bluewave

We have been getting warmer than average to record warm winters in the Northeast since the super El Niño regardless of ENSO. So El Niño or La Niña may not be that relevant for our temperatures. Snowfall has been highly variable since the 90s with mostly all or nothing seasons. Unfortunately, last winter was one of the nothing seasons for snowfall. Mot much correlation between winter temperatures around NYC and ENSO. NYC Feb 23…+5.2 Jan 23…+9.8 Dec 22…-0.6 …………..+4.8……La Niña…2nd warmest winter Feb 22….+1.4 Jan 22….-3.2 Dec 21….+4.7 ……………..+1.0….La Niña Feb 21….-1.7 Jan 21….+1.1 Dec 20…+1.7 …………..+0.4……La Niña Feb 20…+4.8 Jan 20….+6.5 Dec 19….+0.8 …………….+4.0…..Neutral….7th warmest winter Feb 19….+0.9 Jan 19….-0.1 Dec 18…+2.6 …………….+1.1……Uncoupled El Niño Feb 18…+6.7 Jan 18….-0.9 Dec 17…..-2.5 …………….+1.1……La Niña Feb 17…..+6.3 Jan 17….+5.4 Dec 16….+0.8 …………….+4.2…..La Niña…6th warmest winter Feb 16….+2.4 Jan 16….+1.9 Dec 15….+13.3 …………….+5.9…..El Nino …2nd warmest winter

Both things can be true at the same time. The record WPAC warm pool is providing fuel for the forcing near MJO 4 to MJO 6. The near record Nino 4 SSTs are boosting the forcing near MJO 7. So we are getting a tug of war between competing El Niño and La Niña influences. This pattern translates into a warmer pattern for us in December. The hope is that the MJO 4-6 forcing can fade enough as the season progresses to allow some version of the backloaded El Niño winter climo to emerge. But as Chuck mentioned yesterday, we don’t want La Niña forcing to interfere with the typical El Niño response from later January into February.

Yeah, very Niña-like MJO activity during our last 2 El Niño Decembers.

Tuesday into Wednesday will probably be the coldest readings we see in a while.

The warmest +30C waters are spread out from MJO 4 to MJO 7 near the Dateline. So that’s why we suddenly saw the models correct warmer for early December. Some version of this has been happening most Decembers last decade.

That’s one of the issues with the smoothed out ensemble means for the day 11-15 forecasts. They miss details like the MJO and jet speed. So we end up with a trough closer to West in the newer runs and mild Pacific air across most of North America in early December. New run is warmer due to faster Pacific Jet pushing trough into West Older run cooler for our area with more ridging out West New run Western trough Old run Western ridge

My guess is that the models are picking up on the forcing slowing near the MJO 4-7 regions on VP anomaly charts. Notice how the recent runs have the forcing closer to the warmer phases. This seems to be a regular December occurrence in recent years with models initially trying to rush the warm phases. I like the VP anomaly charts better sometimes since models can really rush the RMM charts leaving the warmer phases. Notice how the new runs of the Euro are correcting stronger with the jet extension near Japan. I believe this much stronger jet tries to knock down the ridge over the Western US. Probably related to that big forcing cell near MJO 4. The silver lining for the general public outside this forum is that heating demand for most of the continent will be below average. So most will be happy to see a break on their heating bills. New run stronger jet extension near Japan Old run much weaker allowed more Western ridging

The blocking is developing but it’s favoring Europe. When we see the polar vortex shift over to Europe, it takes a lot of patience to see improvement here. Notice how there is no real cold air anywhere in North America as we head into December.

The static background state is the expanding record WPAC warm pool leading to stronger and more frequent MJO 4-6 phases and multiyear La Ninas. This can even occur during super El Niños like in December 2015. And we saw how this background state prevented the 18-19 El Niño from coupling. https://www.nature.com/articles/s41558-023-01801-6 Understanding the recent increase in multiyear La Niñas Bin Wang, Weiyi Sun, Chunhan Jin, Xiao Luo, Young-Min Yang, Tim Li, Baoqiang Xiang, Michael J. McPhaden, Mark A. Cane, Feifei Jin, Fei Liu & Jian Liu Nature Climate Change volume 13, pages 1075–1081 (2023)Cite this article 8180 Accesses 188 Altmetric Metrics details Abstract Five out of six La Niña events since 1998 have lasted two to three years. Why so many long-lasting multiyear La Niña events have emerged recently and whether they will become more common remains unknown. Here we show that ten multiyear La Niña events over the past century had an accelerated trend, with eight of these occurring after 1970. The two types of multiyear La Niña events over this time period followed either a super El Niño or a central Pacific El Niño. We find that multiyear La Niña events differ from single-year La Niñas by a prominent onset rate, which is rooted in the western Pacific warming-enhanced zonal advective feedback for the central Pacific multiyear La Niña events type and thermocline feedback for the super El Niño multiyear La Niña events type. The results from large ensemble climate simulations support the observed multiyear La Niña events–western Pacific warming link. More multiyear La Niña events will exacerbate adverse socioeconomic impacts if the western Pacific continues to warm relative to the central Pacific. https://link.springer.com/article/10.1007/s00376-020-0261-x Distinctive MJO Activity during the Boreal Winter of the 2015/16 Super El Niño in Comparison with Other Super El Niño Events Abstract Many previous studies have demonstrated that the boreal winters of super El Niño events are usually accompanied by severely suppressed Madden-Julian oscillation (MJO) activity over the western Pacific due to strong descending motion associated with a weakened Walker Circulation. However, the boreal winter of the 2015/16 super El Niño event is concurrent with enhanced MJO activity over the western Pacific despite its sea surface temperature anomaly (SSTA) magnitude over the Niño 3.4 region being comparable to the SSTA magnitudes of the two former super El Niño events (i.e., 1982/83 and 1997/98). This study suggests that the MJO enhanced over western Pacific during the 2015/16 super El Niño event is mainly related to its distinctive SSTA structure and associated background thermodynamic conditions. In comparison with the previous super El Niño events, the warming SSTA center of the 2015/16 super El Niño is located further westward, and a strong cold SSTA is not detected in the western Pacific. Accordingly, the low-level moisture and air temperature (as well as the moist static energy, MSE) tend to increase in the central-western Pacific. In contrast, the low-level moisture and MSE show negative anomalies over the western Pacific during the previous super El Niño events. As the MJO-related horizontal wind anomalies contribute to the further westward warm SST-induced positive moisture and MSE anomalies over the western tropical Pacific in the boreal winter of 2015/16, stronger moisture convergence and MSE advection are generated over the western Pacific and lead to the enhancement of MJO convection. https://www.climate.gov/news-features/blogs/enso/csi-enso-case-missing-central-pacific-rainfall

Lander, Wyoming hit the snowfall jackpot this month.

My guess is that record +30C warm pool is slowing the forcing down around the Maritime Continent instead of allowing it to move more quickly to the east. New run forcing further west Old run was further east

This is the first time at the start of December that such a strong El Niño had an extensive +30C SST pool from the Maritime Continent to east of the Dateline.

Yeah, we need these day 11-15 favorable Pacific forecast patterns to still be there once we are in the more reliable day 6-10 forecast period. We can remember how the day 11-15 EPS had a favorable Pacific pattern to start December. Now the new day 6-10 is milder than the old day 11-15 since a trough is forecast to dig into the West. New run for December 1st Old run for December 1st

The early February 21 blizzard worked since the upper low lingered in place near the East Coast after the December into January 20-21 +PNA. Plus we got a great Rockies ridge amplification at the time of the storm which was an effective +PNA even if the raw indices had a -PNA. That’s why I am a big fan of using 500 mb anomalies over the raw indices at times. So even though we were technically -PNA at storm time, it was nothing like the raging -PNA we had last winter with the trough digging into the Baja.

I believe the last time a favorable EPS 11-15 forecast this time of year verified in our favor was in 2020.

You were talking about a wintery precip threat a while back for late November. I pointed out to you that we seldom see this with a piece of the trough hanging back to the SW . Any amplified short waves will pump the SE ridge which is what is happening with this storm system. So we only need a SE ridge for 1 day to result in a warmer storm track.

Same old story of recent years with a stronger SE ridge than forecast resulting in a further west storm track. New run Old run

Yet we have some very strong forcing in the MJO 2 to 4 regions along with the Nino itself near the Dateline. It’s why the RMM charts aren’t of much use right now. This is like the atmosphere playing a chord instead of individual Nino or Niña notes. So plenty of competing influences to go around with dueling +30 C warm pools in the WPAC and around the Dateline.

Cruising toward at least our first week at super El Niño levels. Very warm in Nino 3 also. Plus it looks like Nino 4 is approaching the all-time weekly record of +1.7 set in 15-16. https://www.cpc.ncep.noaa.gov/data/indices/wksst9120.for

It will be colder than the lowest November maxes last few years. But the 2019 and 2018 low maxes for the month of November at 34 and 28 should be safe. Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Nov Click column heading to sort ascending, click again to sort descending. Year Lowest Max Temperature Missing Count 2023 44 6 2022 40 0 2021 39 0 2020 36 0 2019 34 0 2018 28 0 2017 38 0 2016 41 0 2015 44 0 2014 36 0 2013 30 0 2012 40 0 2011 46 0 2010 42 0

The surface temperature departures this month have been less impressive than the departures at 850 mb over the Northeast. So while this will probably be our coldest temperatures of the fall so far, probably nothing too out of the ordinary for this time of year.

Yeah, it just makes the last 5 years seem even lower then they were. So we went from the highest 5 year snowfall total to the 7th lowest. These all of nothing snowfall patterns have become the new normal after the record 95-96 season was followed by 8 lowest 5 year snowfall total. Minimum 5-Year Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days Period of record: 1871-01-01 to 2023-11-24 1 66.1 1932-12-31 0 2 66.2 1931-12-31 0 3 71.9 1955-12-31 0 4 72.2 1954-12-31 0 5 74.8 1992-12-31 0 6 77.0 1953-12-31 0 7 77.7 2023-12-31 37 8 79.4 2001-12-31 1 9 81.8 1977-12-31 0 - 77.7 1975-12-31 0

2014 to 2018 is going to be tough to beat for 5 year maximum snowfall since it was probably at least a 100 year event. Maximum 5-Year Total Snowfall for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Rank Value Dates Missing Days 1 269.9 2014-01-01 through 2018-12-31 0 2 256.2 2013-01-01 through 2017-12-31 0 3 227.0 2015-01-01 through 2019-12-31 0 4 223.3 2012-01-01 through 2016-12-31 0 5 219.4 2011-01-01 through 2015-12-31 0 Maximum 5-Year Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Value Dates Missing Days 1 209.4 2014-01-01 through 2018-12-31 0 2 205.2 1914-01-01 through 1918-12-31 2 3 204.9 1892-01-01 through 1896-12-31 3 4 204.3 1893-01-01 through 1897-12-31 3 5 202.1 1944-01-01 through 1948-12-31 0

A record breaking 8 warmer than normal winters in a row since the 15-16 super El Niño. Then we have the December warming trend which has the 2nd half of the month warming faster than the first half. This has lead to to regular 55°+ highs around the solstice from December 17th to 25th every year since 2011. The average December 1-15th high in NYC back in 1981 was around 39.6° and only warmed to 41.0° in 2022 for a rise of +1.4. The December 16-31 average temperature rose much more steeply from 35.2° to 39.0° for a large increase of +3.8°. So the late December average temperature in the 2020s is nearly the same as the early December temperature in the early 1980s. Snowfall has been much more variable and has been in all or nothing mode. Great outcomes from 15-16 to 17-18. Then a significant drop from 18-19 to 22-23. But we did have the great 20-21 season across the region and the January 22 record snows on Long Island. Forecasts for snow need to make it into the 120 hr or lower forecast period to be believable since we have had so many day 6-10 and 11-15 patterns which looked snowy that never verified. NYC Feb 23…+5.2 Jan 23…+9.8 Dec 22…-0.6 …………..+4.8 Feb 22….+1.4 Jan 22….-3.2 Dec 21….+4.7 ……………..+1.0 Feb 21….-1.7 Jan 21….+1.1 Dec 20…+1.7 …………..+0.4 Feb 20…+4.8 Jan 20….+6.5 Dec 19….+0.8 …………….+4.0 Feb 19….+0.9 Jan 19….-0.1 Dec 18…+2.6 …………….+1.1 Feb 18…+6.7 Jan 18….-0.9 Dec 17…..-2.5 …………….+1.1 Feb 17…..+6.3 Jan 17….+5.4 Dec 16….+0.8 …………….+4.2 Feb 16….+2.4 Jan 16….+1.9 Dec 15….+13.3 …………….+5.9 Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Highest Max Temperature Dec 17 to Dec 25 Missing Count 2022-12-25 58 0 2021-12-25 60 0 2020-12-25 61 0 2019-12-25 57 0 2018-12-25 61 0 2017-12-25 55 0 2016-12-25 58 0 2015-12-25 72 0 2014-12-25 62 0 2013-12-25 71 0 2012-12-25 56 0 2011-12-25 62 0 2010-12-25 40 0 2009-12-25 39 0

The warmest temperatures of the whole season came in September this year. Plus we had record heat in late October. Since the 1991-2020 climate normals have warmed so much, we can still have a top 20 warmest summer with only a +0.3 departure at Islip. Monthly Highest Max Temperature for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Year Apr May Jun Jul Aug Sep Oct Season 2023 93 90 91 96 91 97 85 97 Time Series Summary for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2010 74.7 0 2 2022 74.6 0 - 2020 74.6 0 3 1999 74.5 0 4 2016 74.4 0 5 2011 73.9 0 6 2019 73.8 0 7 2021 73.7 0 8 2018 73.5 0 - 2005 73.5 0 9 2013 73.4 0 10 2012 73.3 0 - 1991 73.3 0 11 2015 73.2 0 - 1980 73.2 0 12 1994 73.0 0 - 1966 73.0 0 13 2008 72.9 0 - 1995 72.9 0 14 2006 72.8 0 - 1998 72.8 0 15 2002 72.7 0 - 1973 72.7 0 16 2023 72.6 0 - 1993 72.6 0 - 1988 72.6 0 17 2014 72.5 0 - 1983 72.5 0 18 1969 72.4 0 19 2017 72.2 0