December 2020 General Discussions & Observations Thread

[Cfa]

Snowpack gone, except in the shadiest areas.

[NEG NAO]

3 hours ago, mikem81 said:

These look really good. Models dont seem to match these

Post the EPO images and then you may see why............

[MJO812]

21 minutes ago, NEG NAO said:

Post the EPO images and then you may see why............

Yep

Gefs has a better pattern starting early January 

[snowman19]

1 hour ago, MJO812 said:

Yep

Gefs has a better pattern starting early January 

I don’t trust the GFS or GEFS anymore. They have been abysmal man

[uncle W]

you dont get 10" storms every other week...usually its every other year...I think the first half of January will be interesting...then a big thaw the last ten days...

[LongBeachSurfFreak]

3 hours ago, Cfa said:

Snowpack gone, except in the shadiest areas.

Amazing, still have good coverage in wantagh and only a few blocks from the bay. 
 

[Allsnow]

Above normal snowfall for December. Historically it is almost a slam dunk we see another a snowstorm this winter when we get that. Our next chance is probably in early to mid January.

[bluewave]

Clash of the Titans pattern on the EPS 11-15 day mean. Firehose Pacific Jet vs one of the strongest -NAO -AO blocks that we have seen in early January. We need to get a nice retrogression of the Greenland block back toward the PNA region. A small +PNA rise can go a long way with a North Atlantic look like that. So some interesting tracking coming up in January when the individual short waves come into better focus.

 

 

 

[uncle W]

9 minutes ago, Allsnow said:

Above normal snowfall for December. Historically it is almost a slam dunk we see another a snowstorm this winter when we get that. Our next chance is probably in early to mid January.

the only year when NYC got a 10" snowfall in December and did not get another storm near 6" was 1912-13...

[Dan76]

9 minutes ago, uncle W said:

the only year when NYC got a 10" snowfall in December and did not get another storm near 6" was 1912-13...

2020 says hold my beer...

[MJO812]

The NAO freefalls on the Eps in January

[psv88]

6 hours ago, Cfa said:

Snowpack gone, except in the shadiest areas.

Wow. Full snow cover here. 

[MJO812]

50 minutes ago, Dan76 said:

2020 says hold my beer...

I didn't know winter is already over

 

[Dan76]

4 minutes ago, MJO812 said:

I didn't know winter is already over

 

Sure hope not we'll see.

[leo2000]

1 hour ago, bluewave said:

Clash of the Titans pattern on the EPS 11-15 day mean. Firehose Pacific Jet vs one of the strongest -NAO -AO blocks that we have seen in early January. We need to get a nice retrogression of the Greenland block back toward the PNA region. A small +PNA rise can go a long way with a North Atlantic look like that. So some interesting tracking coming up in January when the individual short waves come into better focus.

 

Well luckily the GEFS has been right so far this winter. It is indicating a -EPO and the positive PNA coming in the 11-15 day range. 

 

 

[donsutherland1]

A strong storm will pass to the west of the region tomorrow through tomorrow night bringing a general 1.00"-2.00" rainfall with locally higher amounts. The storm will also bring high winds with gusts of 60 mph and perhaps 70 mph along the coastline. The temperature will likely surge into the upper 50s to perhaps lower 60s before colder air returns afterward.

In the wake of that storm, the unseasonably warm air will be driven into Atlantic Canada where record high temperatures are likely Friday through perhaps Sunday. Unseasonably cold air will push into Florida. Record low temperatures are possible in some parts of the state, especially along the Gulf Coast and southern portions of the Florida Peninsula, on Friday and perhaps Saturday.

The likely continuation of Arctic blocking through at least the first week of January will provide a higher than climatological probability for above normal snowfall for the December 21-January 10 period. The AO- is particularly important for moderate or significant snowfalls in the New York City and Philadelphia areas.

For the December 15-January 15, 1950-2020 period, the following percentages of select snowstorms have occurred when the AO was negative:

New York City:
4" or more: 66%
6" or more: 80%
10" or more: 86%

Philadelphia:
4" or more: 81%
6" or more: 85%
10" or more: 100%

Further, an AO-/PNA+ pattern is especially favorable for moderate or significant snowstorms during the first half of January. For the January 1-15, 1950-2020 period, daily snowfall reached or exceeded 4" on 1.7% of days in New York City and 1.2% of days in Philadelphia. During AO-/PNA+ patterns, those respective frequencies were 2.3% and 1.7%. In short, moderate or significant snowfalls were 37% more common in New York City and 42% more common in Philadelphia during AO-/PNA+ patterns.

The January 1-10 period likely has more potential than the days leading up to January. During the earlier period, ridging will likely protrude into the northeastern United States.  

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 +14.89 today.

Today, the preliminary Arctic Oscillation (AO) figure was -1.932.

On December 22 the MJO was in Phase 6 at an amplitude of 0.900 (RMM). The December 21-adjusted amplitude was 1.104.

Based on the latest guidance, the probability of a significant stratospheric warming event near or just after the start of January has increased. The highest levels of the stratosphere will warm during the closing days of December.

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 76% probability that New York City will have a warmer than normal December. December will likely finish with a mean temperature near 38.5°.

 

[Allsnow]

1 hour ago, bluewave said:

Clash of the Titans pattern on the EPS 11-15 day mean. Firehose Pacific Jet vs one of the strongest -NAO -AO blocks that we have seen in early January. We need to get a nice retrogression of the Greenland block back toward the PNA region. A small +PNA rise can go a long way with a North Atlantic look like that. So some interesting tracking coming up in January when the individual short waves come into better focus.

 

 

 

At that range the ensembles could just be smoothing out the pac. It won’t pick up on any pac retraction. 

[LibertyBell]

2 hours ago, bluewave said:

Clash of the Titans pattern on the EPS 11-15 day mean. Firehose Pacific Jet vs one of the strongest -NAO -AO blocks that we have seen in early January. We need to get a nice retrogression of the Greenland block back toward the PNA region. A small +PNA rise can go a long way with a North Atlantic look like that. So some interesting tracking coming up in January when the individual short waves come into better focus.

 

 

 

isnt this a precursor to some of our best KU events....firehouse pac jet into a big NAO block.....pacific supplies the moisture the block supplies the cold air

[Stormlover74]

1 hour ago, psv88 said:

Wow. Full snow cover here. 

My lawn faces south and snow is mostly gone. Across the street they still have total snow cover

[LibertyBell]

4 minutes ago, Stormlover74 said:

My lawn faces south and snow is mostly gone. Across the street they still have total snow cover

thats right, snow only exists in places that dont get full sun

 

[NorthShoreWx]

Approx a 10 - 12 degree difference between the north shore and south shore tonight.  Below freezing all evening here (30 now and slightly rising) and the snowpack is fully refrozen.  Southerly wind off the water has south shore in the low 40s. Nightime thaws are the death of snowpacks (one of the main reasons NYC can't keep a snowpack), but in 24  +/- hours it won't matter as the annual Grinch storm will be raging.

The Catskills are going to take a big hit with snowmelt, rain and flooding.  It's a shame that they'll have to reset too; it was fantastic when we snowshoed the bushwhack range on the solstice on Monday:

https://photos.app.goo.gl/ZmsYCNkQKqah6hQF9

 

 

 

[MJO812]

 

[psv88]

46 minutes ago, NorthShoreWx said:

Approx a 10 - 12 degree difference between the north shore and south shore tonight.  Below freezing all evening here (30 now and slightly rising) and the snowpack is fully refrozen.  Southerly wind off the water has south shore in the low 40s. Nightime thaws are the death of snowpacks (one of the main reasons NYC can't keep a snowpack), but in 24  +/- hours it won't matter as the annual Grinch storm will be raging.

The Catskills are going to take a big hit with snowmelt, rain and flooding.  It's a shame that they'll have to reset too; it was fantastic when we snowshoed the bushwhack range on the solstice on Monday:

https://photos.app.goo.gl/ZmsYCNkQKqah6hQF9

 

 

 

29 here with a stout snowpack 

[toople]

1 hour ago, MJO812 said:

Was the NAO negative in January 2014 and January 2015?  I never knew -NAO in January was rare.  I am still learning.

 

[Stormlover74]

2 minutes ago, toople said:

 

But it doesn't guarantee snow. Jan 2010 was not snowy. Jan. 85 was bitterly cold but not a ton of snow 

[NorthShoreWx]

1 hour ago, psv88 said:

29 here with a stout snowpack 

You can see low clouds blowing rapidly across the moon from south to north even though its still calm at the surface.  However the temp is up to 32.7 (11:45PM).  It's still very frosty (cars, etc) and the snow is frozen solid, but the temperature is all up from here.  The cloud thing with a calm frosty surface is pretty cool.

[MJO812]

27 minutes ago, Stormlover74 said:

But it doesn't guarantee snow. Jan 2010 was not snowy. Jan. 85 was bitterly cold but not a ton of snow 

No but Feb 2010 was snowy in the mid Atlantic 

[justinj]

56 minutes ago, NorthShoreWx said:

You can see low clouds blowing rapidly across the moon from south to north even though its still calm at the surface.  However the temp is up to 32.7 (11:45PM).  It's still very frosty (cars, etc) and the snow is frozen solid, but the temperature is all up from here.  The cloud thing with a calm frosty surface is pretty cool.

I went from 32 in smithtown at work to 44 at home in Holbrook

[snowman19]

8 hours ago, bluewave said:

Clash of the Titans pattern on the EPS 11-15 day mean. Firehose Pacific Jet vs one of the strongest -NAO -AO blocks that we have seen in early January. We need to get a nice retrogression of the Greenland block back toward the PNA region. A small +PNA rise can go a long way with a North Atlantic look like that. So some interesting tracking coming up in January when the individual short waves come into better focus.

 

 

 

The model continue to show a strong +EPO and have backed off on sustained +PNA. Until you lose the AK troughing, you aren’t going to get durable cold into the CONUS. The +EPO is completely cutting off any cross-polar flow. You also have a +WPO. Despite the -NAO and -AO, this is not an arctic cold pattern and it may be extremely difficult to get east coast snowstorms until the PAC changes, negative AO/NAO isn’t going to cut it with a Pacific that looks like that

[bluewave]

10 hours ago, Allsnow said:

At that range the ensembles could just be smoothing out the pac. It won’t pick up on any pac retraction. 

That’s why we have to wait for the individual short waves.  We will definitely need help from the PNA with such a strong PAC Jet and +EPO. But models won’t show those fine details until we get within about a week of the actual forecast period.