bluewave

Great day to finish any yard clean ups with a top 5 warmest 12-13 in tap. Data for December 13 - NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Max Temperature Min Temperature Precipitation Snowfall Snow Depth 2015-12-13 67 55 0.00 0.0 0 1923-12-13 64 42 0.10 0.0 0 1984-12-13 63 46 0.00 0.0 0 1946-12-13 63 36 T 0.0 0 1919-12-13 61 42 0.07 0.0 0 1990-12-13 60 41 0.00 0.0 0 1968-12-13 60 36 0.00 0.0 0 1949-12-13 60 36 0.17 0.0 0

The models that handle the 500 mb heights near Oregon and general PNA best will get the storm track correct. Bottom line: I'll be really curious to see tonight's MFR sounding. That 500mb height observation will perhaps help give us (and models) a clue where the storm might go later on. 5570m vs 5590m may seem small, but in a nonlinear system those tiny differences grow rapidly!

This storm will push up against one of the strongest 50/50 lows on record.

The next big leap may be AI. https://www.ecmwf.int/en/newsletter/163/news/ai-and-machine-learning-ecmwf ECMWF is currently making a significant effort to support applications of artificial intelligence and machine learning and to identify how such applications may improve numerical weather prediction at the Centre. Many standard methods used by ECMWF scientists on a daily basis can be regarded as examples of machine learning. However, there has recently been a surge in new methods which have the potential to revolutionise the work of operational weather prediction centres. Such methods include the use of deep neural networks, which can learn the dynamics of very complex non-linear systems from data.

Today should be the warmest day of the month so far with widespread 60s. KEWR GFS MOS GUIDANCE 12/13/2020 0000 UTC DT /DEC 13 /DEC 14 /DEC 15 / HR 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12 18 00 X/N 63 37 44 29 40 TMP 51 50 50 55 60 59 53 47 42 40 39 39 41 41 38 37 34 32 30 38 32

I don’t know. But it seems like when you try to fix one model bias or error, it creates another one. The real model data that you want are local model model biases for the individual NWS offices. So you can say x model is having this bias for storms with y teleconnections in place around the NY Bight. But these general model statistics don’t go that local to include elements such as storm track.

They fixed the GFS cold bias with the v16. But now it has a warm bias compared to the other guidance. The 500 MB skill scores are a little lower than the current OP. That being said, I have no idea how it will do with this storm since it’s just 1 case. https://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/

It’s probably more accurate to use the term model biases. Seasonal storm track biases have been well documented. But we would need to use machine learning for real time model bias correction to the forecast maps.

Looks like the 12z EPS was a little more tucked today vs yesterday due to the slightly weaker +PNA. The first really important run should be 12z Sunday when the energy is fully ashore in California. Then we watch to see what type of short term trends develop.

The AO volatility continues to make headlines. This could be one of the greatest +November to -December reversals on record. Notice how a very +AO in November usually carried over to December. The one exception was 1978. 2020 2.419 3.417 2.641 0.928 -0.027 -0.122 -0.412 -0.381 0.631 -0.072 2.086 2015 1.092 1.043 1.837 1.216 0.763 0.427 -1.108 -0.689 -0.165 -0.250 1.945 1.444 2013 -0.610 -1.007 -3.185 0.322 0.494 0.549 -0.011 0.154 -0.461 0.263 2.029 1.475 2011 -1.683 1.575 1.424 2.275 -0.035 -0.858 -0.472 -1.063 0.665 0.800 1.459 2.221 1994 -0.288 -0.862 1.881 0.225 -0.115 1.606 0.351 0.828 -0.084 0.174 1.779 0.894 1978 -0.347 -3.014 0.502 -0.967 0.059 0.635 -0.604 -0.354 -0.099 0.895 2.470 -0.980

The high over New England will really fight to hold on with a -4.5 SD 50/50 vortex. I wonder if this is close to the record for mid-December? 11 500 4815

Plenty of high octane fuel if we can hold that BM track.

We’ll be good to go if these solutions hold once within the NAM’s best range. The NAM has been our go to model for snowfall with the numerous Euro misses in recent years. I can still remember the NAM bringing home the goods on the January 2016 blizzard while the Euro was too suppressed.

The other thing to watch for is coastal flooding. The astronomical tides will be the highest of December this week with the new moon. Unfortunately, The solar eclipse will only be visible in the Southern Hemisphere. All that is needed for moderate coastal flooding is a 2 foot surge. The big high to the north can make this possible creating a gale to possible storm force gradient. A slower track in later runs would also help to pile up the water. https://www.space.com/total-solar-eclipse-2020-preview

Blocking. First the big +PNA spike early in the month and now the strong block near Greenland and the Pole.

That’s not what I am saying. It’s pretty rare for any individual model or ensemble group to nail a winter storm track down from 5 days out. But the models and ensemble members show some PNA spread which is normal. Even among the EPS members, we do better with the members with a stronger ridge near California. It allows the UL to dig closer to the TV instead of GL. The further south the UL digs, the better insurance policy we have against a hugger track. We may have to wait until the UL comes ashore near California tonight into Sunday for a more definitive answer.

We may just have to take it week by week and month by month. Past expectations based on canonical El Niño or La Niña patterns haven’t been working out since 18-19. Too many competing warm SST blobs for the seasonal models to handle. https://www.climate.gov/news-features/blogs/enso/csi-enso-case-missing-central-pacific-rainfall CSI ENSO: The case of the missing central Pacific rainfall Author: Nat Johnson February 28, 2019 As Emily’s most recent post describes, the tropical Pacific Ocean and atmosphere have finally coupled, allowing NOAA to declare that weak El Niño conditions are present. It’s nice to see the atmosphere and ocean in a cooperative mood, but ENSO forecasters are left with a mystery: why did the expected atmospheric response go missing for so long? In this blog post, we’ll put our detective hats on and look for clues.

You can see how many competing influences there were this month in that 500mb height anomaly map. This may be our first December with a configuration like that. No wonder none of the seasonal model forecasts had a look like that. We were discussing in the other thread back in November how unusual the combination of conflicting SST features were. This could be the 3rd winter in a row that a straight ENSO (El Niño-La Nina) based expectation forecast doesn’t work out.

We’ll see if the MJO can weaken by January.

Better +PNA ridge in California this run so the snowier outcome near the coast. New run Old run

The EPS has had the mid-December storm signal for weeks now. But it also had a moderation in temperatures around the solstice. What it missed was the warm up this weekend.

Starting the day with a heavy frost here in SW Suffolk. But there was a very wide temperature spread across Long Island this morning. The breeze off the ocean kept the South Shore beaches 10° to 20° warmer than areas of the island that were able to radiate. Long Island New York CITY SKY/WX TMP DP RH WIND PRES REMARKS Jones Beach N/A 45 N/A N/A SW7G13 N/A Wantagh N/A 32 30 93 NW3 N/A Hempstead NOT AVBL Matinecock Pt N/A 39 N/A N/A SW2 N/A Farmingdale PTCLDY 30 27 88 CALM 30.22R MacArthur/ISP PTCLDY 27 26 96 CALM 30.22R Shirley PTCLDY 28 23 81 CALM 30.23R Mt Sinai Harb N/A 36 N/A N/A S3 N/A Westhampton PTCLDY 20 17 88 NW3 30.24R East Hampton FAIR 24 23 94 CALM 30.22F Southold N/A 28 28 100 SW1 N/A Montauk N/A 36 34 92 CALM 30.24S

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