bluewave

Yeah, the standing wave near Australia is classic La Niña. It acts to pump the Aleutians Ridge and cause a deep -PNA trough over the Western US. While the individual MJO composites don’t always match, this month is very close to the La Niña December forcing composite.

While no piece of guidance excels at snowfall forecasts beyond 120 hrs, the GFS has been really struggling. It has had numerous snowy forecasts beyond day 5 since late November that never verified. The upgraded Euro has been doing much better with very little snow in the forecast. So we may need the Euro and EPS on our side for a more realistic chance of snow.

That’s why getting a favorable Pacific is so important for our area.

That was one of the reasons that the original board split into regional forums. There is just too much variation between New England, our area, and DC to Philly. Some teleconnection patterns favor one area but not the others. It’s always a big win if all 3 areas can do well at the same time.

High temperatures usually beat expectations when we have a deep trough over the Western US. The longer range forecasts for Christmas underestimated the strength of the SE Ridge. But you could see the risk of SE Ridge from the strong -PNA even though the models didn’t show it 10 days ago. New run Old run

The Euro seasonal did a great job with the December and November forecast.

It’s not a matter of being impatient. We just don’t want to be in the NYC below 3” December La Niña club. Very disappointing to see things getting pushed back now into early January. The new 91-20 climate normals seasonal snowfall in NYC is 29.8”. NYC has never reached 30.0” in a La season with under 3.0” in December since 1950. This must be related to the fact that the good La Niña years for snowfall get off to an early start since they are front-loaded. NYC December snowfall during La Ninas and seasonal snowfall. 2017…..7.7….40.9 2016….3.2….30.2 2011…..0.0….7.4 2010….20.1….61.9 2008….6.0…..27.6 2007….2.9……11.9 2005….9.7……40.0 2000….13.4…..35.0 1999…….T…….16.3 1998…..2.0……12.7 1995…..11.5…..75.6 1988…..0.3……8.1 1984…..5.5…..24.1 1975…..2.3…..17.3 1974……0.1…..13.1 1973…..2.8….23.5 1971…….T……22.9 1970……2.4….15.5 1964……3.1….24.4 1955…...3.3…33.5 1954…...0.1….11.5 1949……1.5….14.0

We have built up some pretty high temperature departures on the month so far. NYC….+5.7…EWR…+7.2….LGA….+6.2….JFK…..+5.9. With the much warmer 1991-2020 climate normals, all we need is a +3 or higher to finish in the top 10 warmest Decembers. The latest ensembles have around a +2 to +3 in the means for the next 10 days.

NYC is currently in 4th place for warmest December 1st to 17th. A large part of the country is also having top 5 warmth. 7 of the top 10 warmest readings have been since the late 1990s. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Dec 1 to Dec 17 Missing Count 1 2015-12-17 52.0 0 2 2001-12-17 50.1 0 3 1998-12-17 49.8 0 4 2021-12-17 46.6 0 5 1953-12-17 45.0 0 6 2012-12-17 44.8 0 - 2011-12-17 44.8 0 7 1999-12-17 44.4 0 8 1897-12-17 44.3 0 9 1956-12-17 44.0 0 - 1879-12-17 44.0 2 10 1923-12-17 43.8

I don’t think that we are downplaying anything. The entire Northern Hemisphere land area is coming off the warmest fall on record. So it’s no surprise December has been more like a fall month than winter. This forum contains short and long range forecast discussions. So it’s natural to look forward to getting a possibly better pattern in early January.There have been no claims on how long any improved pattern could last. Let’s just wait and see what we can get in early January. Even if a better pattern compared to what we have now lasts only a few weeks, we’ll take it. Very hard to extrapolate a whole month based on an early January snapshot. Things could shift more or less favorable in the next two weeks.

Nice paper. We are on track to see one of the strongest Aleutians Ridges on record for the month of December. This is a much more exaggerated ridge than we typically see with La Ninas. Maybe the typhoon recurve, record low and wave break near Japan, and record warm WPAC SSTs contributed. Even without the MJO, the La Niña composite favors a shift of this ridge closer to the West Coast in January. It can be a much better pattern then we have now if the -NAO remains negative. So some more things to think about as we head into early January. Record December Aleutians Ridge Normal La Niña December composite much weaker January La Niña shift east closer to the West Coast

Models coming in stronger with the -PNA around Christmas. This allows a SE Ridge to form. We have been seeing this more in recent years even with a -NAO. The models correcting stronger with the Aleutians Ridge allows a deeper trough in the Western US. New run Old run

The GFS and been more erratic from run to run with this fast Pacific flow than the Euro and CMC. The Euro and CMC have been much more reliable. I am hoping that this means that the big Euro upgrade fixed some of the storm track issues it was having. 18z 12z

While a few trees were fully leafed out here in SW Suffolk last weekend, NYC is running even later.

The +PNA rise and the 11° Arctic cold In NYC right before the storm made it possible. http://www.meteo.psu.edu/fxg1/NARR/1989/us0104.php#picture 1989-01-04 29 11 20.0 -14.7 45 0 T T 0 1989-01-05 26 11 18.5 -16.0 46 0 0.00 0.0 0 1989-01-06 26 21 23.5 -10.9 41 0 0.43 5.0 T

This is turning out to be one of our longest stretches without a -10 or lower departure. The last -10 or lower day in NYC was July 3rd. We would probably need more ridging out West for some of that -10 or colder Arctic cold in Western Canada to spill east. With the trough in the West, we could probably expect single digit negatives behind the cold fronts. Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 2021-07-03 -14.1

It will be interesting to see how close to +10 the Southern Plains finishes this month.

This was one of the best papers to come out in recent years.

The latest extended GEFS runs may set the record for longest MJO phase 7 this time of year. It’s still holding the convection east Australia right into January. Very extreme marine heatwave in those areas.

There are a few things here. None of the models have been showing what we think of as a traditional +PNA at any time within the effective 2 week period. We had a few attempts to boost heights near California near the end of those 15 day runs. But that keeps getting pushed back. Yesterdays extended runs beyond day 15 had this hint of rising heights near California. But this is beyond the effective range. Speculation then turned to why models were showing these height rises. The MJO going into phase 7 with +AAM was one possibility. I think we all know that any model runs beyond day 15 are fickle. Plus any MJO related effect could be short lived after the MJO wave weakens.

This was our 5th warmest first half of December on record. 7 out of the top 10 warmest years have occurred since the late 90s. It’s a reflection of how December is one of our fastest warming winter months. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Dec 1 to Dec 16 Missing Count 1 2015-12-16 51.8 0 2 2001-12-16 50.4 0 3 1998-12-16 50.3 0 4 1953-12-16 46.4 0 5 2021-12-16 46.2 0 6 2011-12-16 45.3 0 7 2012-12-16 45.0 0 8 1999-12-16 44.7 0 - 1891-12-16 44.7 0 9 1951-12-16 44.6 2 10 1879-12-16 44.5 2

Syracuse just had their 2nd warmest December day on record between the 16th and 31st. Only 1° behind 2015. Three of the top five warmest readings occurred since 2015 RECORD EVENT REPORT NATIONAL WEATHER SERVICE BINGHAMTON, NY 519 PM EST THU DEC 16 2021 ...RECORD DAILY HIGH TEMPERATURE SET AT SYRACUSE NY... A RECORD HIGH TEMPERATURE OF 67 WAS SET AT THE SYRACUSE HANCOCK INTERNATIONAL AIRPORT NEAR MATTYDALE NY TODAY. THIS BREAKS THE OLD RECORD FOR DECEMBER 16TH OF 55 SET IN 1971. Time Series Summary for SYRACUSE HANCOCK INTL AP, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Highest Max Temperature Dec 16 to Dec 31 Missing Count 1 2015-12-31 68 0 2 2021-12-31 67 0 3 1949-1957 66 0 4 2018-12-31 65 0 - 1984-12-31 65 0 5 1964-12-31 64 0

If the changes we are seeing turn out to be MJO driven, then the effects may only last until this MJO wave weakens. All these extended model runs are only a snapshot of what early January may look like. We can’t really extrapolate the whole month from the first 10 days. It’s nearly impossible to make a long range forecast based on another long range forecast.

It looks like the extended EPS moved toward the JMA in early January. It now tries to build a ridge near California. This is a big shift from the run a few days ago. It may be correcting to more of a MJO 7 +AAM look. The model could continue playing catch up like it recently did with the -NAO. So future runs could show further corrections. New run Jan 3-10 Old run

No problem. Allan does a great job with his custom MJO composites. Even if 50% of that 500 mb pattern verified in January, it would probably be 100% better than this month so far.