bluewave

It could mean climate model studies that show a more -NAO and others a +NAO could both be correct. A corals study that came out in 2009 indicated that the NAO has exhibited wider swings as the climate has warmed. The last 10 years since this study came out featured record -NAO/-AO and +NAO/+AO intervals. We have never seen a decade with such wild swings from record highs to record lows. https://www.sciencedaily.com/releases/2009/01/090113101200.htm Swings In North Atlantic Oscillation Variability Linked To Climate Warming Date: January 14, 2009 Source: Woods Hole Oceanographic Institution Summary: Using a 218-year-long temperature record from a Bermuda brain coral, researchers have created the first marine-based reconstruction showing the long-term behavior of one of the most important drivers of climate fluctuations in the North Atlantic. Using a 218-year-long temperature record from a Bermuda brain coral, researchers at the Woods Hole Oceanographic Institution (WHOI) have created the first marine-based reconstruction showing the long-term behavior of one of the most important drivers of climate fluctuations in the North Atlantic. The North Atlantic Oscillation (NAO) is a wide-ranging pressure seesaw that drives winter climate over much of North America, Europe and North Africa. Past reconstructions of the NAO have relied mainly on terrestrial, or land-based records, such as tree ring chronologies combined with ice cores and historical climate data. Those records do not fully capture oceanic processes linked to NAO variability, and short instrumental records from relatively few locations limit the understanding of ocean–atmosphere dynamics with regard to NAO behavior. “By analyzing the coral, we were able to look at changes in the ocean relative to changes on land,” said Nathalie Goodkin, lead author of the study published in the December issue of the journal Nature Geoscience. “Because they are slow growing and have long life-spans, corals can provide high resolution records that are well dated and centuries long.” As they grow, corals accrete seasonal and annual growth layers, similar to tree rings. The proportions of trace elements versus the major element (calcium) found in the layers of the skeleton largely depend on the temperature of the seawater in which it was formed. By analyzing the strontium to calcium ratio in the Bermuda brain coral, Goodkin and colleagues — WHOI scientists Konrad Hughen, Scott Doney and William Curry — were able to reconstruct monthly changes in ocean temperatures and evaluate variability of the NAO during both cold and warm periods from the Little Ice Age (1800–1850) to modern day. The research team found the variability of the NAO decade-to-decade (multi-decadal scale) has been larger, swinging more wildly, during the late twentieth century than in the early 1800s, suggesting that variability is linked to the mean temperature of the Northern Hemisphere. This confirms variability previously reported in past terrestrial reconstructions. “When the Industrial Revolution begins and atmospheric temperature becomes warmer, the NAO takes on a much stronger pattern in longer-term behavior,” said Goodkin. “That was suspected before in the instrumental records, but this is the first time it has been documented in records from both the ocean and the atmosphere.” The North Atlantic Oscillation is described by the NAO index, calculated as a weighted difference between the polar low and the subtropical high during the winter season. (For more information about the NAO index, see animation.) In a positive phase, both the low-pressure zone over Iceland and high pressure over the Azores are intensified, resulting in changes in the strength, incidence, and pathway of winter storms crossing the Atlantic. In a negative phase, a weak subtropical high and a weak Icelandic low results in fewer and weaker winter storms crossing on a more west-east pathway. The NAO index varies from year to year, but also exhibits a tendency to remain in one phase for intervals lasting more than a decade. An unusually long period of positive phase between 1970-2000 led to the suggestion that global warming was affecting the behavior of the NAO. “Anthropogenic (human-related) warming does not appear to be altering whether the NAO is in a positive or negative phase at multi-decadal time scales,” said WHOI paleoclimatologist Konrad Hughen. “It does seem to be increasing variability. Clearly, this has implications for the future.” “As temperatures get warmer, there’s potential for more violent swings of the NAO — the phases becoming even more positive and even more negative,” Hughen added. “If the NAO locks more into these patterns, intense storms will become more intense and droughts will become more severe.” The climatic influence of the NAO extends from the eastern United States to Western Europe, impacting human activities such as shipping, oil drilling, fisheries, hydroelectric power generation and coastal management. Improving the ability to predict shifts in the phase and intensity of the NAO is a prerequisite to mitigating the economic impacts of future climate change. While additional modeling and palaeoclimatic studies are needed, a broad distribution of marine records could advance our knowledge of NAO variability and serve to improve future projections, said Goodkin, now an assistant professor in the Department of Earth Sciences at the University of Hong Kong. A WHOI Ocean and Climate Change Institute Fellowship, and grants from the National Science Foundation and Woods Hole Oceanographic Institution supported this work.

This almost reminds me of how quickly the Kara Barents block built back across the North Pole to Greenland at the end of December 2015. We had an intense PV that December with the historic warmth and near record +AO. It suddenly reversed at the end of the month. We saw a near record +AO and PV this November with the record warmth. There have been some recent studies linking that KB block to the low sea ice. At the beginning of the month, it was one of the strongest +PNA rises that we ever saw during a moderate La Niña December. So we are getting several overlapping influences all at the same time. https://advances.sciencemag.org/content/4/7/eaat6025 A stratospheric pathway linking a colder Siberia to Barents-Kara Sea sea ice loss View ORCID ProfilePengfei Zhang1,2,*, View ORCID ProfileYutian Wu2, Isla R. Simpson3, Karen L. Smith4, Xiangdong Zhang5, View ORCID ProfileBithi De1 and Patrick Callaghan3 See all authors and affiliations Science Advances 25 Jul 2018: Vol. 4, no. 7, eaat6025 DOI: 10.1126/sciadv.aat6025 Article Figures & Data Info & Metrics eLetters PDF Abstract Previous studies have extensively investigated the impact of Arctic sea ice anomalies on the midlatitude circulation and associated surface climate in winter. However, there is an ongoing scientific debate regarding whether and how sea ice retreat results in the observed cold anomaly over the adjacent continents. We present a robust “cold Siberia” pattern in the winter following sea ice loss over the Barents-Kara seas in late autumn in an advanced atmospheric general circulation model, with a well-resolved stratosphere. Additional targeted experiments reveal that the stratospheric response to sea ice forcing is crucial in the development of cold conditions over Siberia, indicating the dominant role of the stratospheric pathway compared with the direct response within the troposphere. In particular, the downward influence of the stratospheric circulation anomaly significantly intensifies the ridge near the Ural Mountains and the trough over East Asia. The persistently intensified ridge and trough favor more frequent cold air outbreaks and colder winters over Siberia. This finding has important implications for improving seasonal climate prediction of midlatitude cold events. The results also suggest that the model performance in representing the stratosphere-troposphere coupling could be an important source of the discrepancy between recent studies.

Thanks. Maybe the record off equator SST warmth in the North Pacific for a La Niña is also giving us a blocking assist. https://www.aos.wisc.edu/~dvimont/MModes/PMM.html

We need the block to press hard enough so the low tracks out near the benchmark. That would put the coast in a great spot for some of the higher accumulation potential. But a track a little too close to the area would focus the higher accumulations near or north of I-80. So plenty for the models to work out over the next week. My guess is that the snowfall accumulation from this storm in NYC could determine the snowfall outcome for the entire season. La Niña winter snowfall has been very sensitive in NYC to December snowfall. The 3 inch number has been pretty important. Over or under that amount in December has predicted how the snowfall would go for the rest of the season. It may be that a strong enough block in December for a significant 3.0”+ snowfall signals further winter or early spring blocking. La Niña years highlighted 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 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

You have to wonder if that block suddenly getting stronger close to the Siberian Arctic got an assist from the record warmth and low sea ice. New run Old run

Another big warm up into the weekend following some days that were slightly below normal. So the first 2 weeks of December will average warmer than normal. Very little cold air around following the 4th warmest November on record for the CONUS. KNYC GFSX MOS GUIDANCE 12/10/2020 0000 UTC FHR 24| 36 48| 60 72| 84 96|108 120|132 144|156 168|180 192 THU 10| FRI 11| SAT 12| SUN 13| MON 14| TUE 15| WED 16| THU 17 CLIMO X/N 52| 40 53| 46 57| 52 59| 39 47| 33 42| 38 47| 44 47 30 43

Looks like Newark was the big local ASOS winner. SNOWFALL (IN) TODAY 0.3

Steady light snow in SW Suffolk and 35°.

NYC down to .50 mile vis in snow. https://mesowest.utah.edu/cgi-bin/droman/mesomap.cgi?state=NY&rawsflag=3 12:31 34.0 28.0 31.7 79 6.9 17.3 29.63 29.80 Snow 0.50 2300 0.00

It’s normal for the SE Ridge to rebound once we lose the +PNA.

The SE Ridge is making an appearance with the warm up going into the weekend.

Yeah, they are great. We have a bunch of them around here. I like them better than all the windmill palms that have been popping up in the area. https://www.bbg.org/news/bloom_alert_crape_myrtle http://www.islandwidepalmtrees.com/windmill-palms.html

Time Series Summary for Caribou Area, ME (ThreadEx) warmest winters Click column heading to sort ascending, click again to sort descending. Rank Season Mean Avg Temperature Missing Count 1 2015-2016 21.5 0 2 2009-2010 21.1 0 3 2001-2002 19.2 0 4 2019-2020 17.9 0 5 1959-1960 17.8 0 Time Series Summary for Caribou Area, ME (ThreadEx) - Oct through Sep snowiest seasons Click column heading to sort ascending, click again to sort descending. Rank Season Total Snowfall NYC 1 2007-2008 197.8 11.9 2 1954-1955 181.1 11.5 3 2018-2019 165.4 20.5 4 1981-1982 159.8 24.6 5 1972-1973 153.0 2.8 6 2019-2020 151.9 4.8

Wild snow cover swing for North America. We went from the highest in October to the lowest today.

Warmest first week of December on record for Caribou at +13.6. We would have done better in the snowfall department if we had a colder start like last year. The departures in our area ranged from +0.6 at EWR to +2.9 at BDR.

Following several says of slightly cooler than average temperatures, we will rebound back to 50s. Notice how the day 10 guidance was biased too cold again. So a continuation of the ridge over the area verifying stronger than forecast. KNYC GFSX MOS GUIDANCE 12/07/2020 0000 UTC FHR 24| 36 48| 60 72| 84 96|108 120|132 144|156 168|180 192 MON 07| TUE 08| WED 09| THU 10| FRI 11| SAT 12| SUN 13| MON 14 CLIMO X/N 41| 30 41| 33 45| 38 49| 39 49| 44 56| 49 54| 38 42 31 44 New run Old run

Without some kind of record -EPO or -NAO blocking, we can’t get cold winters anymore. 09-10, 10-11, 13-14, and 14-15 were our only 4 cold winters out of the last 11 years. 09-10 to 10-11 was the strongest -NAO of 187 years that I posted earlier. 13-14 and 14-15 featured the record -EPO patterns. The -EPO developed during the summer of 2013 and intensified during November and carried into the next spring. 14-15 saw a similar extreme -EPO combined with El Niño for the backloaded cold. But since the super El Niño in 15-16, all our winters have been warm with intervals when the unfavorable MJO phases ran the table. Some winters like the 18-19 and 19-20 featured the unfavorable MJO phases dominating for warmth and lack of snow. 15-16 to 17-18 had the unfavorable MJO for warmth but we got intervals of blocking for snowy outcomes. Papers on our only cold recent winters: Winter 2009/2010 temperatures and a record‐breaking North Atlantic Oscillation index https://rmets.onlinelibrary.wiley.com/doi/10.1002/wea.660 The North American winter ‘dipole’ and extremes activity: a CMIP5 assessment https://rmets.onlinelibrary.wiley.com/doi/10.1002/asl2.565

You ask a very good question. As recently as 17-18, portions of Long Island had over 60” of snowfall on the season. But this was also accompanied by record warmth and our first 80° reading on record for February. The record MJO actually had an influence on both. We got the extreme February warmth with a SSW. This was followed by the record snow in March. It turns out that strong MJO phases 5-7 can also lead to SSWs. But this isn’t always the case. So it can just as easily be warm without the snow like we saw last winter with the warm MJO phases. We can also see the MJO in the expanded IO warm pool become more active in phases 1-3 with the record IOD like last November. This may have contributed to the record polar vortex last winter. http://s2sprediction.net/file/documents_publications/wcd-2020-17.pdf Mechanisms and predictability of Sudden Stratospheric Warming in winter 2018 Finally, a composite analysis suggests that teleconnections associated with the record-breaking MJO phase 6 observed in the late January 2018 likely played a role in triggering this SSW event. https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/asl.1005 3.1 The winter 2019/20 NAO and November 2019 IOD

The 10-11 winter was all about a continuation of the 187 year record -NAO pattern that began in 09-10. So the record -NAO had a greater influence than the MJO. We can remember how unfavorable the Pacific was from December 1-25 with all the fantasy snowstorms that showed up with the -PNA. But the -NAO set a record 500 height height anomaly in late December. This allowed a retrogression in heights boosting the PNA and setting up the record 60 inches of snow from late December to late January. But once the blocking faded in early February, we began to move toward a more +EPO +NAO that dominated the 11-12 winter. https://rmets.onlinelibrary.wiley.com/doi/10.1002/wea.660 In conclusion, the winter of 2009/2010 was notable for the record negative NAO index in the 187‐year record of Jones etal. (1997), indicating the very unusual nature of atmospheric circulation over the Atlantic/European region. Despite 2009/2010 being a cold winter over the UK and Europe, it was actually around 0.5 to 1 degC warmer than might have been expected given this extreme pattern of atmospheric circulation. Considering observations averaged across the globe, winter 2009/2010 was one of the warmest on record.

Several slightly cooler than average days coming up before another rebound back into the 50s. Pacific flow will dominate with the models adjusting for a stronger +EPO. Same theme of long range guidance being biased too cool and showing too much blocking. KNYC GFSX MOS GUIDANCE 12/06/2020 0000 UTC FHR 24| 36 48| 60 72| 84 96|108 120|132 144|156 168|180 192 SUN 06| MON 07| TUE 08| WED 09| THU 10| FRI 11| SAT 12| SUN 13 CLIMO X/N 43| 30 41| 29 39| 32 43| 38 54| 41 50| 46 57| 51 55 31 44

3-21-18 was the last time that a the coast had heavier totals than inland. https://www.weather.gov/okx/storm03212018

https://www.weather.gov/aly/1-3Dec2019Snow Overview A major winter storm impacted eastern New York and western New England December 1-3, 2019. Snowfall began during the late morning and early afternoon of the 1st ahead of a weakening low pressure system approaching from the western Great Lakes. Snowfall rates of 1-2" per hour occurred from the afternoon into the evening, with the heaviest along the I-90 corridor. As the primary low pressure system weakened, it transferred its energy to a coastal low, which strengthened as it remained nearly stationary for much of the 2nd. This allowed snow to continue to accumulate throughout the day. As the low finally pulled away late on the 2nd into the early morning hours of the 3rd, one final heavy snow band crossed the area before the snow finally pulled out prior to daybreak on the 3rd. Storm total snowfall amounts were heaviest in the central Mohawk Valley, Helderbergs, northeastern Catskills, Capital District, southern Vermont, and the Berkshires, where totals of 18-28" were common. The 22.6" recorded at Albany International Airport made this the 8th largest snowstorm on record, the 4th largest December storm, and the largest since the March 1993 superstorm. It snowed for 39 hours and 14 minutes consecutively. Many schools were closed for two consecutive days, and numerous flights were delayed or cancelled. The governor declared a state of emergency for several of the hard-hit counties, and deployed the National Guard to assist in cleanup efforts. Speed restrictions were also placed on area interstate highways. Amounts of 8-18" were common elsewhere, except for southern portions of Dutchess and Litchfield Counties due to warmer temperatures and mixed precipitation, and northern portions of Herkimer, Hamilton, Warren, and Washington Counties which were on the fringe of the heavier precipitation.

The +EPO continues to beat expectations.

That’s why I was pointing out since late November to view those 300+ hr eps forecasts with caution. The EPS skill falls off pretty quickly after the 7-10 day period. But you could see the more Niña-like Maritime continent MJO forcing coming up. Now the EPS is starting to correct for that 7-8 days out with the more +EPO pattern. New Forecast Old Forecast

It’s not persistent forecasting. It’s persistent patterns. Notice how this is the 2nd December in a row with a big storm during the first week of the month. Early last December a low went south of Long Island and produced record snowfall amounts to our north. Just a variation on the same theme. The heaviest snowfall axis this time will be further east into New England. https://www.washingtonpost.com/weather/2019/12/03/northeast-starts-dig-out-after-snowstorm-drops-more-than-two-feet-spots/ 12-02-19