bluewave

Same situation as we have seen in recent years with the coldest departures going to our west or south. The delayed freeze-up on Hudson Bay and strong blocking there is keeping nearby Canada very mild. You can see the milder temperatures relative to the means working down into Northern Maine.

Yeah, this would have been a colder than average December in earlier decades since the average is close to 40° these days.

The record warm up near the end of the month dropped the monthly average departure to -0.5. EWR….-0.1 NYC….-1.2 JFK…..+0.9 LGA…-1.0 HPN….-0.3 BDR…..-1.3 ISP…..-0.6 AVG….-0.5

Happy New Year everyone. This was probably the most lightning we have ever seen to ring in the New Year. Very impressive light show here.

This was the lowest anomaly we have ever seen this time of year. The EPS weeklies missed this January pattern from back on December 11th. It had lower heights near Hudson Bay and Greenland and not the very strong blocking we have now. Almost looks like the original runs were defaulting to a coupled look with the strong SPV over Canada. Also notice the long range EPS continuing to show too strong a -EPO with lower heights near Alaska than originally forecast. Also a stronger Pacific Jet lowering heights near that region. https://nsidc.org/sea-ice-today/analyses/sluggish-freeze-warming-north https://sites.google.com/view/arctic-sea-ice/home/nsidc-arctic New forecast EPS forecast from December 11th

13-14 was more centered over the Midwest. 93-94 was one of the last times that Canada was able to load with so much Arctic air. Our best Arctic outbreak around NYC since 94 was during one of our warmest winters in 15-16 on Valentines Day. The key was the solid blocking north of Alaska. So NYC was able to go below 0° which it couldn’t pull off in the much colder 13-14 and 14-15 winters.

The Arctic outbreak in early January looks similar to other ones we have seen during the 2020s. The coldest departures relative to the means go to our west and south. Nearby Canada is still warmer than average with the delayed freeze- up around Hudson Bay. https://sites.google.com/view/arctic-sea-ice/home/nsidc-arctic

We are in track for the greatest AO volatility from October into January with possibly the first +4 October daily reading followed by -4 in January. https://ftp.cpc.ncep.noaa.gov/cwlinks/norm.daily.ao.index.b500101.current.ascii

This could be one of our strongest January -AO patterns without a SSW .So maybe the delayed freeze-up around Hudson Bay is giving us an asssit. A very impressive bottom up rather than top down process.

The 7 station December average is currently at -0.9 which will be a little smaller after the 50° warmth today is factored in. EWR…-0.5 NYC….-1.3 JFK…..+0.6 LGA….-1.6 HPN….-0.8 BDR….-1.6 ISP…..-0.9 AVG….-0.9

With the forcing in multiple location on the VP anomalies charts, the early to mid January forecast isn’t the canonical MJO 8-2 where the coldest temperatures are usually found in the Northeast. This time the coldest temperatures will be displaced further to the south and west. Could also be related to the record low sea ice around Hudson Bay with the warmth there.

This may turn into a game of how much spacing we get between the individual shortwaves with so many systems in the fast Northern Stream flow and strong 50/50 low.

Even slightly colder Decembers like this one are still close to 40° around NYC since 2011. Monthly Mean Avg Temperature for LAGUARDIA AIRPORT, NY Click column heading to sort ascending, click again to sort descending. Mean 41.4 41.4 2024 38.6 38.6 2023 44.3 44.3 2022 38.7 38.7 2021 45.0 45.0 2020 40.9 40.9 2019 38.9 38.9 2018 40.5 40.5 2017 36.2 36.2 2016 40.3 40.3 2015 50.8 50.8 2014 40.6 40.6 2013 38.2 38.2 2012 42.7 42.7 2011 43.3 43.3

When you read the study they recently published they only mention some improvement day 3-5 over the NWP models. https://deepmind.google/discover/blog/gencast-predicts-weather-and-the-risks-of-extreme-conditions-with-sota-accuracy/ https://www.nature.com/articles/s41586-024-08252-9 The largest improvements of GenCast are often at shorter lead times up to around 3–5 days,

Boxing Day 2010 was the last time we saw a heavy snowstorm after December 20th. Part of the issue is that the 2nd half of December has been warming faster than the 1st half. The other challenge has been the lack of solid benchmark storm tracks this time of year. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending 12-21 ro 12-31 snowfall 2024-12-31 2.8 2 2023-12-31 0.0 0 2022-12-31 T 0 2021-12-31 0.2 0 2020-12-31 0.0 0 2019-12-31 T 0 2018-12-31 T 0 2017-12-31 0.7 0 2016-12-31 T 0 2015-12-31 T 0 2014-12-31 T 0 2013-12-31 T 0 2012-12-31 0.4 0 2011-12-31 0.0 0 2010-12-31 20.0 0 2009-12-31 1.5 0 2008-12-31 0.5 0 2007-12-31 T 0 2006-12-31 0.0 0 2005-12-31 0.4 0 2004-12-31 2.4 0 2003-12-31 0.0 0 2002-12-31 5.0 0 2001-12-31 0.0 0 2000-12-31 12.8 0

The standalone AI models so far aren’t very good. We can remember the runs when they first launched a while back showing the hurricane going into New England. Then the system wound up curving well to the east. The one use of AI that may show some promise is using in a hybrid form where it corrects the NWP model biases.

I think the ultimate responsibility is on the modeling centers like ECMWF and NCEP for making operational model runs available beyond 120 to 168 hrs. We were joking a few months ago how extending the ECMWF OP to 360 hrs would go over. Once a product is out in the public domain there is nothing to stop someone from posting the image. We know that ensembles are the way to go beyond 120hrs to 168hrs and so do organizations like the NWS. Yet the modeling centers continue to run these OP runs out to 360 hrs and 384 hrs. It would be great if the only guidance products made available beyond 168hrs were the ensembles.

The one significant La Niña sign this December has been the much stronger than normal Northern Stream of the Pacific Jet. It lead to the ridge axis getting pushed further east than forecast with warmer temperatures than issued back on December 5th. Plus the dominant storm track through the Great Lakes was also classic La Niña. Very unusual to get such a strong Northern Stream with a +PNA. So even more of a La Niña mismatch December than we have seen on past occasions. Euro monthly forecast Verification

The mid 60s in NJ yesterday turned out to be a top 5 warmest for December 26th to 31st. Time Series Summary for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending…warmest Dec 26th to 31st 1 1984-12-31 71 0 2 1982-12-31 68 0 3 2008-12-31 66 0 4 2024-12-31 65 2 5 1964-12-31 64 0 - 1936-12-31 64 0

We have had a dominant cutter, hugger, and suppression storm for most of the time since February 2022. So it may take some time to get a coastal track closer to the sweet spot for a 4”+ or 6”+ snow near NYC. You can see all 3 models with the windshield wiper effect from run to run the last 3 days. So it may just take some patience for something to click for us. Since there Northern Stream is still so active wave spacing and suppression could initially be an issue for us. I wouldn’t get invested on any individual system until 2-3 sets of models show it under 120 hrs. Plus we could always get a system that tracks too far north across the area and brings mixing issues near the coast if the vort ejecting from the West kicks up a transient ridge ahead of it.

The only thing I lean on is what I think the actual pattern will be. But colder patterns have been few and far between over the last decade. So it may seem to you that me reporting this is a bias. But it’s the actual pattern which has been biased warm. When we have had really cold patterns over this interval I was there.

That isn’t correct. I had a back and forth temperature pattern for this month. The only warm up that I highlighted back in late November and early December was the 55°+ day which occurred on the 17th. All I said about the cooldown before Christmas was that it probably wouldn’t be a cold as the one in 2022 for NYC which was correct. But commented on the similar timing both years. Then I was discussing that the warm up this week would probably wait until closer to the New Year. I said probably over 50° but it came in a little earlier and was around 10° warmer in spots. My guess for this month for the 7 station average was -1 to +1. So my forecast for this month wasn’t that warm compared to what the final will be. The reason you think I may lean too warm is related to the fact that most of the time we have actually been much warmer than normal. Since portions of the northeast have had over 50 top 10 warmest months since 2010 to only 1 top 10 coldest month. So it’s the actual pattern which has been warm and I have just been describing what has been happening.

We can see a back and forth shift from run to run with set ups like this. The good news is that the AO blocking has corrected much stronger in recent days. So it will probably take time for the Pacific flow to back off enough for a nice East Coast snowstorm. But we often have to be patient in situations like this since it’s hard to tell which shortwave will be the first to establish the favorable storm track.

The ridge today was a little weaker over Oregon with the fast Pacific flow lowering heights from yesterday for the storm on the 6th. So the storm ends up further south today under the block. We probably have to be patient with patterns like this since it can take time for the Pacific and Atlantic get in sync for a nice east coast storm. New run Old run

It may take some time for the fast Northern Stream to back off a bit. We saw it was a big player in December. The EPS is just a few degrees too far east with the systems. So it has an active storm track into British Columbia and just off the East Coast. Slow the Pacific flow just a bit and we will be in business here.