bluewave

But the strongest forcing remains near phase 2. Notice the big 30C warm pool centered around 60E. So the forcing may slowdown in 2 instead of going 3-4-5 right away. We’ll have to see. But it’s why I believe the EPS weeklies hold the trough in the west after the first week of January.

Yeah, do think we warm up after the first week of January. Very strong forcing near 60E is close to a MJO 2 signal. The composite has a trough in the Western US during an El Niño. That’s why I think the EPS has that general look. Believe the key to getting any SSW to work for us later January into February is what the Pacific does. As we have seen in recent years, we need the Pacific on our side even with near record -AOs like December 22 and at other times. So let’s hope some backloaded El Niño effect can push back against what the Pacific has been doing in recent years.

Decembers when northern suburbs like HPN can’t drop below 20 or the upper 10s have become more common in recent years. Time Series Summary for WESTCHESTER CO AP, NY - Month of Dec Click column heading to sort ascending, click again to sort descending. Rank Year Lowest Min Temperature Missing Count 1 2015 28 0 2 2012 24 0 3 2023 20 8 - 2021 20 1 - 2014 20 1 - 1984 20 0 4 2018 19 1 - 1997 19 8 - 1996 19 8 - 1974 19 0 5 2011 18 0 - 2001 18 0 6 2007 17 0 7 2006 16 0

While El Niño Decembers are typically mild in the Upper Midwest, this one is taking it to a new level. Nearly 10° warmer than the previous warmest Christmas Eve in MSP during the 1957 El Niño. This is more typical of late October or early April.

The record cold in China this month was balanced out by the record warmth at the beginning.

My main memory of December 97 was the surprise high wind warning right before New Years. Some neighbors threw out unsecured loose paneling by the curb after doing a renovation. It was all over the place the next morning with wind gusts over 60 mph.

To complicate matters even more, humans are quickly able to normalize warming conditions. So while there are people who don’t want to believe we are warming, there are others who normalize it so quickly that it doesn’t feel that unusual. That just seems to be human nature since we are very adaptable. So maybe there are some that don’t see the actual stats and would be surprised that anything out of the ordinary is happening. https://yaleclimateconnections.org/2019/04/normalizing-weather-extremes-dulls-concerns-for-warming/ Moore’s study, published in PNAS in February, found people base their perceptions of normal weather patterns on a two- to eight-year span of time – a short timeframe that can distort perceptions of the effects of climate change. “What’s worrying about this is that the constant rate of adjustment, this rate of normalization of two to eight years, that’s pretty quick compared to the rate at which climate change happens,” Moore says. “So the risk is that if you’re forgetting what happened before eight years ago, then you’re never really going to be able to put the weather that you experience into this longer-term context that really describes the overall effects of climate change.” They found people would tweet about unusual weather conditions like extreme heat or cold events, but the more often these events occurred, the fewer the number of people who posted about them, suggesting they had begun to accept them as normal. “What we show is that, if you have unusual temperatures and this is the first you’ve ever experienced it, that generates a big change on Twitter and people are talking about it a lot,” Moore says. “But if you have that same change … two years in a row, then people begin to stop talking about it. And if you have that same change eight years in a row, then people completely stop talking about it. So what that implies is that people’s idea of normal has shifted from what it used to be to this new state that’s defined by what happened two to eight years ago. And so we’re estimating this is kind of what people think of as normal just based on the rates at which they stop tweeting about unusual temperatures when they get them repeatedly year after year.”

The only temperatures that matter for snow are during the day of the event. Blended long range ensemble means will be too smoothed out for the finer storm details. The general pattern will have issues with a fast split flow. Meaning that amplified systems will track further north and pull in warmer air with them. Like we often see with primary lows running to the lakes and the southern stream riding further north. So you could have cooler to normal temperatures before and after the storm but warm to above normal leading to rain or quick changeovers during the storm. Plus with very progressive patterns it’s tough for high pressure to lock in over SE Canada. Often times the highs are exiting the east coast as storms approach from the west. Weaker systems could completely get suppressed in split flow patterns.

The bar in December has been set pretty low with a trace of snow and another top 10 warmest December. So anything better than that will be considered a victory I guess. But still not seeing a pattern yet which will produce a warning level 6”+ NYC snow into early January. Smaller events can always sneak into otherwise challenged patterns for snow.

It’s a combination of several factors. El Niño coupled with warm MJO phases plus the warming climate. Warmer SSTs in the WPAC slow an amplify forcing there. So instead of a vanilla El Niño pattern which has the warm focused in Canada, this is one of the warmest Canadian and Northern Tier Decembers on record. So the El Niño and MJO give us the geographic locations of the warmest anomalies. But the magnitude of the warmth is where the warming climate contributes.

So much mild Pacific air has flooded Canada, that any continental polar will get modified heading south. That’s why I think the long range models will continue to correct warmer as we get closer to the forecast period. Plus storm tracks with the fast split flow will also present challenges.

Meanwhile, North America drops to unchartered territory for low snow cover heading into the holiday period. https://www.star.nesdis.noaa.gov/smcd/emb/snow/HTML/snow_extent_monitor.html

Obviously, the raw ensemble output has gotten better at forecasting the general patterns especially day 1-5 and 6-10. But beyond that range for the general forecasts, I have been using bias correction to adjust the raw output. So this lead to seeing back in late November that the risks to the week 3 and 4 extended forecasts for mid to late December would be warmer than originally modeled which is what happened. The specifics in December flowed from the much warmer than average pattern coupled with the general storm tracks. Split flow patterns with a lack of cold usually don’t produce much snow which is what has happened in December. The current general forecasts going forward are still lacking the ingredients which would lead to much improved snowfall outcomes for various reasons outlined already in this thread. So several challenges still remain. But even if they did begin to show a better general pattern for snowfall which matched past snowier outcomes, we would not expect models to have an accurate forecast for that until we got under 120 hrs. And even then, we don’t get a true idea of specific snowfall outcomes often until under 72 hrs. Some events like January 2016 and 2015 weren’t even modeled well for specific snowfall amounts 24 hrs out. So specific snowfall forecasting is probably one of the most difficult forecast challenges that we face.

We were discussing a nearly 384 hr GFS OP very low skill hypothetical which changes every 6 hours to pass the time since people have been so bummed out about a lack of snow. Just read back a few pages to see the many challenges the actual pattern will have to produce snow. These continuing challenges through December were outlined here starting back in the late fall. So we were outlining changes which would probably need to happen in order for NYC to break its 1 and 2 inch record long losing streaks.

Scouts can be overrated if you ever saw the movie Moneyball. The patterns only appear complex if you are missing the lowest common denominator or underlying reality.

Then you haven’t been following this thread recently since the wave dynamics leading to these patterns have been spoken about repeatedly. Most people on this forum know that a pattern which produces snow is contingent on cold air. We know that the pattern I outlined which produces the benchmark storm track needs cold air for snow.

Complexity is just an excuse for the inability to see the greater underlying repeating patterns throughout nature which includes weather forecasting.

Sometimes it is when the source regions are devoid of cold enough air as was the case on 12–05-20.

It was implied in my post since I just figured everyone realized that it had to be cold enough for that pattern to produce a 6”+ snowstorm in NYC. We get that pattern plenty of times when it is too warm for snow. So it’s necessary but not sufficient if cold air is lacking. Plus there are many times when some aspect of that pattern present when it’s cold enough but lesser amounts of snow occur.

It seems like we need luck these days to get the Pacific to relax. The amped up Pacific Jet in recent years keeps driving troughs into the Western US. The NYC 6”+ snowstorm composite taking in 19 events since the 09-10 winter shows how important it is to get the Pacific on our side. The primary feature necessary has been a strong 500 mb ridge over the Rockies in the West. The secondary feature has been a Greenland block. NYC 6”+ snowstorm composite of the last 19 events since 09-10 Days used: 1/31/2021 03/14/2017 12/26/2010 12/17/2020 02/09/2017 02/13/2014 02/08/2013 11/15/2018 01/22/2016 02/03/2014 01/26/2011 03/22/2018 01/26/2015 01/22/2014 02/25/2010 01/04/2018 03/05/2015 01/03/2014 12/19/2009

With a little luck we can sneak in a better +PNA look like 12z instead of 6z.But we know these long range GFS OP runs always change. I think it will again come down to seeing if we can get at least a transient break from the trough out West. 12z 6z

Great story. I started out with one of those sleds back in the late 70s. Bethpage State Park was the place to go back then. But transitioned to one of the plastic sleds since the older sleds with the metal runners would tip over more. Plus you had to get out of the way pretty quickly with so many people going down the hills at once.

1963 didn’t make the list for NYC but I can check other locations if you want. Number of Consecutive Days Snowfall < 2 for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Run Length Dates Period of record: 1869-01-01 to 2023-12-21 1 691 2022-01-30 through 2023-12-21 2 685 1972-02-24 through 1974-01-08 3 521 1918-04-13 through 1919-09-15 4 416 1912-12-25 through 1914-02-13 5 406 1997-02-09 through 1998-03-21 6 386 1991-02-27 through 1992-03-18 - 386 1954-01-12 through 1955-02-01 8 385 1931-11-28 through 1932-12-16 9 377 1971-01-25 through 1972-02-05 10 366 2006-02-13 through 2007-02-13

We just exceeded any of the previous snow droughts with under 2 inches from 80s and late 90s. So Pacific has never been this hostile before. Hopefully, we can break this streak before the end of January. Number of Consecutive Days Snowfall < 2 for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Rank Run Length Dates Period of record: 1963-09-05 to 2023-12-21 1 676 2022-02-14 through 2023-12-21 2 631 1997-04-02 through 1998-12-23 3 358 1972-02-24 through 1973-02-15 4 355 1985-02-07 through 1986-01-27 5 348 1986-02-12 through 1987-01-25 6 342 2007-03-17 through 2008-02-21 7 339 2019-02-13 through 2020-01-17 - 339 2000-01-26 through 2000-12-29 - 339 1988-01-09 through 1988-12-12 8 333 2011-02-22 through 2012-01-20

The record warm pattern in Canada got started last May. The record SSTs in the WPAC generated the forcing which lead to historic ridge. Similar pattern to this December.