bluewave

At least this -NAO is paying off for parts of Europe. Much easier to put together a record snowfall when an unfavorable Pacific can’t impact your pattern. Shows how just a -NAO can be a big influence for Europe. The AEMET weather agency described the situation as "exceptional and most likely historic". Earlier in the day, children in Madrid could be seen hurling snowballs or playing under snow-covered palm trees, while others snapped photos of the rare whiteout which began in earnest the day after Spain celebrated King's Day -- or Epiphany.

Models are correcting more positive with the EPO for later in the month. This is telling us that the models continue to underestimate the strength of the Pacific Jet. That’s why the EPS are warmer than the GEFS during week 2.

That firehose Pacific Jet won’t be denied. The combo of that Jet and the south based block is suppressing the southern stream. So all the precip is PAC NW and SE.

NYC generally needs a cold winter to get more than 1 event of 10” or more in a single season. The last time this happened was during the cold winters of 13-14, 10-11, 09-10, and 03-04. But one of these days, NYC will eventually get 2 events in a mild winter. https://www.weather.gov/media/okx/Climate/CentralPark/sixplussnow.pdf 12-17-20...10.5 1-24-16.....27.5 2-13-14....12.5 1-22-14....11.5 2-8-13......11.4 1-26-11.....19.0 12-26-10....20.0 2-25-10.....20.9 2-10-10......10.0 12-20-09.....10.9 2-12-06......26.9 1-22-05.......13.8 1-28-04.......10.3 12-5-03.........14.0 2-17-03.......19.8 12-30-00......12.0

We may need a loop like March 1888. Ideally, it would occur a little further east than in 1888. While we have less Arctic air now, the SSTs and moisture content would be higher. So lower ratio with more total liquid equivalent. https://www.wunderground.com/blog/weatherhistorian/the-great-blizzard-of-1888-americas-greatest-snow-disaster.html

I still think that we have a chance to see a 40-50” snowstorm event somewhere between NYC and Boston in the coming years.

And this may help to compensate for #2 also. But I know that there are extended snow cover fans out there that may not feel that way. I am more about snowstorm intensity and quality than how long it remains on the ground. https://www.sciencedaily.com/releases/2019/01/190124115353.htm Even though climate change is expected to reduce the total amount of U.S. snowfall this century, it's unlikely to significantly rein in the most powerful nor'easters that pummel the East Coast, new research indicates.

Yeah, it really gets back to the competing influences discussion that we had during the fall. The record +PMM was associated with the more Niño-like pattern so far this winter. But now that the PMM is quickly cooling, the models are showing a transition to a more Niña-like pattern. I mentioned this the other day. Now this new tweet is picking up on the idea. It shows how quickly the SST have cooled west of Central America. I posted for the SST chart not for references to any specific analog year.

Yeah, it’s a very well identified pattern. https://www.climate.gov/news-features/blogs/beyond-data/climate-change-rule-thumb-cold-things-warming-faster-warm-things Colder places are warming faster than warmer places Colder seasons are warming faster than warmer seasons Colder times of day are warming more than warmer times of day

Climate Central compiled all the charts. It’s through the winter of 2019. So the record warmth last winter wasn’t included. https://www.climatecentral.org/gallery/graphics/winter-warming-local-average-winter-temperature-2019

Mild pattern continuing on the 12z EPS through the next week of so. This is what happens when mild Pacific air gets stuck under a south based block. The latest weeklies have the retrogression of the ridge back to the Aleutians with a more Niña--like -PNA by late January.

You know it’s a mild winter pattern when even the mountain areas can’t build much of a snowpack.

It will be interesting to see the new EPS weeklies later. The latest GEFS weeklies have a pretty fast retrogression of the ridge back to the Aleutians by late January. This would allow a more La Niña-like -PNA to emerge by later in January into February. So hopefully we can maximize our snowfall potential after January 10th before a possible shift later on.

Stating that we could see a La Niña-like pattern in February means that the ridge could pull back to the Aleutians and the PNA falls. It doesn’t speak to what type of snowfall opportunities that we will see. There also isn’t much correlation between the strength of the La Niña and this February pattern. For example, 16-17 featured one of the weakest La Ninas during February. But it had near record warmth with a memorable blizzard. February 2011 had a much stronger La Niña with the PNA drop. But it was cooler than 16-17 with less snow. So specific temperatures and snowfall can be quite variable within a February La Niña pattern should it arise this year.

I can still remember how surprised everyone was when the La Niña pattern showed up in February 2011. We could have surpassed 95-96 if that pattern didn’t reverse. That’s why I am always cautious when dealing with La Ninas in February.

It may be that the record off equator North Pacific warmth allowed a more Niño-like pattern to dominate since December. But this off equator North Pacific warm has steadily declined in recent weeks. So it’s possible that a more La Niña-like pattern finally emerges in February.

It will be interesting to see how long we can keep it going. I am not aware of another La Niña that had +PNA for the whole winter. The +1.58 PNA for December was out of place for a La Niña. https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.pna.monthly.b5001.current.ascii.table

Hopefully, the EPS is rushing the flip to La Niña in February. Forecasts past week 2 have lower skill. Sometimes week 3 and beyond just defaults to a climo type composite for the ENSO at the time.

New 30 year climate normals will be warmer and snowier.

The only thing we can say about the day 10 to 5 EPS corrections is that the Davis Strait blocking is weaker and the +PNA is stronger. New run Old run

When the 510 Arctic thickness line drops down near the Northeast. Usually this time of year it’s a -10 departure or lower. Highs often stay in the 20s with lows in the 10s. Lows below 10 are usually reserved for the strongest Arctic outbreaks. https://www.weather.gov/source/zhu/ZHU_Training_Page/Miscellaneous/Heights_Thicknesses/thickness_temperature.htm The 5,700, 5,400 and 5,100 thickness lines will be shown in solid yellow. A thickness of less than 5,100 is associated with arctic air while a thickness of 5,700 or greater is associated with tropical air.

Yeah, sometimes just cold enough is all we need at the coast for snow with the right storm track and teleconnections. But it’s always nice to have at least some Arctic air nearby to enhance our chances for a higher end event. Even our recent milder snowy Januaries had intervals around storm time with -10 Arctic air available. NYC Jan 18.....-0.9 2018-01-01 19 7 13.0 -20.4 52 0 0.00 0.0 T 2018-01-02 26 13 19.5 -13.8 45 0 0.00 0.0 0 2018-01-03 30 16 23.0 -10.1 42 0 0.00 0.0 T 2018-01-04 29 19 24.0 -9.0 41 0 0.76 9.8 1 Jan 17.....+5.4 2017-01-06 33 25 29.0 -3.8 36 0 0.05 1.2 1 2017-01-07 26 20 23.0 -9.7 42 0 0.32 5.1 T 2017-01-08 25 16 20.5 -12.1 44 0 0.00 0.0 4 2017-01-09 23 14 18.5 -14.0 46 0 0.00 0.0 3 Jan 16....+1.9 2016-01-19 28 16 22.0 -10.3 43 0 0.00 0.0 T 2016-01-20 37 27 32.0 -0.3 33 0 0.00 0.0 T 2016-01-21 36 26 31.0 -1.3 34 0 0.00 0.0 0 2016-01-22 30 21 25.5 -6.9 39 0 0.01 0.2 0 2016-01-23 27 24 25.5 -6.9 39 0 2.31 27.3 6

The EPS is confirming in the week 2 period that the SPV and coldest temperatures will shift over to Eurasia with the SSW. So we just need to work on getting it cold enough for snow with the right storm track. Maybe there could be some Arctic air by later in the month if heights build enough north of Alaska.

Continuation of the mild pattern that began around the solstice. NYC at +5.7 through the first 3 days of January. NYC will remain well above the 33° average for early January. Maybe we can eventually see some upper 20s lows by later next weekend. But the average low is 27°. New York City... Central Park, NY /42 37/41 33/42 31/43 31/40 30/40 29/40......climo 27/38/33 Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 2020-12-21 5.7 2020-12-22 6.5 2020-12-23 5.3 2020-12-24 16.0 2020-12-25 10.2 2020-12-26 -6.5 2020-12-27 -3.8 2020-12-28 8.4 2020-12-29 2.6 2020-12-30 1.8 2020-12-31 8.4 2021-01-01 3.1 2021-01-02 10.2 2021-01-03 2.9

Need to see some lows in the 20s showing up in NYC for more significant snowfall potential. This first week may join the list of years that didn’t fall below 30°. Something closer to the average low of 27° during the 2nd week of the month could allow for snow potential with the right storm track and evolution. Mid 20s lows before or during a storm can signal enough cold air nearby with the right storm details. This is generally what we look for in a mild pattern. ...New York City... Central Park, NY /38 34/44 34/42 34/43 31/43 Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Lowest Min Temperature Jan 1 to Jan 7 Missing Count 1 2007-01-07 38 0 - 1907-01-07 38 0 2 2005-01-07 34 0 3 2021-01-07 33 5 - 1966-01-07 33 0 - 1932-01-07 33 0 - 1889-01-07 33 0 4 2020-01-07 32 0 - 1874-01-07 32 0 5 1950-01-07 31 0 - 1880-01-07 31 0 6 1939-01-07 30 0 - 1913-01-07 30 0 - 1906-01-07 30 0