bluewave

I just said it that way since the wave break which is initiating the NAO shift is originating near the East Coast.

It could just be something as simple as the much warmer Gulf Stream east of the Carolinas leading to a stronger Western Atlantic Ridge. The big Western Atlantic Ridge amplification last few days with 60s into the Northeast is preceding the NAO rise going forward. Higher heights near the East Coast usually leads to a trough formation several days later near Icekand.When we had the trough near the East Coast in early December heights were higher near Western Europe and Iceland.

Those were the days with extended December cold when we could get the whole month averaging around 32°. Now all our Decembers are in the upper 30s or the 40s. While we did get some real cold before Christmas 2022 with the NYC single digit lows, there was near 60° warmth before and after so the month on average was still 38.5°. Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. 2022-12-23 58 8 -4.1 2022-12-24 15 7 -25.9 2022-12-25 28 14 -15.7 2022-12-26 29 18 -12.9 2022-12-27 35 29 -4.2 2022-12-28 47 33 4.0 2022-12-29 51 40 9.7 2022-12-30 62 46 18.4 2022-12-31 55 50 17.1

Overall a nice event to start weakening the drought with 1-2 west of NYC and 2-4 east.

It will be interesting to see what happens. My one concern is that the MJO is currently contributing to the pattern rather than running it. We continue to get more of an El Niño influence blending in with the EPAC forcing. While the CFS and EPS have more of a MJO 7 look in early January, the GEFS looks different. So the GEFS doesn’t have a clean MJO signal like the EPS and CFS. Not sure which way it will go at this point since competing influences make the very long range more uncertain. Plus you can see some La Niña influences in the GEFS.

It’s only seasonable since the new 30 year climate normals around NYC are close to 40° in December. Back in the old days seasonable was closer to the mid 30s. We used to get a really cold December around or below freezing once every 5 to 10 years . Now we will make it 14 years without a really cold December.

Looks like the fast Pacific flow continues until further notice. Warm ups ahead of the Great Lakes lows and cool downs behind the storms. This could be a -1 to +1 month that doesn’t get decided + or - until New Year’s Eve.

The WAR was much stronger than forecast back around the start of December. But the Pacific Jet has been very fast also. So the trough couldn’t go negative tilt fast enough for areas west of NYC to get the heavier rains that Long Island is getting. Very northern stream dominant pattern.

So far the stratosphere and troposphere have been decoupled from each other but this can always change down the line. https://bsky.app/profile/drahbutler.bsky.social/post/3lbso7bj5q22r

Tree down in New Hyde Park.

Both the EPS and GEFS have a classic El Niño North American pattern for Christmas with higher temperature departures in Canada than Florida.

The Great Lakes continues to be the place for record snows in recent years.

More like the recent December temperature climatology where the coldest departures relative to the means are in early December and the warmer departures occur mid to late month. This is why we have been getting so many 50s and warmer readings this time of year. But the colder starts to December have prevented the monthly record high from getting challenged of 76° on 12-07-98. Since even in our warmest Decembers like 2015 it’s hard to set a new monthly max later later in the month.

The cold departure from the first week of December continues to get smaller as parts of the area approach record highs in the mid 60s today.

The split nature of the forcing between the WPAC and EPAC along with what you just said may slow the convection closer to Phase 7 in early January. I think that’s why all the extended guidance is showing the colder look then. But the interaction with the EPAC forcing may cause some type of interference or shift after that period.

Yeah, the bottom line when the Nina and Nino influences overlap is a very fast and mild Pacific flow.

Yeah, going from the 2010s to 2020s has been the biggest decadal decline in snowfall that we have seen so far. Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Mean 0.0 T 2.6 4.4 7.1 0.1 T 14.2 2023-2024 0.0 T T 2.3 5.2 T 0.0 7.5 2022-2023 0.0 0.0 T T 2.2 0.1 0.0 2.3 2021-2022 0.0 T 0.2 15.3 2.0 0.4 0.0 17.9 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 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Mean 0.3 1.1 5.3 12.9 11.8 6.0 0.6 37.9 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 Monthly Total Snowfall for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Mean T 0.0 2.5 7.7 7.8 0.6 T 18.6 2023-2024 0.0 T T 3.1 7.8 0.0 0.0 10.9 2022-2023 0.0 0.0 0.4 T 3.0 1.6 0.0 5.0 2021-2022 0.0 T 0.3 31.8 3.3 1.6 0.0 37.0 2020-2021 T 0.0 7.5 1.1 24.9 T T 33.5 2019-2020 0.0 0.1 4.2 2.5 0.0 T T 6.8 Monthly Total Snowfall for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Mean 0.0 0.9 5.9 16.5 12.8 8.2 0.5 44.8 2018-2019 0.0 4.3 T 0.9 3.5 4.1 T 12.8 2017-2018 0.0 T 6.0 22.0 1.4 31.9 4.6 65.9 2016-2017 T T 3.2 14.0 14.7 7.4 T 39.3 2015-2016 0.0 0.0 T 24.8 13.2 3.2 0.2 41.4 2014-2015 0.0 T 0.4 30.2 13.4 19.7 0.0 63.7 2013-2014 0.0 0.3 8.1 25.2 24.5 5.4 0.2 63.7 2012-2013 0.0 4.2 0.6 3.3 31.4 7.4 0.0 46.9 2011-2012 0.3 0.0 T 3.8 0.6 T 0.0 4.7 2010-2011 0.0 T 14.9 34.4 3.9 2.1 T 55.3 2009-2010 0.0 0.0 25.3 6.4 21.7 0.4 0.0 53.8 Monthly Total Snowfall for Boston Area, MA (ThreadEx) Click column heading to sort ascending, click again to sort descending. Mean 0.9 T 5.2 12.2 7.0 0.6 0.2 26.1 2023-2024 0.0 T 0.2 9.0 0.5 T 0.1 9.8 2022-2023 0.0 T 1.0 6.9 3.6 0.9 0.0 12.4 2021-2022 0.0 T 0.4 36.2 15.3 2.1 T 54.0 2020-2021 4.3 T 13.0 5.8 15.3 0.1 0.1 38.6 2019-2020 0.0 T 11.5 3.1 0.5 T 0.7 15.8 Monthly Total Snowfall for Boston Area, MA (ThreadEx) Click column heading to sort ascending, click again to sort descending. Mean 0.1 0.3 6.9 15.8 20.5 8.5 1.0 53.0 2018-2019 0.0 0.1 0.1 2.1 11.6 13.5 T 27.4 2017-2018 0.0 T 9.2 17.8 8.3 23.3 1.3 59.9 2016-2017 0.0 T 5.9 8.9 21.5 10.1 1.2 47.6 2015-2016 T 0.0 0.9 9.5 15.0 4.1 6.6 36.1 2014-2015 0.0 2.6 0.3 34.3 64.8 8.6 T 110.6 2013-2014 0.0 T 11.7 21.8 22.9 2.2 0.3 58.9 2012-2013 0.0 0.4 3.4 5.0 34.0 20.6 T 63.4 2011-2012 1.0 T T 6.8 0.9 0.6 0.0 9.3 2010-2011 0.0 T 22.0 38.3 18.5 1.3 0.9 81.0 2009-2010 0.1 0.0 15.2 13.2 7.0 0.2 0.0 35.7 Monthly Total Snowfall for Philadelphia Area, PA (ThreadEx) Click column heading to sort ascending, click again to sort descending. Mean T T 1.3 4.7 3.6 0.1 0.0 9.7 2023-2024 0.0 T T 8.0 3.2 0.0 0.0 11.2 2022-2023 T 0.0 T T 0.3 T 0.0 0.3 2021-2022 0.0 0.0 T 12.1 0.4 0.4 0.0 12.9 2020-2021 0.0 0.0 6.6 3.0 14.3 0.0 0.0 23.9 2019-2020 0.0 T 0.1 0.2 T 0.0 0.0 0.3 Monthly Total Snowfall for Philadelphia Area, PA (ThreadEx) Click column heading to sort ascending, click again to sort descending. Mean 0.0 0.4 5.8 10.1 10.8 4.9 0.0 31.9 2018-2019 0.0 3.6 0.3 2.6 6.6 4.0 0.0 17.1 2017-2018 0.0 0.0 8.6 4.6 1.4 15.2 T 29.8 2016-2017 0.0 T 0.3 5.7 2.0 7.0 0.0 15.0 2015-2016 0.0 0.0 0.0 22.9 3.3 1.0 0.3 27.5 2014-2015 0.0 T 0.1 4.3 10.6 12.0 T 27.0 2013-2014 0.0 T 11.2 25.9 22.4 8.5 T 68.0 2012-2013 0.0 T 0.4 3.9 2.7 1.3 0.0 8.3 2011-2012 0.3 0.0 0.0 2.5 1.2 T 0.0 4.0 2010-2011 0.0 T 12.7 25.2 6.1 T T 44.0 2009-2010 0.0 0.0 24.1 3.1 51.5 T 0.0 78.7

Yeah, it looks like we are currently on the more Nino-like side of the long range Euro 3.4 plumes.

The warm spots in NJ tomorrow could make it to the mid 60s.

Plenty of extremes in this pattern with the potential to approach December record high pressure near 1048mb in New England.

The Nino-like influence is why the EPS is going +6C to +10C in Canada around Christmas which is usually much colder during La Ninas.

While there is forecast to be a weak low level inversion tomorrow, the models have 50 KT down to 975mb. So any convection could mix down 60 mph+ gusts on Long Island. Also our best rain event probably since last summer. Good low topped squall line potential with plenty of moisture available and highs in the low 60s. GFS Text Sounding | 21 UTC Wed 11 Dec 2024 | Latitude: 41.0000 | Longitude: -72.0000 PRES HGHT TEMP DWPT RELH MIXR DRCT SKNT TWTB TVRT THTA THTE THTV 1002.8 0 14.9 12.9 87 9.4 178 37 13.7 16.5 287.8 314.2 289.4 1000.0 24 15.9 13.6 85 9.9 179 40 14.6 17.7 289.1 317.0 290.8 975.0 240 15.7 14.1 90 10.5 181 56 14.7 17.5 290.9 320.7 292.8 950.0 460 14.5 14.0 97 10.7 184 64 14.2 16.3 291.9 322.4 293.7

My guess is that the Aleutian Low showing up in all the guidance is a response to the forcing developing near 120W to 150W next few days which is classic El Niño. So we will have dual EPAC and WPAC forcing. The WPAC forcing is probably enhancing the Pacific Jet leading to such a dominant northern stream and weaker STJ.

While the forecasts beyond 2 weeks don’t have that much skill, both the EPS and GEFS are trying to show a more Nino-like WWB pattern by early January.

I understand the sentiment when we use terms like luck when dealing with weather patterns. I even used the term the other day when I stated that we got lucky when the MJO went into phase 8 during January 22. But there are mechanisms driving the weather patterns with reasons behind our sensible weather outcomes. From 2010 to 2018 we were in a fantastic pattern for snow along the East Coast. It came down to the Pacific Jet not being overpowering allowing frequent Benchmark storm tracks. There was no shortage of record warmth in snowy winters like 12-13, 15-16, 16-17, and 17-18. But we were able to get cold and snowy storm tracks in warm patterns. Something changed with the Pacific Jet during the 18-19 winter. We started to get stretches when it became overpowering with primary low tracks through the Great Lakes and hugging the East Coast. So we started to see that even during cold patterns the storms were taking warmer tracks for the East Coast. Fast forward to this December and we have been seeing a similar pattern. Great snowfall outcomes for the lake effect zones and much less along the East Coast. Same old pattern of cold arriving after the storms and not being place ahead of the storms. When we are able to get some development near the Benchmark, there is often a low in the lakes forcing the baroclinic zone too far north. So this month so far is featuring a series of ridges and troughs crossing the country with alternating warm ups and cool downs. But the faster Pacific Jet is the underlying pattern leading to less snow along the East Coast even with the windows of cold we have been getting. So we don’t need a sustained much warmer than average pattern for below normal snows. if we take a look at the Pacific Jet anomalies since 2010, there has been an increase since the 18-19 winter. Plus we just saw the models greatly underestimate the Pacific Jet the closer in time we got to the forecast period last few days. December 2022 had one of the greatest December -AO blocks on record with well below normal snowfall. Many places even had a small cold departure for the month.