bluewave

A very Merry Christmas and Happy Hanukkah to everyone. This had to be the thickest fog that I have ever driven in during Christmas. It was an interesting ride home over the hills here in Southern CT. I am more accustomed to driving in dense fog on flat surfaces like the Ocean Parkway back on Long Island. But the up and down on hills in the dense fog was pretty wild.

Yeah, I remember. We should develop a custom set of indices based more on 500 mb composites. Several times the CPC raw indices don’t do pattern justice. I know most on here consider it a -PNA when there is a trough in the West even with a ridge over the top in Canada which computes as a +PNA on the CPC site. This was the case last January. I would also develop a custom Southeast ridge index.

I am not too concerned about the next few weeks since this season like most El Niños will be judged on what happens after January 15th.

Most of us will call it a -PNA as long as there is a trough the Western US. But it’s possible we may get a technically +PNA with a ridge over the top in portions of Canada. I have seen many times the official CPC site call it a +PNA when we had a trough in the West due to ridging in Canada.

One of my favorite Irish singers who also left us way too soon. Merry Christmas to everyone.

It has been easier for Newark to reach 50° on Christmas since the super El Niño in 15 than reach 90° on July 4th. Data for December 25 - NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Date Max Temperature Min Temperature Precipitation Snowfall Snow Depth 2022-12-25 30 14 0.00 0.0 0 2021-12-25 55 38 0.16 0.0 0 2020-12-25 62 28 0.66 0.0 0 2019-12-25 48 27 0.00 0.0 0 2018-12-25 42 29 0.00 0.0 0 2017-12-25 38 28 0.20 0.1 0 2016-12-25 52 34 0.00 0.0 0 2015-12-25 63 54 0.03 0.0 0 Data for July 4 - NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Date Max Temperature Min Temperature Precipitation Snowfall Snow Depth 2023-07-04 83 74 1.19 0.0 0 2022-07-04 91 64 0.00 0.0 0 2021-07-04 84 64 0.00 0.0 0 2020-07-04 87 70 T 0.0 0 2019-07-04 89 74 0.00 0.0 0 2018-07-04 89 76 T 0.0 0 2017-07-04 88 71 T 0.0 0 2016-07-04 84 62 0.46 0.0 0 2015-07-04 79 70 T 0.0 0

Heavy thunderstorms and low 40s later in the morning to heavy snow and 5-10” in the evening near the coast. CT STAMFORD 5 N COOP 10.0 NY BRONX COOP 9.9 NY YORKTOWN HEIGHTS 1W COOP 9.2 NY DOBBS FERRY-ARDSLEY COOP 9.0 NY OCEANSIDE COOP 8.0 NY ISLIP-LI MACARTHUR AP WBAN 8.0 NJ CHARLOTTEBURG RESERVOIR COOP 7.5 NY MINEOLA COOP 7.2 NY LAGUARDIA AIRPORT WBAN 6.3 NJ ESSEX FELLS SERVICE BLDG COOP 6.0 NY SEA CLIFF COOP 6.0 NJ CANOE BROOK COOP 5.7 NJ WANAQUE RAYMOND DAM COOP 5.5 NY JFK INTERNATIONAL AIRPORT WBAN 5.1 NY NY CITY CENTRAL PARK WBAN 5.0 NJ MIDLAND PARK COOP 5.0

What about the rest of North America? https://globalcryospherewatch.org/state_of_cryo/snow/

Alaska is one the few locations in North America that can do OK on snowfall with an overpowering +EPO pattern.

You are doing a fantastic job. Really beautiful display. Even during the colder era, it didn’t snow that much on Christmas. 2002 was our snowiest Christmas in almost 100 years. But it was a real rarity. Data for December 25 - NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Max Temperature Min Temperature Precipitation Snowfall Snow Depth 1909-12-25 38 31 0.34 7.0 M 1902-12-25 34 25 0.72 6.5 M 2002-12-25 37 31 1.30 5.0 M 1883-12-25 31 28 0.38 5.0 M 1904-12-25 27 21 0.16 3.0 M 1969-12-25 29 14 0.25 2.1 0 1975-12-25 33 17 0.17 0.5 T 1935-12-25 30 17 0.05 0.5 T 1879-12-25 40 21 0.32 0.5 M 1976-12-25 36 23 0.06 0.4 0 1966-12-25 32 23 0.05 0.4 7 1924-12-25 36 15 0.04 0.4 T 1962-12-25 35 24 0.10 0.3 T 1974-12-25 40 34 0.19 0.1 0 1926-12-25 43 34 0.09 0.1 T 1919-12-25 27 16 0.01 0.1 2 1892-12-25 24 18 0.01 0.1 M

We have had an active STJ and NPJ split flow dueling all month.

The main difference these days between El Niños and La Ninas in December is the location of the +10 or greater departures. During El Niños the warmest departures are in the north with the +PNA. They shift to the south during the La Ninas with the -PNA. Getting 3 Decembers since 2015 with any section of the US going higher than +10 is pretty extreme. +10 or greater departure months used to be very rare. The +10 at some stations last January in the Northeast was a 4th month which was during a La Niña. A 5th month was the +10 in the Southeast in February 2018. January 2020 which was neutral came close in some locations.

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.