bluewave

Moving into our annual solstice warm up this week. Followed by a return to cooler than normal after Christmas. The Southeast will turn out to be the coldest part of the CONUS relative to the means this month. Florida is on track for their first colder than average month since March 2018.

I guess that he only ran the model for that storm. But it’s also happening in places like Japan. https://www.washingtonpost.com/weather/2020/12/18/japan-snow-stranded-motorists/

The WAA aloft and dryslot did their thing.

I only got 4” here before the sleet arrived. So the bar is set pretty low. I will go out on a limb say that there will be a better storm than that at some point this 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.

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.

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

Areas to our north which were below 0° today may experience one of their biggest day 5-6 temperature rises for December. The records for December were set in 2013 and 2008.

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.

These are two great tweets on how the record warm SSTs to our east are providing extra moisture to snowstorms. But on the flip side, we also get bigger rain and wind storms when the intense lows track to our west. Especially with systems that can go negative tilt.

You can think of the warm storm track near Christmas as a sacrifice bunt. The ensembles are trying to use it as a means to shift the blocking from east of New England closer toward Greenland later in the month. We saw something like this with the warm storm track back around December 1st. So while the event around Christmas looks warm and wet, it could set the stage for a cold and snowy storm track as we approach and move into 2021.

There is plenty of missing climate data for some reason this month. But NYC is at +0.5 on the xmacis2 climate site. A very Niño-like temperature departure this month with warmth along the Northern Tier and cold South.

Thanks, Don. There is a long history of people making out of place responses to things that people didn’t actually say in their original post. BGM and ALY mention possible runoff issues in their AFD. People have to realize that we are having a long range model discussion. Obviously, the actual details that show up closer in will be the ones of most relevance. So to say that x model shows y solution a week out is not a 100% endorsement of what its showing. Just to begin to think about what types of impacts could arise if such solution was actually to verify. We have the existing significant snowpack to consider, and the implications for additional runoff. Milder temperatures and some rain will arrive for Thursday into early Friday. Deepending on how much rainfall and snowmelt occurs, there could be a response on area rivers and streams, although it is still too early to tell how much of an impact this will be.

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

I was posting cold model runs last week for this week when the models latched onto the big block over the North Pole. But the coastal sections had to deal with WAA around 850mb which I pointed out that lead to the sleet and the cement snowpack. You have to take the weather as it comes. What good would it be to only show the weather you like and ignore the kinds that you don’t. All different types of weather have an impact. There are many posters on this forum that are interested in a wide variety of weather. Imagine turning on you local weather forecast and they only showed a preferred type of weather and ignored all the rest.

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.

If the guidance is anywhere close, this could be the 10th solstice warm up in a row with 55°+ temperatures. 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

The storm around Christmas may turn into another wave breaker event like near the start of December. Notice the extreme block the models are moving to following the storm east of Newfoundland. That is very similar to what happened back in early December. This early December block east of the Maritimes came before the blocking built into the Arctic like we just saw. So maybe the Christmas storm will set the table for another -AO drop into January followed by the next major snowstorm potential.

Record warmth to some type of snowfall record is becoming more frequent in recent years. November 2020 was the warmest on record in NYC at 53.0°...5th earliest seasonal 10.0”+ snowfall of 10.5” in December January to March 2020 was the 2nd warmest on record in NYC at 42.4°...trace of snow on May 9th tied with 1977 for latest on record after 7th coldest winter at 28.3° February 2018 was the warmest on record around the area with a first 80° at Newark .....NYC warmest February at 42.0°....ISP snowiest March at 31.9” of snow December 2015 was warmest on record with a +13.3...50.3° in December....greatest snowstorm on record in NYC during January of 27.5” January 2006 was the 4th warmest in NYC at 40.9° followed by the 2nd biggest snowstorm in February of 26.9”

The previous record wasn’t even 4 years old yet. The warming background state, increased moisture, and strong blocking pattern seem to be the underlying causes. Notice how warm the months before these two record storms were. Local warmth Time Series Summary for Binghamton Area, NY (ThreadEx) - Month of Nov Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 1975 44.6 0 2 2011 44.4 0 3 2001 44.3 0 4 2015 44.1 0 5 2006 43.0 0 6 1964 42.9 0 7 2020 42.8 0 - 2009 42.8 0 Time Series Summary for Binghamton Area, NY (ThreadEx) - Month of Feb Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 1984 33.1 0 2 2017 31.5 0 CONUS warmth November 2020 The average November temperature across the contiguous U.S. was 46.4 degrees F (4.7 degrees above average), which placed the month at the fourth-hottest Novemberin the 126-year record. The February 2017 temperature was 41.2°F, 7.3°F above the 20th century average. This ranked as the second warmest February in the 123-year period of record. Only February 1954 was warmer for the nation at 41.4°F. Most locations across the contiguous U.S.were warmer than average during February.Feb 28, 2017 RECORD EVENT REPORT...UPDATED NATIONAL WEATHER SERVICE BINGHAMTON, NY 1215 PM EST THU DEC 17 2020 ...SNOWFALL RECORDS SET AT BINGHAMTON NY... THE 2 DAY SNOWFALL AS OF 1015 AM IS 39.9" AT THE GREATER BINGHAMTON AIRPORT IN THE TOWN OF MAINE, NY. THIS BREAKS THE ALL TIME RECORD FOR 2 DAY SNOWFALL. THE OLD RECORD WAS 35.3" SET MARCH 14 TO 15, 2017. THE ONE DAY SNOWFALL FROM TODAY IS 26.3" AS OF 1015 AM. THIS IS THE SECOND GREATEST SNOWFALL FOR ANY CALENDAR DAY. THE GREATEST ONE DAY SNOWFALL IS 31.2" ON MARCH 14TH, 2017. ...SNOW DEPTH RECORD SET AT BINGHAMTON NY... THE SNOW DEPTH THIS MORNING AT 7 AM WAS 39 INCHES. THE OLD RECORD WAS 35 INCHES ON MARCH 15 1993 AFTER A BLIZZARD. RECORDS HERE AT THE GREATER BINGHAMTON AIRPORT GO BACK TO 1951.

The big blocking high that quickly developed over the Arctic in the 6-10 day forecast period closed the deal. But the EPS did a good job forecasting the overall pattern. One of the better EPS performances from late November into December.

Updated for Dec 16-17,2020 https://nwschat.weather.gov/p.php?pid=202012171928-KOKX-NOUS41-PNSOKX 1 S EAST TREMONT 12.4 IN 0145 PM 12/17 TRAINED SPOTTER

The model they are developing to replace the NAM missed the change to sleet that the NAM had around 8pm. So it will need more work in the future to be able to capture strong WAA around the 850mb level. https://www.emc.ncep.noaa.gov/mmb/bblake/fv3/

While we have surpassed many previous snowfall records since 1994, that winter really stands as the last widespread severe ice storm. I had an ice storm in Long Beach on Valentine’s Day 2007 and Feb 2, 2011. But neither one of those were on par with Jan 1994. Jan 94 was my only ice storm in Long Beach lasting over 12 hours. It was remarkable how even Long Beach was able to stay in the 20s with freezing rain from the early morning into the night.

This looks like the 5th earliest 10” snowstorm for NYC. #1 Nov 26-27, 1898....10.0”. #2 Dec 5-7.......2003....14.0” #3 Dec11-12...1960.....15.2” #4 Dec 15th.....1916.....12.7” #5 Dec 16-17....2020.....10.0”