bluewave

I posted the Pacific Jet correcting much stronger in the above post. The JMA site has the MJO jet composites. Just select the options for 200mb zonal wind anomaly. The jet increases across large swaths of the North Pacific when forcing is in the 4-7 regions. We are currently near a 4 composite for December with the jet pushing through the -EPO block this weekend. https://ds.data.jma.go.jp/tcc/tcc/products/clisys/mjo/composite.html

Yeah, we were discussing the issues with the much faster Pacific Jet and inability to sustain -EPO patterns. All the guidance has been underestimating this influence beyond a week out. This recent +AAM driven Pacific blocking pattern reverses fairy quickly. The forcing near the Maritime Continent accelerates the Pacific Jet, weakens the -EPO, and leads to a Southeast Ridge. New run faster Pacific Jet weakening -EPO block and leading to Southeast Ridge several days later Old run

Yeah, the nearly doubling of the Indio-Pacific warm pool has become a major climate driver especially for us in the East. https://www.climate.gov/news-features/featured-images/warm-pool-indo-pacific-ocean-has-almost-doubled-size-changing-global

The record warmth continues to defy expectations based on past El Niño events with the warming starting earlier and now continuing later.

I don’t devote separate threads to my discussions and forecasts. They are included in the NYC Metro and annual ENSO threads here. My sea ice and global temperature discussions are in the CC forum.

We are currently ENSO cold neutral as the La Niña is taking time to develop. But if we do follow the typical La Niña pattern, then 3 inches in December is the cutoff. Below that and NYC will have a below average snowfall season. December 2001 and 1996 were cold neutral and only had a T with below average seasons. The one early snowfall indicator which has worked for every La Niña winter in NYC going back to the 95-96 has been the December La Niña snowfall. Years with 3 or more inches December have gone on to above normal seasonal snowfall. Every December with under 3” has had a below average snowfall season. This is why December is so important with La Ninas around NYC. 22-23….Dec snow…..T……season….2.3 21-22…..Dec snow….0.2…season…..17.9 20-21…..Dec snow….10.5…season…38.6 17-18……Dec snow….7.7…..season…40.9 16-17…….Dec snow…3.2…..season…30.2 11-12…….Dec snow….0…….season….7.4 10-11…….Dec snow….20.1….season….61.9 08-09…..Dec snow….6.0……season….27.6 07-08…..Dec snow…..2.9…..season….11.9 05-06…..Dec snow…..9.7…….season…40.0 00-01……Dec snow….13.4……season….35.0 99-00…..Dec snow…..T……….season….16.3 98-99…..Dec snow…..2.0……..season….12.7 95-96…..Dec snow…..11.5……..season….75.6

The north-south bridges like the Throggs Neck will probably have more impressive crosswinds with the westerly flow.

I think that the winds will be the biggest story tomorrow. These will be some of the steepest low level lapse rates we have seen this time of year. Models usually underestimate wind gusts in these situations. So there could be gusts in the 50-60 mph range.

It’s no surprise the models have adjusted warmer going forward. The WPAC warm pool along the equator was the warmest for November at just over a +29.05°C. Forcing in these areas leads to a more pronounced Southeast Ridge.

Certain types of patterns have become more common over the last decade. So it’s not cherry picking pointing out the obvious. The bias being discussed involves the models.

That was our last month with an average temperature below freezing and above normal snowfall thanks to the MJO 8.

Yeah, it could be related to the warmest departures setting up just to the west of the main ridge axis near Minnesota and the Dakotas where the cold bias was. It’s also possible the drought enhanced the radiational cooling over the Northeast with so much high pressure and light winds. So the Euro could have missed that. Most other times over the years we had a cold bias on those charts when the ridge was in the East with higher dew points.

You missed the broader context of my analysis which is why you incorrectly used the term cherry pick.

It was probably due to the ridge axis setting up over the Upper Midwest and Canada. So the models underestimated the temperatures under the strongest ridging. The ridge most other times has been located further east. So this has been where the typical cold bias has been. Unfortunately, DTN only posts the 90 day averages. So we don’t get to see the biases for specific patterns which produce a ridge in the East. Pattern dependent biases is the next level but they may not have the computer tech to pull off such specific data. I have noticed when the ridge sets up over the East this is when the cold biases occur. Shift it back to the upper Midwest and this is where the cold biases occur. But the northeast when averaged out over the last 10 years shows a consistent longer range bias beyond the what the shorter 90 day average shows. Most recent 10 year 500 mb height anomaly stronger in East which is a reversal from previous 10 year period

This is one of the reasons that the last 9 winters here have had an average temperature the equivalent of what Northern Virginia used to have from 1981-2010.

If you go back in these various threads including the ones in the NYC Metro forum you will see me positing model biases all the time. This is how I have been able to identity where the potential errors were to the forecasts going back years in these threads. I apply these corrections manually. If you can train the models with AI to adjust for these biases, then my guess is that the forecasts for weeks 2 and 3 would greatly improve. This could also lead to better seasonal forecasts beyond the 1 month range.

The ridge in the East has been one of the most under-forecast features beyond 7 days going back to December 2015 which leads to warmer temperatures than originally forecast. My guess is that this has something to do with the models underestimating long range convection near the Maritime Continent. Since forcing in that region leads to higher 500mb heights and temperatures in the East. 11-15 EPS forecast significantly underestimated Maritime Continent forcing Verification much stronger forcing

This has been the repeating theme over the last 9 winters. Longer range models underestimate the forcing in the MJO 4-7 regions. So they start out too cold for our area and then shift warmer the closer we get to the forecast period. New run stronger forcing near the Maritime Continent Old run was underestimating the forcing there

Your colder example is the exception to the rule which will eventually happen from time to time. But most of the time the models adjust warmer as we get closer we get to the forecast period. The colder pattern than originally forecast around the start of December was the result of the models adjusting to the +AAM rise. But at the same time they underestimated the forcing currently in MJO 4 going over +2.00. Stronger forcing in that part of the world accelerates the Pacific Jet and weakens the -EPO. So you had one event strengthening the -EPO and another weakening it. The height falls showing up near Alaska around the 7th with a faster jet than forecast weren’t there previously when the models were underestimating the forcing near the Maritime Continent. This process lead to the quick change in the week 2 forecast to much warmer than previous runs. This is why I was mention earlier back in this thread that the EPS was probably underestimating the Pacific Jet.

This has been one of the bigger reversals from cold to warm that we have seen from the EPS weeklies during this time of the year. https://charts.ecmwf.int/products/extended-anomaly-2t?base_time=202412020000&projection=opencharts_north_america&valid_time=202412160000 Dec 9-16 new run Dec 9-16 old run

Our last +4 east based El Niño during the winter was 97-98. https://www.cpc.ncep.noaa.gov/data/indices/ersst5.nino.mth.91-20.ascii

A recent paper is trying to figure out why the EPAC hasn’t warmed like the rest of the Pacific and whether it will continue. It will be interesting to see if the record EPAC WWB and warming in the spring of 2023 was the beginning of a shift. Plus we just had the near record EPAC WWB back in November with the +AAM. It’s also possible that the big jump in global temperatures which wasn’t forecast last few years is somehow related.

We will probably need to see more Nino 1+2 warming in order to try and shift the Pacific cold phase. But even if we do a potential warm phase will still have to compete with the WPAC warm pool near the equator. In the age of marine heatwaves any cold pool east of Japan would pale in comparison to the marine heatwaves across other parts of the Pacific which would be different from our last +PDO era. Another wild card could be that we could actually see an east based El Niño like 97-98 should 1+2 really take off. But the actual 500 mb pattern could be different due to a stronger WPAC warm pool.

My guess is that will need a solid MJO 8 in January like in 2022 to see more than a brief 10 day window of cold.

January 2022 was the last time my area had a real winter month with the average temperature below freezing and heavy snows.