bluewave

The fast Pacific flow and lack of blocking didn’t allow the cold high to stay anchored over New England. The WAR flexed just enough so the thermal gradient got pushed north of NYC. So these features negated the usual colder influence we see with lows tracking south of Long Island. Plus the low was strung out on a N-S axis without enough deepening near the benchmark to allow the cold air to wrap in behind the storm.

Continuation of the Great Lakes cutter, I 78 to I-84 hugger rain-snow line, and suppressed Southern Stream storm tracks since 2018-2019. Very persistent over-amped Northern Stream of the Pacific Jet. Makes you wonder what it’s going to take to shift this pattern?

Yeah, we have seen a record expansion of the Aleutian ridge since 1980. Some years the axis is further west near the Aleutians. Other years the ridge is displaced further east over the NE PAC and or Canada.

I am glad that my early October indicator pointing to a more -PNA worked out again this year. Was expecting a decline in the PNA from the record levels last year. But we always have to wait until December in order to get the specific value. This is why Canada into the Northern Tier are so much colder than last December.

That smaller part is a representative subset of the wider Atlantic part of the Arctic which is also at record lows for the date. You can see record daily lows extending over to Svalbard on the Atlantic side of the Arctic. Due to geography and season, the September records have been more Pacific focused like in September 2012. So the record lows on the Atlantic side caused the entire Arctic to have a record low Jaxa extent on December 2nd. The extent is the lowest on record for the date at -425K below the previous record set in 2016. Winter records are usually more on the Atlantic side over the years since it’s easier to have open water extending into the Barents and Kara seas due to Atlantification of the Arctic. There is a much narrower opening to the Arctic near Alaska so it’s easier for the area north of Alaska to freeze over by this time of year. Wider Arctic low matches regional lows across the Arctic.

While we couldn’t make any progress with the persistent warm storm track pattern next few days, at least we are finally getting an Arctic outbreak focused right over the Northeast Friday morning.

Another case of the Arctic sea ice record lows occurring outside of the annual minimum period in September since 2012.

The split forcing that I mentioned is preventing s clean MJO 8 response due to the interference leading to a moderation of the pattern mid month on the EPS. https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf The MJO resumed its eastward propagation while greatly strengthening in amplitude over the Western Pacific during the past week. • RMM observations currently show the signal at greater than 3 standard deviations in amplitude, the highest registered since March, 2024 • Based on objectively wave filtered upper-level velocity potential anomalies, the recent strengthening is likely tied to higher frequency wave modes constructively interfering with both the enhanced and suppressed MJO envelopes. • The strong Western Pacific MJO has led to a weakening of the La Nina background circulation over the equatorial Pacific, with convective anomalies developing off the equator. • As the faster propagating tropical variability moves away of the slower MJO envelopes, a transition towards more competing interference is favored, resulting in a substantially weakened MJO signal over the Western Hemisphere during the next two weeks. • Even with a weakened MJO, subseasonal forcing still favors the greatest chances for tropical cyclone development over the South Pacific, with lowered chances over the Indian Ocean. • The extratropical response associated with Western Hemisphere MJO events during December historically consists of development of high latitude blocking over/near Greenland, potentially allowing for Arctic air to be advected into portions of the central and eastern CONUS.

The EPS has been handling this pattern pretty well over the last week or so. It has been fairly steady with the MJO 6 500 mb pattern dominating. Longer duration MJO 6 patterns tend to show a poleward shift with more ridging returning to Plains and East after the first 10 days. This matches the moderation the EPS has been showing in the pattern for mid month. So the first 10 days or so will probably be the coldest part of December relative to the means.

It’s climo for recent gradient patterns no matter what winter month it is. We warm up enough for mostly rain near the coast with amped systems. This was the case last February. But since February is colder we were able to get a little more snow on the front end before the changeover.

A new tropical oscillation called the TWISO has been recently discovered. So maybe the reason we are getting a strong MJO 6 gradient pattern in early December is somehow related to it being out of phase with the MJO. Plus the split forcing between the Maritime Continent and the Western Hemisphere could also be creating an interference pattern. Models showing a MJO 6 interference gradient pattern in early December https://www.pnas.org/doi/10.1073/pnas.2511549122 The tropical climate variability is characterized by various oscillations across a range of timescales. Oscillations that imprint the tropical mean state are generally attributed to slow processes, such as the seasonal cycle or interannual variability. Here, we identify a pronounced tropics-wide intraseasonal oscillation (TWISO) in satellite observations and reanalyses. This oscillation, with a period of 30 to 60 d, is evident across multiple variables and involves interactions between convection, radiation, surface fluxes, and large-scale circulation. It is primarily manifested as convective perturbations in the tropical Indo-Pacific warm pool accompanied by oscillations in the large-scale tropical overturning circulation. Here, we examine the relationship between TWISO, the Madden–Julian Oscillation (MJO), and the instability of radiative-convective equilibrium. Certain phases of TWISO coincide with specific phases of the MJO, suggesting a potential connection between the two. However, although the MJO can amplify the oscillation amplitude of TWISO, it is not essential for TWISO to occur. Finally, due to its broad manifestation across the tropics, TWISO potentially exerts widespread influence on tropical weather and climate at regional scales.

That being said, gradient patterns in recent years have been setting up just north of NYC. We haven’t been near a gradient pattern jackpot zone since February 2014 and 1994. The WAR amps just enough on the storm days and the highs move east of New England. This is what the current models runs are showing for early December.

I am hoping we can get follow up storm systems tracking south of Long Island in the coming weeks and months when it’s colder. We saw a storm take a similar track on 12-5-20 to our south with mostly rain along the coast. With very amped systems early in the season we need strong Arctic high pressure over New England like we got back on 11-15-18.

Big story this year continues to be the strong W to NW flow behind the lows racing by to our north. So far this year has had 63 days at Newark with wind gusts reaching 40 mph or higher. This resulted in the impressive sieche on Lake Erie