bluewave

We may continue to get -NAO -AO intervals as long as the troposphere remains uncoupled from the SPV.

We could use a powerful storm like we got at the end of November last year. That system created a big wave breaking event over the North Atlantic. It pumped the -NAO ridge into December.

In addition to the severe potential that Walt outlined, there is a sting Jet-like feature right behind the low. So we could be looking at two rounds of higher winds. The low level lapse rates steepen behind the storm in the CAA which could allow westerly 50-60 mph gusts.

Yeah, that’s why we see the temperature back and forth continuing. The models have been too weak day 10 with the Pacific Jet. Notice how the day 5 has more of an Alaska +EPO trough than the day 10 was forecasting. New 120 Old 240

It looks like a battle between the warmer Alaska +EPO trough and cooler ridge near the US West Coast. So we get a series of Pacific storms with warm ups ahead of them and cool downs behind. The monthly temperature departure may not be decided until the end of the month.

The Southeast is winning the November cold departure battle so far.

Pretty good rotation with the warned cell over Suffolk. https://www.spc.noaa.gov/products/md/2021/md1943.html DISCUSSION...KOKX radar imagery has shown a long-lived rotating cluster of convection moving north from the shelf waters of the Atlantic to the south coast of eastern Long Island. The KOKX VAD wind profile shows intense flow fields with an enlarged hodograph. The main limiting factors are scant buoyancy and very weak lapse rates. Nonetheless, the storm-scale forcing associated with the hybrid rotating cluster of convection may enable the risk for damaging gusts to be realized on a localized basis, as the convection moves north from eastern Long Island into CT over the next 1-2 hours.

I think we have moved into a new background state. One where the reduced sea ice near the Kara and Barents seas interacts with the SPV and Urals ridge. Last November into December was a recent example of how the pattern can dramatically reverse. The same went for December 2015 into January 2016. So that may be why seasonal models in the fall have been so far off with the winter NAO state. Our new winter blocking regimes near Greenland have been linked to that Urals ridge. Before 2003, our winter blocking episodes often didn’t have that connection. So it’s very challenging to try and forecast monthly NAO changes during the winter before they actually occur.

Remember, the models didn’t catch onto the winter forecast last year until December was practically starting. These early to mid November runs can have a type of fall forecast barrier effect. So anything beyond week 2 has very little skill.

Maybe since the new December average temperature has risen to around 40°, near to below normal temperatures will be easier with a supporting pattern. ……1991-2020….1981-2010 NYC…..39.1°……37.5°……+1.6° EWR….38.0°……36.5°……+1.5° LGA…..40.0°……38.2°……+1.8°

Yeah, we just don’t want the consolidated look to the polar vortex in the next frame. But that is outside the effective range. A more elongated vortex with higher heights near Greenland and the Aleutians would be better. Still plenty of time to see how it evolves.

The polar vortex shifts over the Hudson Bay in late November on the extended EPS. So Canada gets colder and we get cool downs behind each Pacific short wave. Our temperatures average near to below normal. We just don’t want the polar vortex consolidating near the Arctic at the start December like the EPS has. While this is something to watch for, the EPS skill at these ranges is very low. NOV 15-22 Nov 22-29

Tough to compete against the record warmth last November. Newark has only reached 70° once so far this month. They tied the record with 7 days last November. Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Month of Nov Click column heading to sort ascending, click again to sort descending. Year Number of Days Max Temperature >= 70 Missing Count 2021 1 20 2020 7 0 2019 0 0 2018 2 0 2017 2 0 2016 2 0 2015 5 0 2014 2 0 2013 1 0 2012 0 0 2011 3 0 2010 0 0 Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Month of Nov Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Max Temperature >= 70 Missing Count 2020 7 0 - 1975 7 0 1994 6 0 - 1990 6 0 - 1953 6 0 - 1931 6 0 2015 5 0 - 2001 5 0 - 1982 5 0 - 1938 5 0

The NAM has 50 mph gust potential near the coast with the heavy convection tomorrow.

A -1 to +1 first 10 days of November feels much colder due to the record warmth in September and October. EWR….+0.6 NYC…..-1.1 LGA….+0.8 JFK….+0.3 ISP…..-0.6 BDR….-0.6 HPN….-1.2

Yeah, we would probably need winter version of what happened in late October. Getting one of the Pacific Jet lows to undercut the south based Atlantic Block. While the airmass would probably be marginal, we were able to do it during the 16-17 La Niña.

This may have been one of the greatest August to November SST drops south of Alaska on record.

This was the first time we had an October PDO drop below -3.00 since 1955. But that’s what happens with record 940 mb lows off the PAC NW Coast. It also pumped the record south based -NAO in October. https://www.ncei.noaa.gov/pub/data/cmb/ersst/v5/index/ersst.v5.pdo.dat Oct 2021 -3.06

We had the strong -PNA with the 16-17 La Niña winter. But the EPO was more neutral that year. 95-96 was the most perfect balance of -NAO and -EPO that we ever had from December through March.

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.