK62 said:

What a way to run a January.      Is this the result of a failed (for us) SSWE,  or just a heatwave before winter gets going?

Last January was +10.3 after the first 12 days and ended up as +6.5 for reference.

Most likely the heatwave before winter comes roaring  back

[eduggs]

The brutal stretch continues with virtually no trackable wintry threats for the foreseeable future. It's been almost 2 weeks of unfavorable model runs across the full suite since a few days before the December 17 event. Hopefully the wait will make it sweeter when the snow tracking resumes.

[donsutherland1]

After a cold start, temperatures moderated this afternoon. Temperatures generally peaked in the middle and upper 30s across the region.

Meanwhile, on account of the strong storm that impacted the region on December 24 into December 25, more record warmth occurred in parts of Canada. That storm also brought blizzard conditions to parts of Nunavut today while eastern portions of that Province experienced unseasonable warmth.

Daily record high temperatures included:

Badger, NL: 51° (old record: 42°, 2001)
Churchill Falls, NL: 36° (old record: 22°, 2011)
Corner Brook, NL: 52° (old record: 41°, 2010)
Hopedale, NL: 42° (old record: 36°, 1976)
Pangnirtung, NU (66.15°N, 65.71°W): 39° (old record: 26°, 2000)
St. John's, NL: 50°/10.0°C (old record: 50°F/9.8°C, 1977)

Tomorrow will be partly sunny and noticeably milder before cooler air returns to the region.

The likely continuation of Arctic blocking through at least the first 10 days of January would typically provide a higher than climatological probability for above normal snowfall. Ideally, an expansive block would be anchored across the Baffin Bay or Greenland, not south of the Davis Strait.

There is growing ensemble support for the latter outcome. The probability that the block will be anchored near Newfoundland and Labrador in the extended range can inhibit opportunities for snowfall. This can especially be the case should the block attempt to link up to the western Atlantic ridge. In coming days, it will become clearer whether the recent and still ongoing shift in the ensemble guidance toward that outcome will become the most likely scenario for the first half of January.

Under this scenario, the first 10 days of January could be much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada.

The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 16. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.57°C and the ENSO Region 3.4 anomaly has averaged -1.17°C. La Niña conditions will likely prevail at least through the winter.

The SOI was +15.15 today.

Today, the preliminary Arctic Oscillation (AO) figure was -1.954.

On December 26 the MJO was in Phase 2 at an amplitude of 0.165 (RMM). The December 25-adjusted amplitude was 0.194.

Based on the latest guidance, a significant stratospheric warming event near or just after the start of January is likely. The highest levels of the stratosphere will warm during the closing days of December. The warming will begin to descend during the opening week of January. In addition, the mean zonal winds at 1 mb and 10 mb will likely reverse while the mean zonal wind at 30 mb will likely slacken considerably.

There is the proverbial fly in the ointment. It appears that this warming event could produce a split in the polar vortex. Typically, when the polar vortex splits, Eurasia is favored for cold. Displacement of the polar vortex often favors North America.

The recent snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. For now, blocking appears likely to continue into the start of January.

Based on sensitivity analysis applied to the latest guidance, there is an implied 99% probability that New York City will have a warmer than normal December. December will likely finish with a mean temperature near 39.0°.

 

[donsutherland1]

Since 1950, there were 13 cases where the EPO was +1.000 or above while the AO was -1.500 or below for at least three consecutive days during the January 1-20 period. In 3 cases, the Arctic block extended southward into the Middle Atlantic region (January 1-4, 1955; January 15-17, 1998; and, January 1-3, 2003). Below are the composite 500 mb height anomalies and temperature anomalies for that cluster:

Mean temperatures were the following:
 
Boston: 33.0°
New York City: 37.7°
Philadelphia: 40.5°
Washington, DC: 43.9°

Only Boston saw accumulating snow during the above cases. Its biggest snowfall was 3.5" during January 15-16, 1998.

The dynamical guidance is even warmer than these composite anomalies. The closest match from the above cases is the January 1-4, 1955 period.

In sum, the forecast pattern is one that will likely favor above to much above normal temperatures and little or no snowfall through at least the first 10 days of January in much or all of the Middle Atlantic Region and southern New England.

 

[Brian5671]

3 hours ago, MJO812 said:

Most likely the heatwave before winter comes roaring  back

sounds like a refrain from the last 2 years  "just wait!  2 weeks from now it will rock"

[donsutherland1]

23 minutes ago, Brian5671 said:

sounds like a refrain from the last 2 years  "just wait!  2 weeks from now it will rock"

The extended range of the EPS currently shows an evolution that could lead to a trough in the East  between January 10-15. So, unlike last winter when a stubborn EPO+/AO+ pattern locked in, things could be different this time around.

[MJO812]

0z Para for next week 

[MJO812]

Cmc now shows a storm on the 3rd

[eduggs]

Great CMC run. No deep cold, no major snow events, and complex shortwave interactions that will likely keep changing, but it's the best midrange run in a while!

[MJO812]

2 minutes ago, eduggs said:

Great CMC run. No deep cold, no major snow events, and complex shortwave interactions that will likely keep changing, but it's the best midrange run in a while!

Big battle going on with the models now with the NAO and PNA.

[eduggs]

Just now, MJO812 said:

Big battle going on with the models now with the NAO and PNA.

Yeah you could describe it that way.

But models don't know or care what the NAO or PNA are. Models just represent the physics. Climate indices are a way of simplifying and quantifying complex atmospheric states for easier human understanding.  They aren't tangible things that have causal effects on anything.

[Heisy]

All that and then the Ukie comes in completely amped haha 

[Stormlover74]

For next week's threats

 

[LibertyBell]

48 minutes ago, eduggs said:

Great CMC run. No deep cold, no major snow events, and complex shortwave interactions that will likely keep changing, but it's the best midrange run in a while!

I'm still planning on coming back to the tristate on the 3rd.  Pretty sure the weather will be fine then, it's the period between the 5th and the 10th that needs to be watched more closely.

 

[LibertyBell]

44 minutes ago, eduggs said:

Yeah you could describe it that way.

But models don't know or care what the NAO or PNA are. Models just represent the physics. Climate indices are a way of simplifying and quantifying complex atmospheric states for easier human understanding.  They aren't tangible things that have causal effects on anything.

Models represent our incomplete knowledge.  Meteorological models might be the least accurate models in all the sciences.  I can sit here and tell you about all the eclipses that will happen from now to a 1000 years from now but weather models are highly inaccurate beyond 3 days or so.  It represents the state of the science right now.

 

[LibertyBell]

2 hours ago, donsutherland1 said:

The extended range of the EPS currently shows an evolution that could lead to a trough in the East  between January 10-15. So, unlike last winter when a stubborn EPO+/AO+ pattern locked in, things could be different this time around.

it's actually better for us if it happens later.  I was thinking 5-10 but you're saying 10-15 is more likely?  Don what do you think of this "threat" on the 3rd?  I think it's a bit too soon, the models sometimes jump on something too quickly.

 

[LibertyBell]

7 hours ago, CIK62 said:

What a way to run a January.      Is this the result of a failed (for us) SSWE,  or just a heatwave before winter gets going?

Last January was +10.3 after the first 12 days and ended up as +6.5 for reference.

No it's the result of having a different climate lol.  If you look back decade by decade, average temps keep increasing.  January was one of the few holdouts, until now.  

[LibertyBell]

10 hours ago, NEG NAO said:

This article states that this is going to be a strong SSW event similar to 84/85 - others have said there is a chance the vortex will split - strong and split what might happen then ?

*Stratosphere warming watch* Strong signals now emerge for a disruptive stratospheric warming event in early January, possibly impacting the course of Winter (severe-weather.eu)

1984-85 was actually a mild winter, with a period of extreme cold in January.  That was cold and dry by the way, and not really what you want.  80s Januarys were typically very cold and dry.

 

[LibertyBell]

12 hours ago, uncle W said:

it did get colder in Feb...it remains to be seen what and if a SSW event does to our sensible weather...

Wasnt that winter very similar to 2001-02 in that we had very little snow here in both, but the south got dumped on?  I remember 2002 had a big snowstorm in the Carolinas and I think something similar happened in 1973?

[LibertyBell]

14 hours ago, bluewave said:

Pretty consistent pattern with the North American snow cover since October. Notice the big drops following the spikes back in October and mid-December. This tells us that it’s been a struggle to maintain the cold for more than brief periods. 
 

it's happening in the upper midwest too, they've had spring type flooding in Minesota.