bluewave

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.

The breaks of sun allowed Central Park to jump up to 61°.

That’s why we get such big variance between the collection of OP Euro, GFS, and CMC runs beyond 120 hrs. The ensemble means try to smooth out the spacing and amplitudes of each individual shortwaves. So ensemble means probably are good starting point for us.

NAO and AO volatility continue to be the big story since the summer. Big swings both using 500mb anomalies and the raw teleconnection indices. Very challenging to do a long range forecast of these indices with such record swings. We have seen unprecedented volatility since 2009-2010. New EPS run first week of January Old run

This rapid increase in AO blocking over the last 10 days of runs may be getting and assist from the record warmth around Hudson Bay with the lowest ice there on record for this time of year. New EPS run first week of January Old run

Low 60s today from CNJ to Newark with 50s most other spots.

It’s patterns like this that make us want to see OP runs only be made available through 120-168 hrs. Everything beyond that point should just be ensemble means. People posting these individual long range OP snowfall charts on social media will actually cause issues for the NWS. We saw this several years ago when some long range OP snowfall charts were posted around Philly and the NWS had to issue a statement due to a poster on social media. I think it’s the responsibility of the modeling centers to do this since once a model forecast is in the public domain it’s going to be posted by somebody.

Yeah, it can snow pretty much anytime in January or February regardless of the monthly average temperatures with the right storm track. We got this with the snow near the 80° day in February 2018. Then again multiple times in winters like 16-17 with blizzards the day after 60s record warmth.

Storm track is more important than average temperatures for NYC snowfall in January. Since it can always snow even when it’s warm this time of year with the right storm track with the average temperatures most Januaries.The temperatures only matter on the day of the event along with the storm track. NYC January average temperatures and snowfall last 10 years 2024….37.0°….2.3” 2023….43.5°…T 2022….30.3°…15.3” 2021….34.8°…2.1” 2020….39.1°…2.3” 2019….32.5°…1.1” 2018….31.7°….11.2” 2017….38.0°…7.9” 2016….34.5°…27.9” 2015….29.9°…16.9”

The OP and ensemble mean are different sides of the same coin. One is overamped on the northern stream and the other is a weaker system moving through in the fast flow. Hopefully, we can slow the Northern Stream influence enough to allow us to maximize the window of opportunity we get this month.

From JFK to ISP and Shirley it’s in the low 50s.

The highs already beat guidance today as we are low 50s around NYC and Long Island instead of mid 40s.

Maybe if you lose the primary running through the lakes and turn it into more of a SWFE event. But that would risk a scenario like the CMC has a weaker wave north and the southern stream getting suppressed. Too dominant a northern stream and you get a 1-3 or 2-4 then with mixing issues after.

Just goes to show how important storm tracks are. The December before that one was the 2nd coldest on record at 25.9° in NYC. But the Northern Stream was so overpowering that NYC only finished with 1.4” of snow as the big snowfall event missed to our south. December 1990 was the 10th warmest on record at 42.6°. But NYC was able to finish the month with 7.2” due to a favorable storm track on one day even in a sea of warm.

The last back to back below average temperature winter months were December 2017 into January 2018. NYC Feb 24…+4.2 Jan 24..+3.3 Dec 23..+5.5 …………..+4.3 Feb 23…+5.2 Jan 23…+9.8 Dec 22…-0.6 …………..+4.8 Feb 22….+1.4 Jan 22….-3.2 Dec 21….+4.7 ……………..+1.0 Feb 21….-1.7 Jan 21….+1.1 Dec 20…+1.7 …………..+0.4 Feb 20…+4.8 Jan 20….+6.5 Dec 19….+0.8 …………….+4.0 Feb 19….+0.9 Jan 19….-0.1 Dec 18…+2.6 …………….+1.1 Feb 18…+6.7 Jan 18….-0.9 Dec 17…..-2.5 …………….+1.1 Feb 17…..+6.3 Jan 17….+5.4 Dec 16….+0.8 …………….+4.2 Feb 16….+2.4 Jan 16….+1.9 Dec 15….+13.3 …………….+5.9

This winter was the strongest lagged La Niña that we have ever seen. Notice how much warmer the global SST state is than all the other La Ninas over the last 30 years. It allowed the RONI to drop well below the actual Nino 3.4s.

Looks like the AAM is forecast to drop as per the CFS forecast as the La Niña moves into the moderate range.

The cold departures will be shrinking to close out the month with 3 days going +10 or higher.

The UHI in Manhattan has been in effect since the 1890s and Queens since the 1930s to 1950s. But it’s just more obvious when we have calm winds. Plenty of strong high pressure this month for radiational cooling.