bluewave

Yeah, small 1-2 inch events like the other day are nice. But we need the help of multiple warning level snow events for a normal to above normal snowfall season.

December 2013 was a +NAO and -EPO pattern also. My guess is that the warming WPAC is giving us this low frequency forcing pattern. We got a lucky SFWE on 12-13-14. So NYC finished with above normal snowfall in December. But the MJO going into 4-5 spoiled the party with the 70 degree temperatures around the solstice. That was the only reason NYC finished +1 instead of a cold departure. So root for the MJO to stay weak the rest of the month with a lucky SWFE.

I know everyone likes to look at the MJO RMM charts. But sometimes the low frequency forcing can tell the story. Notice the persistent low frequency forcing since the beginning of November over the WPAC. It lines up with a MJO 6 pattern this time of year. You can see this is the December pattern so far with the -EPO and +NAO.

While it has been a cold pattern, the storm tracks have been too warm for much snow at the coast. Looks like we see a continuation of this next week. A few days of warm and wet followed by more cold and dry. NYC is actually behind the snowfall pace of last year. NYC has 1.6”vs 6.4” by December 6th last year.

40 and flurries in SW Suffolk.

The record amount of open water for the Chukchi Sea continues to be one of the big stories this year.

Yeah, the interior Northeast is doing great in this pattern. Must be nice living on an area where the phase of the NAO and AO aren’t as important as the coast for record snows.

None of the models have shown much skill day 11-15 last few weeks. But this -EPO +NAO pattern has been a familiar one in December since 2013. One of the main characteristics has been big temperature swings. Where we alternate between +10’s departure days or higher and -10’s or lower.

Classic December -EPO +NAO pattern. This sets up a duel between the the -EPO ridge and the SE ridge. So we get alternating warm ups and cool downs. Amplified systems cut to the Great Lakes in this pattern. Root for a perfectly timed SWFE if you want to get a nice front end thump.

NYC has done better this decade with snow in November than during the first week of December.This is a big reversal from last decade. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Total Snowfall Dec 1 to Dec 7 Missing Count 2019-12-07 1.6 4 2018-12-07 0.0 0 2017-12-07 0.0 0 2016-12-07 0.0 0 2015-12-07 0.0 0 2014-12-07 0.0 0 2013-12-07 T 0 2012-12-07 0.0 0 2011-12-07 0.0 0 2010-12-07 T 0 Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Nov Click column heading to sort ascending, click again to sort descending. Year Total Snowfall Missing Count 2019 0.0 1 2018 6.4 0 2017 T 0 2016 T 0 2015 0.0 0 2014 0.2 0 2013 T 0 2012 4.7 0 2011 0.0 0 2010 T 0 Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Total Snowfall Dec 1 to Dec 7 Missing Count 2009-12-07 T 0 2008-12-07 T 0 2007-12-07 1.7 0 2006-12-07 0.0 0 2005-12-07 3.5 0 2004-12-07 0.0 0 2003-12-07 14.0 0 2002-12-07 6.0 0 2001-12-07 0.0 0 2000-12-07 0.0 0 Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Nov Click column heading to sort ascending, click again to sort descending. Year Total Snowfall Missing Count 2009 0.0 0 2008 T 0 2007 T 0 2006 0.0 0 2005 T 0 2004 T 0 2003 0.0 0 2002 T 0 2001 0.0 0 2000 0.0 0

This looks like our first decade with the December AO reaching +3 or higher during 5 years. Ridiculous reversal following the record lows in December 2009 and 2010. Something really changed with the December AO and NAO after 2010. Years with AO reaching +3 or higher in December 2019 2016 2015 2013 2011

Battle of many competing influences coming up. Big East Asian Jet extension meets the -EPO. So the have a very fast split flow with an up and down temperature pattern. The question this month will be what happens with the MJO. All the models agree that it is headed for MJO 2. Longer range MJO forecasts are always poor. But every case of a MJO 2 in December since 1975 was followed by a move into phases 4-6. The only difference was the variation in amplitude of those phases. Big temperature swings coming up

That was a very cold -NAO/+PNA pattern for the first week of December 2003. It was the snowiest first week of December and the 11th coldest for NYC.

The state of the NAO/AO/PNA isn’t as important to interior sections of the Northeast as it is to us this time of year. We needed extreme blocking for a Boxing Day Blizzard December high end outcome at the coast.

Sure. I just saw this report from Albany. They can pick up very heavy events this time of year even with a +AO and -PNA. The coast is limited to what it can get this time of year with the lack of good blocking. But even a light event is a really nice way to start December.

Nothing prettier than a fresh snowfall at the beach.

Officially 2 inches of snow on the colder surfaces here in SW Suffolk.

Indications were for a cooler start to December. That much has been obvious for a while. The make or break period for December departures has been mid to late month in recent times. That portion of the forecast is still outside reliable range. Plus long range modeling has been very poor with the raging Pacific split flow.

Another recent paper highlighted how unusual the initiation of the March 2015 unprecedented MJO event in phase 4 was. This helped trigger the 2015-2016 super El Niño event. https://www.nature.com/articles/srep46692 The emergence of this convection–circulation pattern signaled the onset of an MJO that later strengthened to an unprecedented amplitude (MJO real-time multivariate index24 of 4.62 on March 16, 2015 compared with the previous record of 4.02 on February 14, 1985; http://www.bom.gov.au/climate/mjo/) during its eastward propagation over the tropical Pacific in March (Fig. 2c)13. In contrast to the canonical MJOs, which typically originate in the tropical IO, the MJO in spring 2015 initiated in the western Pacific. Our analysis revealed that only 3 out of the 75 large-amplitude MJOs (occurring in 1975, 2013, and 2015; approximately 4%) during 1974–2015 initiated in the western Pacific (i.e., phase 4 of the MJO index24, Supplementary Figure 2). Notably, only in 2015, the MJO preceded the onset of an El Niño event. No eastward-propagating tropical signals from the west but strong extratropical perturbations were observed preceding the 2015 MJO event; this lead–lag relationship implies the potential extratropical effect on triggering the MJO. Furthermore, the percentile values reported in Figs 1 and 2 show the unprecedented amplitudes of the extratropical SLP, northerly, WWB, tropical SLP anomaly crossing the central and eastern equatorial Pacific (Fig. 1c), and the MJO strength. This observation revealed the distinct characteristics associated with this MJO: the effect of extratropical forcing, atypical genesis location and timing, and the extremity of amplitudes in many aspects. The warm ocean surface in the equatorial western Pacific might be another favorable condition conducive to MJO occurrence. A vertical cross section of the monthly ocean temperature along the equator (Supplementary Figure 3) revealed that the upper ocean in the central Pacific was approximately 1.5 K warmer in February–April 2015 than the long-term mean. This warming in the central Pacific was markedly higher than that during the onset of the 1997–98 El Niño. A previous study13 reported the effect of this warm water on MJO development in early spring 2015. An analysis of the SST evolution since early 2014 indicated that the warm SST in the central Pacific was primarily the remaining positive SST anomaly from the aborted 2014 El Niño (data not shown). The extratropical forcing in late February likely triggered the anomalous convection over this warm water and initiated the rigorous atmosphere–ocean interaction in the tropical western and central Pacific and onset of a strong MJO event. Conclusion and Discussion An atypical MJO initiated to the west of the dateline in early March 2015 and rapidly amplified to an unprecedented magnitude over the warm SST in the central and eastern Pacific on March 16. Following the MJO, the SST in the equatorial central–eastern Pacific encountered rapid growth and ultimately evolved to a strong El Niño comparable with the 1982–83 and 1997–98 events. Before the MJO onset, we observed a persisting high-pressure system accompanied by strong cold northerly in the extratropical western North Pacific. On the basis of data diagnostics and numerical experiments, we identified an atypical effect of extratropical perturbations in the western North Pacific on triggering the onset of the MJO in March 2015 and indirectly contributing to the onset of the 2015–16 El Niño. The main results are summarized as follows: 1 Observational analysis indicated that the strong cold northerly, which was associated with a persisting high-pressure system in the extratropical western North Pacific, penetrated southward to the tropical western Pacific and triggered the tropical convective instability that led to the onset of the MJO at an atypical location, namely west of the dateline. The critical effect of the extratropical disturbances on the MJO onset was confirmed by numerical experiments by using an atmospheric general circulation model coupled with an ocean mixed layer model. 2 The MJO developed rapidly to an extreme magnitude because of the favorable ocean conditions: a warm upper ocean temperature in the equatorial central and western Pacific remaining from the aborted 2014 El Niño. 3 Both data diagnostics and numerical experiments revealed that the strong WWB associated with the MJO triggered the first pulse of downwelling Kelvin wave-like perturbations that later induced the onset of the 2015–16 El Niño. Extratropical forcing was the unique characteristic of the reported MJO–El Niño event. The onset of El Niño by an MJO has been observed often. However, according to our review of relevant literature, the present study is the first to report the onset of an El-Niño-inducing MJO in the western Pacific triggered by extratropical perturbations. Extremity was another unique characteristic. Several aspects of perturbations, such as extratropical and tropical SLP, northerly, and the MJO reached unprecedented amplitudes. The reasons for these unique characteristics remain unknown. However, our study revealed the possible effect of extratropical forcing, which has not been considered previously, on the onset of MJO and El Niño. Such a mechanism, although it might not occur frequently, warrants further attention and may elucidate the onset of an MJO and its potential effect on El Niño.

Yeah, this was the easy part of the forecast.

I am close to that bright band on the radar. Just enough of a warm tongue aloft so I am sleet.

Moderate sleet now in SW Suffolk and 33.6 degrees.

https://www.nature.com/articles/s41586-019-1764-4 Article Published: 27 November 2019 Twofold expansion of the Indo-Pacific warm pool warps the MJO life cycle Nature volume 575, pages647–651(2019)Cite this article Article metrics 23 Altmetric Metrics details M. K. Roxy, Panini Dasgupta, Michael J. McPhaden, Tamaki Suematsu, Chidong Zhang & Daehyun Kim Abstract The Madden–Julian Oscillation (MJO) is the most dominant mode of subseasonal variability in the tropics, characterized by an eastward-moving band of rain clouds. The MJO modulates the El Niño Southern Oscillation1, tropical cyclones2,3 and the monsoons4,5,6,7,8,9,10, and contributes to severe weather events over Asia, Australia, Africa, Europe and the Americas. MJO events travel a distance of 12,000–20,000 km across the tropical oceans, covering a region that has been warming during the twentieth and early twenty-first centuries in response to increased anthropogenic emissions of greenhouse gases11, and is projected to warm further. However, the impact of this warming on the MJO life cycle is largely unknown. Here we show that rapid warming over the tropical oceans during 1981–2018 has warped the MJO life cycle, with its residence time decreasing over the Indian Ocean by 3–4 days, and increasing over the Indo-Pacific Maritime Continent by 5–6 days. We find that these changes in the MJO life cycle are associated with a twofold expansion of the Indo-Pacific warm pool, the largest expanse of the warmest ocean temperatures on Earth. The warm pool has been expanding on average by 2.3 × 105 km2 (the size of Washington State) per year during 1900–2018 and at an accelerated average rate of 4 × 105 km2(the size of California) per year during 1981–2018. The changes in the Indo-Pacific warm pool and the MJO are related to increased rainfall over southeast Asia, northern Australia, Southwest Africa and the Amazon, and drying over the west coast of the United States and Ecuador. Fig. 1: A twofold expansion of the warm pool. Fig. 2: Changes in the MJO life cycle. Fig. 3: Correlation between MJO phase duration and ocean–atmosphere conditions. Fig. 4: Changes in global rainfall in response to the changes in MJO phase duration. Extended Data Fig. 1 Typical life cycle of the MJO. Extended Data Fig. 2 Annual average period of MJO events. Extended Data Fig. 3 Warm pool area in multiple datasets and breakpoint analysis. Extended Data Fig. 4 Correlation between MJO phase duration and ocean–atmosphere conditions, without removing the trends.

This matches the pattern pretty well. We can still get record cold as the climate warms. But the ratio of record highs to record lows keeps increasing. Record Arctic outbreaks also occupy a much smaller area now. You can see how the October record cold in the Western US was like a tiny ice cube in a global sea of warmth.

Every month since April has featured top 3 warmth in the Arctic. This is a first for April through October. https://www.esrl.noaa.gov/psd/data/timeseries/