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December 2020 General Discussions & Observations Thread


bluewave
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37 minutes ago, NEG NAO said:

Since nobody has been talking about the MJO lately here it is - mainly staying close to the COD which is a good thing in this pattern with all the other indicies mostly favorable for cold and snow in the east next few weeks

http://www.daculaweather.com/4_mjo_phase_forecast.php

Plenty of competing factors seem to be altering the typical La Niña forcing pattern for December. Notice how the VP anomalies are skewed further S and E than one would expect from a La Niña. The forcing near the DL is more of an El Niño look.

07E912DF-E176-49E2-BB58-10368018E7C8.gif.e0dcd1ca122db43ac7fd6bd4d0f01cba.gif

1C34D32E-9FC2-4874-B40F-AC280EBBD042.png.e92b5bdee6ece199691c542ec15ead9f.png

 

 

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1 hour ago, wdrag said:

Am on the cusp of a minor snow topic for 1-3" of snow NYC combined events Sunday and Tuesday.  Will review at 3P. If RGEM/GGEM NOT on board then probably, no topic. 

12Z CMC is further south then 12 Z NAM with precip but doesn't look to be all frozen so IMO this event is not thread worthy YET

gem_mslp_pcpn_frzn_us_11.png

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4 minutes ago, IrishRob17 said:

Break out the Christmas shorts. 

It’s interesting how persistent this solstice warm up has been especially since 2011. It has occurred under a wide variety of weather patterns. Some years like 2013 had a snowstorm just before the warm up like the forecast for this year. Others like 2017 went into the deep freeze right after Christmas. 2015 featured the historic +13.3 departure and the warmest day of the month was on the 24th.
 

Time Series Summary for NY CITY CENTRAL PARK, NY
Click column heading to sort ascending, click again to sort descending.
Ending Date
Highest Max Temperature Dec 18 to Dec 25
Missing Count
2019-12-25 57 0
2018-12-25 61 0
2017-12-25 55 0
2016-12-25 58 0
2015-12-25 72 0
2014-12-25 62 0
2013-12-25 71 0
2012-12-25 56 0
2011-12-25 62 0

 

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On 12/18/2020 at 11:51 AM, CPcantmeasuresnow said:

With a seasonal average of 5 inches I guess they're always in a snow drought. LOL

It's almost like saying Atlanta is in a snow drought. When is it a snow drought and when is it just your climate norm.

I still remember Mallow celebrating whenever a La Nina was forecast because he thought Seattle would be getting a ton of snow and the NE would get screwed lol.

 

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On 12/18/2020 at 1:47 PM, bluewave said:

Flood potential on the 12z Euro around Christmas. Especially for the interior areas with a 20-40” snowpack. Euro has heavy elevated convection and temperatures into the 50s in those  areas. Maybe we can slowly melt our pack each day so there isn’t a more rapid  melt like they could get north and west of the area if this solution verified.

 

D98EFCCF-B425-436C-89AF-F36A97C18682.gif.3da6b672d50a2595003ec08d598efaab.gif
9F7F0CD2-E99A-48CE-80D6-F69C0FDA057C.gif.eaeb451dd5ebd0ff28b3969659d7f618.gif

 

 

going back to la nina norms, isn't this a classic situation...la ninas and christmas rapid snowmelt and flooding lol?

 

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The December 16-17, 2020 snowstorm dumped 10.5" snow on New York City. December cases when 10" or more snow falls have generally seen 20" or more additional snowfall from January to the last snowfall. The historic data suggests that seasonal guidance notwithstanding, the New York City area now has a high probability of seeing 30" or more seasonal snowfall.

January-May Snowfall (1869-2020) following December Monthly Snowfall of 10" or More:
Jan-May1869-2020.jpg

Number of cases by DJF ENSO:
La Niña: 8
Neutral: 13
El Niño: 6
Total: 27

What could result in less snowfall:

1. Collapse of the ongoing La Niña and/or
2. The persistent AO- blocking yields to a sustained AO+ regime

 

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23 hours ago, jm1220 said:

Dec is typically when we’d get snowstorms in a Nina so this is evolving the way a Nina should. There’s been more blocking than some predicted which is great, but we have to keep that in place especially since part 2 of Nina winters are usually warm and snowless here. 

according to the other guy the la nina is ending?

 

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4 minutes ago, LibertyBell said:

going back to la nina norms, isn't this a classic situation...la ninas and christmas rapid snowmelt and flooding lol?

 

We can get rapid snowmelt under a variety ENSO conditions. The last one that made local headlines was in March 2015. But I am glad that areas near the coast will have a chance to gradually reduce the snowpack going into the late week storm. 

 

 

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1 hour ago, bluewave said:

It’s interesting how persistent this solstice warm up has been especially since 2011. It has occurred under a wide variety of weather patterns. Some years like 2013 had a snowstorm just before the warm up like the forecast for this year. Others like 2017 went into the deep freeze right after Christmas. 2015 featured the historic +13.3 departure and the warmest day of the month was on the 24th.
 

Time Series Summary for NY CITY CENTRAL PARK, NY
Click column heading to sort ascending, click again to sort descending.
Ending Date
Highest Max Temperature Dec 18 to Dec 25
Missing Count
2019-12-25 57 0
2018-12-25 61 0
2017-12-25 55 0
2016-12-25 58 0
2015-12-25 72 0
2014-12-25 62 0
2013-12-25 71 0
2012-12-25 56 0
2011-12-25 62 0

 

Chris remember Dec 1995 when we had the mid Dec snowstorm and then it got very cold after that and the snowpack persisted through both Christmas and New Years and was even around for the Jan 1996 blizzard?  We got the big melt a week or so after the big blizzard and we even had severe weather in Jan with temps in the mid and upper 60s with lots of flooding and the big Massapequa supermarket roof collapse!

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23 hours ago, Brian5671 said:

amazing they always go torch-yes it usually ends up above normal in areas, but the whole country?

in January it might be better to have above normal temps and high noreaster activity, below normal temp Jan usually means a suppressed pattern and it can still snow in Jan with above normal temps- as a matter of fact that might be preferred.

 

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22 hours ago, bluewave said:

Yeah, this was our first La Niña with a NYC 6”+ snowstorm in the week before Christmas since 1995. While patterns have changed greatly since then, maybe we could get another shot a major snow event like we did in early January 1996. It may come down to how strong the wave break is with the Christmas storm. The one on December 1st resulted in the record block east of Newfoundland. That blocking eventually shifted poleward and we got our significant snow event this week. Models are going for another big block east of Newfoundland after the Christmas storm. Beyond that time, models may not yet have a handle on how the blocking east of the Maritimes progresses. We can remember how models greatly underestimated the blocking over the North Pole this past week from the day 10-15 period. It suddenly popped up in the 7-9 day forecasts.  So we need to watch for something like that near the end of December. That could potentially set the table for another significant snow event. The animation below is an excellent example of how blocking since early December shifted poleward over time.

https://www.cpc.ncep.noaa.gov/products/intraseasonal/z500_nh_anim.shtml

for the rest of Dec though you dont foresee another big snowstorm correct?  This might be more like 1996 and we watch to Jan- which is fine by me.  The longer we wait the bigger it'll probably be.  Didn't someone say that when you have a 10"+ storm in Dec 9 put of 10 winters had another one later in the winter?

 

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21 hours ago, nycsnow said:

Gfs has an 87mph max wind gust over the rockaways... long duration 50-70mph wind event 

 

21 hours ago, MJO812 said:

Gfs has hurricane force gusts

whats the time frame for these high gusts?

Christmas eve (night)? or during the day or what and how long are they forecast to last?

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9 minutes ago, LibertyBell said:

for the rest of Dec though you dont foresee another big snowstorm correct?  This might be more like 1996 and we watch to Jan- which is fine by me.  The longer we wait the bigger it'll probably be.  Didn't someone say that when you have a 10"+ storm in Dec 9 put of 10 winters had another one later in the winter?

 

The Christmas storm looks to really create a major wave breaking event. So I am taking a wait and see approach as to how long after that we can expect a colder and snowier storm track. I am hoping that we can finally get a cold enough storm for the South Shore to finally get into the jackpot zone like we were in 15-16, 16-17, and 17-18.

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