bluewave

The only -EPO drop of the whole winter so far was a few days before the the snowstorm. So the +PNA and -AO couldn’t get the job done without the -EPO assist. This was when the strong block popped up over the pole. ftp://ftp.cdc.noaa.gov/Public/map/teleconnections/epo.reanalysis.t10trunc.1948-present.txt 2020 12 01 57.33 2020 12 02 -20.52 2020 12 03 1.92 2020 12 04 -3.55 2020 12 05 18.98 2020 12 06 113.53 2020 12 07 160.49 2020 12 08 91.29 2020 12 09 24.46 2020 12 10 -40.49 2020 12 11 -98.53 2020 12 12 -90.08 2020 12 13 -32.48 2020 12 14 -11.99 2020 12 15 48.80 2020 12 16 122.15 2020 12 17 153.25 2020 12 18 199.37 2020 12 19 250.26 2020 12 20 239.82 2020 12 21 120.24 2020 12 22 70.85 2020 12 23 58.12 2020 12 24 69.31 2020 12 25 92.27 2020 12 26 68.14 2020 12 27 3.10 2020 12 28 -1.63 2020 12 29 11.33 2020 12 30 61.32 2020 12 31 60.59 2021 01 01 127.22 2021 01 02 264.17 2021 01 03 296.05 2021 01 04 248.51 2021 01 05 260.79 2021 01 06 249.45 2021 01 07 137.72

The cold 13-14 and 14-15 winters seem like a long time ago. It’s like the super El Niño in 15-16 hit the warm reset button. We knew something extreme was going on when December 2015 went +13.3.

This repeating model error has been so frequent in recent years, that the Upper Plains is one of the few spots on the planet that will see a slight decline in the new 30 year climate normals. Time after time, the coldest temperature departures have been dropping to our west. I guess the Pacific Jet is just too difficult for the models to handle long range.

It looks like the coldest temperatures by later in the month will drop to our west again. Notice how much weaker the Pacific blocking is along the West Coast of North America than originally forecast. The extreme Pacific Jet that brought record low pressure to the Aleutians just won’t relax. New run Old run

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.