bluewave

We will need the Aleutians ridge to put up a fight against the record Pacific Jet in December. Notice how the record jet anomalies have been parked over the Aleutians this fall. So models may struggle more than normal beyond 5 days with such a supercharged Pacific Jet.

Big model war on the 0z guidance for early December. The EPS and GEPS are colder with the Aleutians ridge building toward the Arctic. The GEFS is flatter and warmer with a faster Pacific Jet. That poleward Aleutians ridge matches December La Niña climatology more closely since 2000.

The colder day 15 EPS last night is a great example of how MJO sensitive the early December pattern may be. The 0z EPS weakens the MJO rather than the weeklies stronger wave. So this allows the Aleutians ridge to poke up closer to the Arctic. The newer EPS is actually closer to La Niña climo than what the weeklies snowed yesterday. So another example of how we really have to wait until December gets started to see the true atmospheric response will be. The stronger La Niña 5-6 phases usually hold off until after December. New colder run Weaker MJO Older weeklies stronger MJO

As long as NYC gets 3” or more in a coupled La Niña December since the 1995, it usually does well in the seasonal snowfall department. It’s the few years like 2011-2012, 2007-2008, 1999-2000, and 1998-1999 that came up short. Coupled La Ninas since 1995 bolded Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 2020-2021 0.0 0.0 10.5 2.1 26.0 T 0.0 38.6 2019-2020 0.0 0.0 2.5 2.3 T T T 4.8 2018-2019 0.0 6.4 T 1.1 2.6 10.4 0.0 20.5 2017-2018 0.0 T 7.7 11.2 4.9 11.6 5.5 40.9 2016-2017 0.0 T 3.2 7.9 9.4 9.7 0.0 30.2 2015-2016 0.0 0.0 T 27.9 4.0 0.9 T 32.8 2014-2015 0.0 0.2 1.0 16.9 13.6 18.6 0.0 50.3 2013-2014 0.0 T 8.6 19.7 29.0 0.1 T 57.4 2012-2013 0.0 4.7 0.4 1.5 12.2 7.3 0.0 26.1 2011-2012 2.9 0.0 0.0 4.3 0.2 0.0 0.0 7.4 2010-2011 0.0 T 20.1 36.0 4.8 1.0 T 61.9 2009-2010 0.0 0.0 12.4 2.1 36.9 T 0.0 51.4 2008-2009 0.0 T 6.0 9.0 4.3 8.3 T 27.6 2007-2008 0.0 T 2.9 T 9.0 T 0.0 11.9 2006-2007 0.0 0.0 0.0 2.6 3.8 6.0 T 12.4 2005-2006 0.0 T 9.7 2.0 26.9 1.3 0.1 40.0 2004-2005 0.0 T 3.0 15.3 15.8 6.9 0.0 41.0 2003-2004 0.0 0.0 19.8 17.3 0.7 4.8 0.0 42.6 2002-2003 T T 11.0 4.7 26.1 3.5 4.0 49.3 2001-2002 0.0 0.0 T 3.5 T T T 3.5 2000-2001 T 0.0 13.4 8.3 9.5 3.8 0.0 35.0 1999-2000 0.0 0.0 T 9.5 5.2 0.4 1.2 16.3 1998-1999 0.0 0.0 2.0 4.5 1.7 4.5 0.0 12.7 1997-1998 0.0 T T 0.5 0.0 5.0 0.0 5.5 1996-1997 0.0 0.1 T 4.4 3.8 1.7 T 10.0 1995-1996 0.0 2.9 11.5 26.1 21.2 13.2 0.7 75.6

Leaf clean ups will probably run into early December around the area.

Yeah, these delayed falls have become the new normal. The first one I remember seeing this late was 2007. Beautiful fall color now in Central Park.

Yeah, that’s why the Gulf of Maine SSTs continue to run at record high levels. The nearby record SST warmth probably gave a boost to our recent late season historic tornado outbreaks. I noticed that Boston issued another tornado warning earlier today. https://mco.umaine.edu/gom_sst/

This has been our warmest fall on record through November 21st at several stations across the region. Time Series Summary for SUSSEX AIRPORT, NJ Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Sep 1 to Nov 21 Missing Count 1 2021-11-21 57.1 0 2 2017-11-21 56.1 0 - 2011-11-21 56.1 6 3 2015-11-21 55.8 0 4 2007-11-21 55.5 0 - 2005-11-21 55.5 0 5 2014-11-21 55.3 0 Time Series Summary for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Sep 1 to Nov 21 Missing Count 1 2021-11-21 63.6 0 2 2015-11-21 62.6 0 3 1971-11-21 62.5 0 4 1961-11-21 62.4 0 5 2017-11-21 62.1 0 Time Series Summary for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Sep 1 to Nov 21 Missing Count 1 2021-11-21 60.7 0 2 2017-11-21 60.6 0 3 2015-11-21 60.2 0 4 2016-11-21 59.5 0 - 1990-11-21 59.5 0 5 2005-11-21 59.4 0 - 1971-11-21 59.4 0 Time Series Summary for IGOR I SIKORSKY MEMORIAL AIRPORT, CT Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Sep 1 to Nov 21 Missing Count 1 2021-11-21 60.7 0 - 2016-11-21 60.7 0 2 2017-11-21 60.6 0 3 2015-11-21 60.5 0 4 2011-11-21 60.0 0 5 1977-11-21 59.8 0 Time Series Summary for Boston Area, MA (ThreadEx) Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Sep 1 to Nov 21 Missing Count 1 2021-11-21 60.4 0 2 2011-11-21 59.4 0 3 1975-11-21 59.3 0 - 1931-11-21 59.3 0 4 2017-11-21 59.2 0 5 1971-11-21 59.0 0

Next Euro seasonal monthly forecast for the December on the 5th.

All we are really seeing from the 11-15 day ensembles is a snapshot of what the first week of December may look like. It’s tough to extrapolate a whole month from a week 2 forecast. The main December pattern may not come into better focus until we get closer to the start of December.

This is one of the few times this year that the over the top warm pattern got pushed further north and allowed cooler temperatures in the mid-Atlantic to near our area. Most of the year had the coldest departures focused near Texas.

The MJO standing wave near Phase 5 this month is part of the reason that we are seeing a colder pattern in November. Notice how the coldest departures this month are over the Southeast. This is a good match for the MJO 5 standing wave. La Niñas also tend to be cooler in November like I posted at the beginning of this November thread. I also posted how November has been our coldest departure fall month since 2010. So this cooler November pattern is no surprise. Now, December La Niña climo typically has December as the coolest departure month of winter. This is why many seasonal forecasts go cooler in December. But the MJO 5 standing wave in December is a warmer departure pattern in December due to changing wavelengths going into winter. So we don’t want to see the models continuing with such a robust MJO 5 or 6 standing wave forecast for early December. This is a bit unusual for La Ninas since the stronger MJO 5-6 activity usually occurs in January or February like we saw during our last coupled La Niña in 17-18. So it will be interesting to see how the model forecasts evolve over the next 10 days or so for early December. MJO standing wave near phase 5 since early November Current colder November pattern centered in Southeast matches Same MJO with December wavelength changes is warmer

Those early December forecasts from the GEFS and EPS look different from the typical La Niña composite since 2000. December usually has the trough closer to the Great Lakes than the Pacific Northwest. That’s why seasonal forecasts usually have the colder departures during La Niña winters in December and sometimes into mid-January. So we have to see if the models continue this this pattern as we get closer to the start of December.

The latest EPS has the +PNA -NAO until the start of December. Then if goes more -PNA by December 5th with the NAO and AO rising. So we will just have to look for periods down the road when the Pacific Jet backs off a bit and the Atlantic is more cooperative. Euro 240 Nov 30 Euro 360 Dec 5

The North Pacific is just one area that has been experiencing extremes in opposite directions over the last decade. We had the record wall of -EPO +PNA blocking in 13-14 and and 14-15. This fall has experienced record winds with the supercharged Pacific Jet and record storm systems pounding the West Coast.

While it’s still early in the season, this next 588 dm near record block is further south than we normally see this time of year. So while it’s a 4.5 SD event, the NAO and AO don’t really drop that much. I think the block not being able to propagate further north into Greenland is why the AO and NAO is rising heading into December. Last November we had the opposite pattern of the near record positive November NAO and AO falling into December. New run further south block Old run building more into Greenland Forecast for the NAO to rebound in early December

2016-2017 was one of our warmest winters due to the powerful La Niña Pacific Jet. But it was also snowy since we had favorable Atlantic blocking intervals for memorable snowstorms. So hopefully we can do OK in the snowfall department if the winter turns out warm.

The La Niña vortex in the Northeast Pacific this fall has been the strongest on record since the 1990s. The only other La Niña falls that came close were 2016 and 2011. But 2011 had the vortex further north near Alaska. This year is further south near the Pacific Northwest like 2016. The fall blocking near Greenland this year is closer to 2016 than 2011. So it’s important to see where the La Niña vortex sets up in December and how much blocking we get on the Atlantic side. Long range guidance is hinting that the Niña vortex may try to move over to the -PNA region.

With the colder -NAO+PNA pattern for the rest of the month, November will follow the recent theme of having the coldest monthly departure of fall. EWR….+1.5 NYC….-0.3 LGA…+1.4 JFK….+0.9 ISP…..+0.2 BDR…-0.2 HPN..-0.3

NYC average DJF 30 year climate normals…. 1991-2020….2020s….36.2 1981-2010…..2010s….35.1 1971-2000…..2000s…34.7 1961-1990…..1990s….33.9 Cold departure winters bolded Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Season Mean Avg Temperature Missing Count 2020-2021 36.1 0 2019-2020 39.2 0 2018-2019 36.3 0 2017-2018 36.2 0 2016-2017 39.3 0 2015-2016 41.0 0 2014-2015 31.4 0 2013-2014 32.9 0 2012-2013 36.8 0 2011-2012 40.5 0 2010-2011 32.8 0 2009-2010 33.8 0 2008-2009 34.2 0 2007-2008 36.4 0 2006-2007 36.5 0 2005-2006 37.3 0 2004-2005 35.4 0 2003-2004 32.4 0 2002-2003 31.2 0 2001-2002 41.5 0 2000-2001 33.5 0 1999-2000 36.2 0 1998-1999 38.6 0 1997-1998 39.6 0 1996-1997 37.8 0 1995-1996 32.2 0 1994-1995 37.1 0 1993-1994 31.1 0 1992-1993 35.0 0 1991-1992 37.2 0 1990-1991 39.1 0

Yeah, those were the last cold winters since our snowier era began in 02-03. Colder than normal winters bolded Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Season Mean Avg Temperature Missing Count 2020-2021 36.1 0 2019-2020 39.2 0 2018-2019 36.3 0 2017-2018 36.2 0 2016-2017 39.3 0 2015-2016 41.0 0 2014-2015 31.4 0 2013-2014 32.9 0 2012-2013 36.8 0 2011-2012 40.5 0 2010-2011 32.8 0 2009-2010 33.8 0 2008-2009 34.2 0 2007-2008 36.4 0 2006-2007 36.5 0 2005-2006 37.3 0 2004-2005 35.4 0 2003-2004 32.4 0 2002-2003 31.2 0

We’ll have to wait and see what happens after the the colder period with blocking from late November into early December. The extended EPS goes -PNA by the 2nd week of December. But that is still way out there for the extended EPS accuracy. Nov 29-Dec 6 Dec 6-13

While we get a strong -NAO/-AO block next week, it’s becoming more south based than the models were indicating several days ago. A block approaching 588 dm south of Greenland is near record levels for this time of year. But like we have seen since last winter, these blocks extending south to New England aren’t as cold as the traditional Greenland blocks. New run Old run South based blocking dominating since last winter

The Southeast will have departures approaching -20 before Thanksgiving.

Continuation of the coldest departures going to our south on the latest extended EPS. Looks like the -AO and -NAO peak during the last week of November before weakening in early December. But the +EPO La Niña influence remains constant. November 22-29 Nov 29-Dec 6