bluewave

It would look like the composite below. Warmer than average winter temperatures. So we would need bowling ball type closed lows to occasionally undercut the ridge for near to above normal snowfall.

The latest EPS is a great illustration of this. Back and forth between warm ups and cool downs. But the coldest departures go to our south.

There seems to be an inverse correlation between the La Niña strength and our winter weather since 2010. The stronger coupled La Ninas in a two year sequence actually had more snow. But before 2010, it was usually the weaker of the La Ninas which were snowier. Coupled La Niña ONI and NYC snowfall Stronger of two years bolded 17-18….-1.0…..40.9” 16-17…..-0.7….30.2” 11-12…..-1.1……7.4” 10-11…..-1.6…..61.9” 08-09….-0.8….27.6” 07-08….-1.6…..12.4” 05-06…..-0.9…40.0” 00-01……-0.7….35.0” 99-00……-1.7….16.3”

I think the culprit with the recent model forecasts was the record early snow and cold in China. That TPV drop into East Asia is pumping the NPAC ridge up further west. So we get a big WPO drop instead of EPO. This gives the La Niña Jet more opportunities to come ashore out West. So we get this back and forth pattern of warm ups and cool downs. To the EPS weeklies credit, they always showed the core of the cold going to our south.

It’s been tough to get the core of the cold into New England this year. The most recent cool down was focused to our south. Looks like the coming cool down from the weekend into next week will do the same. November so far Forecast Last 12 month period warmest on record in Maine

Even before we see what the NAO does in November, the MJO is giving hints in October. We usually have DJFM -NAO and -AO intervals coming off October Maritime Continent forcing like we saw this year. It’s the odd year with very strong forcing over the Western IO that seems to really set off the polar vortex.

The NAO is currently negative and is forecast to go positive for a time in mid-November. Long range EPS and GEFS have it gong negative again later in the month. The phase of the November NAO for the last 10 out of 11 coupled La Ninas has correctly predicted the NYC seasonal snowfall and winter temperatures. The snowiest and coldest La Ninas had a November NAO under -1 for 1995 and 2010. At this point, the -NAO doesn’t look like it will be that negative. The least snowiest and warmest 2011 had the November NAO above +1. So this November isn’t showing such a positive NAO. If we can maintain a neutral to even slightly negative NAO for the whole month, then NYC will have a reasonable chance of reaching 25” or more of snow this coming season. Winter temperatures could average near to above normal following a NAO in that November range. The new 1991-2020 winter average temperature in NYC has risen to 36.2° from 35.1° for the 1981-2010 period. So this could make it easier for NYC to come closer to normal or have a less warm departure than it would have been using the older averages. https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table November coupled La Niña NAO and NYC seasonal snowfall and DJF average temperature Season………..Nov NAO……Snowfall….Temperature 2017-2018…..0.00….40.9”….36.2° 2016-2017…..-0.16….30.2”….39.3° 2011-2012…..+1.36….7.4”…..40.5° 2010-2011…..-1.62…..51.4”….32.8° 2008-2009…..-0.32…27.6”….34.2° 2007-2008…..+0.58…11.9”….36.4° 2005-2006…..-0.31….40.0”….37.3° 2000-2001…..-0.92….35.0”…..33.5° 1999-2000…..+0.65….16.3”….36.2° 1998-1999……-0.28….12.7”….38.6° 1995-1996…….-1.38….75.6”….32.2°

Not much change in the extended EPS. MJO 4-6 ridging over the NE PAC with the PAC Jet sending shortwaves through from time to time. Warmer this week with a cool down from the weekend into next week. Last week of November has a colder than average area just to our west. But we’ll see what that looks like the closer we get since week 3 and beyond has lower skill. Nov 8-15 Nov 15-22 Nov 22-29

It looks like a back and forth type pattern. The MJO 4-6 is pumping the -EPO/+PNA. But the very strong La Niña Jet acts to flatten it out. So we get a progression of warm ups and cool downs. The monthly departure may not be determined until the last week of November. Maybe the new weeklies later will provide some clues.

Warm up this week after a colder than average first week of November. Looks like our next chance of significant rain and wind will be Friday. Then we start another cool down during the weekend. Probably a leaf clean up weekend after the storm for the garden interests.

Even in our new snowier climate since 02-03, 17-18 stands out in Suffolk. Data for October 1, 2020 through April 30, 2021 Click column heading to sort ascending, click again to sort descending. Name Station Type Total Snowfall NESCONSET 1.4 SSW CoCoRaHS 46.1 MOUNT SINAI COOP 41.3 Data for October 1, 2017 through April 30, 2018 Click column heading to sort ascending, click again to sort descending. Name Station Type Total Snowfall BRIGHTWATERS 0.7 NNW CoCoRaHS 72.0 NESCONSET 1.4 SSW CoCoRaHS 71.8 Data for October 1, 2016 through April 30, 2017 Click column heading to sort ascending, click again to sort descending. Name Station Type Total Snowfall BAITING HOLLOW COOP 42.7 UPTON COOP - NWSFO NEW YORK COOP 42.1 NESCONSET 1.4 SSW CoCoRaHS 41.2 Data for October 1, 2015 through April 30, 2016 Click column heading to sort ascending, click again to sort descending. Name Station Type Total Snowfall ISLIP-LI MACARTHUR AP WBAN 41.4 CENTERPORT COOP 41.0 Data for October 1, 2014 through April 30, 2015 Click column heading to sort ascending, click again to sort descending. Name Station Type Total Snowfall BAITING HOLLOW COOP 67.9 JAMESPORT 0.6 SSW CoCoRaHS 63.9 ISLIP-LI MACARTHUR AP WBAN 63.7 RIVERHEAD RESEARCH FARM COOP 63.5 UPTON COOP - NWSFO NEW YORK COOP 62.2 ROCKY POINT 2.0 N CoCoRaHS 61.6 Data for October 1, 2013 through April 30, 2014 Click column heading to sort ascending, click again to sort descending. Name Station Type Total Snowfall ISLIP-LI MACARTHUR AP WBAN 63.7 BAITING HOLLOW COOP 62.7 CENTERPORT COOP 60.8 Data for October 1, 2012 through April 30, 2013 Click column heading to sort ascending, click again to sort descending. Name Station Type Total Snowfall UPTON COOP - NWSFO NEW YORK COOP 51.1 ISLIP-LI MACARTHUR AP WBAN 46.9 BAITING HOLLOW COOP 45.1 MOUNT SINAI COOP 44.5 Data for October 1, 2010 through April 30, 2011 Click column heading to sort ascending, click again to sort descending. Name Station Type Total Snowfall CENTERPORT COOP 64.0 MOUNT SINAI COOP 55.9 ISLIP-LI MACARTHUR AP WBAN 55.3 BAITING HOLLOW COOP 53.1 NORTHPORT 1.6 NNE CoCoRaHS 52.5 Data for October 1, 2009 through April 30, 2010 Click column heading to sort ascending, click again to sort descending. Name Station Type Total Snowfall BAITING HOLLOW COOP 57.0 EAST MORICHES 0.6 WNW CoCoRaHS 55.0 ISLIP-LI MACARTHUR AP WBAN 53.8 Data for October 1, 2008 through April 30, 2009 Click column heading to sort ascending, click again to sort descending. Name Station Type Total Snowfall BRIDGEHAMPTON COOP 44.3 Data for October 1, 2004 through April 30, 2005 Click column heading to sort ascending, click again to sort descending. Name Station Type Total Snowfall RIVERHEAD RESEARCH FARM COOP 63.8 BRIDGEHAMPTON COOP 59.3 ISLIP-LI MACARTHUR AP WBAN 58.8 CENTERPORT COOP 54.3 Data for October 1, 2003 through April 30, 2004 Click column heading to sort ascending, click again to sort descending. Name Station Type Total Snowfall CENTERPORT COOP 59.7 BRIDGEHAMPTON COOP 47.9 RIVERHEAD RESEARCH FARM COOP 43.5 Data for October 1, 2002 through April 30, 2003 Click column heading to sort ascending, click again to sort descending. Name Station Type Total Snowfall BRIDGEHAMPTON COOP 63.5 RIVERHEAD RESEARCH FARM COOP 48.7

When you see such a big North Pacific pattern change like this, expect the model storm details beyond 5 days to vary more than usual from run to run.

Our last bookend La Niña was 17-18. Snowy mid-December to January 4th then early spring from mid-January through the 80° high in late February. Record snows in March to early April. 16-17 had a very even distribution of snow from December through March. It was really mild from late December through February. We had the famous Denver style 60° the day before the February blizzard. 10-11 was our last front-loaded La Niña winter with Newark recording 60"+ from late December to late January before the snows shut off. Monthly Total Snowfall for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Year Dec Jan Feb Mar Apr Season 2016-2017 3.2 14.0 14.7 7.4 T 39.3 2017-2018 6.0 22.0 1.4 31.9 4.6 65.9 Maximum 35-Day Total Snowfall for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Rank Value Dates Missing Days Period of record: 1931-02-01 to 2021-11-06 1 61.6 2010-12-26 through 2011-01-29 0

The MJO going into phase 4-6 in mid to late November would support a big ridge over Western North America and colder temperatures in the East.

We’ll probably need one of the mid-November storm systems to amplify enough to get our first -10 departure of the fall. The last -10 departures occurred on the July 4th weekend. https://mesonet.agron.iastate.edu/plotting/auto/?_wait=no&q=32&network=NYCLIMATE&station=NYC004&year=2016&var=avg&gddbase=50&gddceil=86&how=diff&cmap=jet&_r=t&dpi=100&_fmt=png

Yeah, 85-86 that was the last colder winter with below average snowfall. Several of the 1980s winters had patterns that haven’t repeated since. December 1980 was our last below zero Christmas. 1982 featured our last April blizzard with 3 daily consecutive record low temperatures. December 1989 was the last -10 departure December that averaged in the 20s.

Our last colder than average winter was 2014-2015. So we have had 6 warmer than normal winters in a row. Be interesting to see if our new warmer 1991-2020 climate normals make it easer to actually get a DJF below normal average temperature one of these winters. Luckily for the snow fans, we have had above normal snowfall for 4 out of those last 6 seasons.

The Euro seasonal DJF 500mb composite is a blend of the 16-17 and 17-18 La Ninas. The SE Ridge/WAR in the means kept those winters warmer than normal. But the poleward Aleutians ridge across the Arctic to Greenland gave us the -AO and -NAO intervals and above normal snows. Be interesting to see if the SEAS 5 comes close to the actual winter pattern.

The October NAO was the 2nd most negative on record for the month. But it was a continuation of the south based blocking like we saw last winter. Notice how much different this October was from the other 4 years below -2. The previous years were El Niño’s rather than the La Niña this year. So it will be interesting to see how things go as we head into December. https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table Top 5 lowest October NAO monthly averages -2.30….1968 -2.29…..2021 -2.28…..2002 -2.24…..2006 -2.06…..2012

Yeah, it still has the +PNA spike. But the SPV is a little stronger this run. So the Atlantic blocking later in November is extending north from east of New England. The last run with the weaker SPV had more Greenland blocking. But these SPV forecast beyond 10 days often change from run to run. So it may very well have another solution next week.

I think the models are going for a ridge over Western North America mid-November due to the MJO 5 La Niña standing wave. November is one of those months that convection near the Maritime Continent can force a ridge in that area. But it’s really uncertain how strong or long such a pattern would last. For later November into December, the blocking will probably determined by the strength of the SPV. And we know how uncertain these model SPV forecasts can be beyond the 6-10 day period. Our weather patterns from last November through the winter were very SPV driven. The very strong SPV in November lead to the record warmth. Then the SPV weakening was associated with the mid-December snowstorm. This was followed by record warmth on Christmas with the SPV rebound. Our best stretch of winter was in February following the major SSW.

What happens with the SPV next few weeks will probably determine how much blocking we get from later November into December.

Continuation of the colder departures further to the south theme. The departures yesterday were colder near DC than New England. We have seen this temperature departure pattern frequently this year. 11-3 departures CAR.…-2 BOS….-3 ISP…….-5 NYC…..-6 DCA……-8 Next several days more of the same Year to date temperature departures

That’s the kind of week 2 cold signal that could lead to a cold departure November if the late month blocking pattern comes to fruition.

That’s what it took to finally erase the persistent warm blob south of Alaska.