bluewave

The one constant with models like the EPS weeklies is that they always seem to struggle even more than at other times of the year with long range December forecasts issued before Thanksgiving. It may have something to do with the change up with the seasonal patterns as we we shift gears from November into December. We have seen some very significant model shifts between November 20th and 30th for even just the first week of December. So I don’t start putting to much stock in them until we get closer to the start of December. Some years the Euro monthly for December nailed the December pattern when issued on the 5th. I can’t remember the last time the model had a successful December forecast issued around November 20th. That being said, we have seen some pretty low skill EPS December forecasts issued on or around December 5th.

It was snowman that posted the tweets from Eric and Paul. My comment was that those constructed analog forecasts beyond 15 days are hit or miss. Not sure if Paul keeps verification statistics on them. There have been numerous times he posted them to twitter and we got completely different patterns. But that is par for the course with forecasts beyond 15 days. We know they are a crapshoot but the public may not realize the difference.

Technically you may be right. But at least for the Northeast, any trough in the West can significantly limit how much cold air is available. It will be interesting to see how this winter plays out with all the competing influences.

It’s not necessary to definitively know whether a persistent pattern is permanent or not in order to use it as an effective forecast tool in the present.

Oh I see what you mean. I think a bunch of stuff gets retweeted or agreed with without people fully looking at what they are retweeting or agreeing with.

Those composite analogs on that site are very hit or miss for forecasts beyond 15 days.

Probably won’t make much difference on the sensible weather pattern whether the ONI peaks at strong or super. It may be more important whether the -PDO or Niña-like pattern continues to play the back and forth with the El Niño. A super El Niño can displace the Aleutian low too close to the Western US. But a -PDO El Niño can do the same thing due to the stronger Aleutian ridge NW of Hawaii. So while some may not technically call it an Aleutian low, any troughing in the Western US could produce the same warm outcome for the Northeast.

A stronger Southeast ridge doesn’t mean imminent doom. Outside this board, milder winters with lower heating bills are welcomed. We are in the minority enjoying KU events and really cold winters. But it’s not a good thing long term if you are in the snow plow or ski business.

And there is zero question in my mind that the next time we miss a snowstorm due to a stronger SE ridge you will just chalk it up to bad luck or random chance.

The historic snowfall outcome in March 2018 for places like Long Island was one of the rare benefits of the rapid WPAC warm pool expansion. The record amplitude MJO 6 drove that SSW and March snowfall extravaganza. I would love to see more months like that was the WPAC warms. But they have been in the minority in recent years. https://wcd.copernicus.org/preprints/wcd-2020-17/wcd-2020-17-manuscript-version3.pdf SSW2018 occurred under the favourable conditions of the easterly phase of QBO, La Niña phase of ENSO and followed the MJO phase 6 with the largest amplitude in observational record (from 1974 to 2018) (Barrett, 2019). Barrett (2019) showed that the large-amplitude MJO episode in 2018 affected weather in the north-eastern United States under the conditions of strengthened Rossby wave teleconnections between the tropics and the extratropics. Furthermore, SSW2018 was preceded by a record-breaking meridional eddy heat flux at 100 hPa observed before an SSW since 1958 (see Fig. A1 in Appendix A, also pointed out by Ayarzagüena et al., (2018)).

Yeah, this has been the case frequently since the super El Niño. Missing a colder storm track in late November isn’t that big a deal since even a colder track is facing more marginal snowfall climo especially near the coast. But during the winter it’s a completely different matter. Missing the colder storm track last December with that last minute Southeast ridge pop up was a complete waste of the 2nd lowest December monthly -AO on record. Then we had the Christmas major flash flooding with that warmer track right after the 40” event in BGM in December 20. People said that it was understandable that December 2015 would be warm anyway since it was a super El Niño. But no other super El Niño produced a +13 winter month and an historic Southeast ridge like that. Plus we had the historic MJO 4-6 for a super El Niño. Then we heard how the February 2018 historic warmth and Southeast ridge was just the La Niña climo for February. But the 500 mb height anomaly in the Northeast was higher than any previous date for the entire winter season. And it was our first 80° reading in February. In 18-19 we heard how the El Niño was just too weak to couple and it was no big deal. But many weaker El Niño’s had no trouble coupling. That Aleutian ridge-Southeast ridge in 18-19 was not normal for even a weak El Niño. The strong Southeast ridge last winter got blamed on the -PDO. But most -PDOs from the earlier era had much weaker Southeast ridge patterns especially when the AO was negative.

The models usually struggle around this time every year trying to get the December pattern correct.

One day is all you need to force a warmer storm track.

In this case it is as the previous runs with less of a Southeast ridge this week didn’t have the La Niña-like forcing near the Maritime Continent. All it takes is for a small amount of forcing in the MJO 4-6 regions for the Southeast ridge to develop. It may not even show on the RMM charts but it’s there on the VP anomaly charts. New runs more Southeast ridge and Maritime Continent forcing Old runs less Maritime continent forcing and Southeast ridge

The NDFD gets NYC down to 33°-34° with widespread 20s in the suburbs.

Maybe we can sneak in a dry Thanksgiving weekend as the Euro and GFS suppress the southern stream low. The CMC still has the storm. But these split flow patterns are very tough for the models.

Tonight looks like it may be the coldest night of the fall so far in NYC. The MOS is down to 34° and some models have 33°. Then the temperatures rebound. What was supposed to be a Thanksgiving cooldown now has highs in the low 50s for NYC which is pretty much close to average.

What we are seeing this week is just more back and forth. The coming -EPO +PNA is more El Niño-like. But the occasional Southeast ridge and warmer storm track next few days is classic La Niña. So my guess is that the El Niño and La Niña influences will continue to compete for influence. This back and forth has been going on since last spring.

All this talk of how strong the El Niño is getting is pretty much moot since it’s still not well coupled with the mid latitude pattern across the North Pacific and North America. The November pattern so far is much closer to the La Niña composite with and Aleutian Ridge and secondary ridge near the Southern Rockies and Plains. The cooler trough near New England is also a November La Niña pattern. The persistent La Niña background state is one reason that November is one of the few months out of the year with cooler departures located near the Northeast. Most other months of the year have been near to record warm.

I have been pointing out how warm the area from the Dateline back to the WPAC has been since last spring. That’s why I though it was unlikely that this would follow the trajectory of a big east based event like 97-98. So now we have +30C near the Dateline and around the Maritime Continent. That’s why we are seeing the forcing back and forth between those regions right now.

I would say the fall pattern has been a blend of La Niña and El Niño influences.

https://www.nature.com/articles/s41558-023-01801-6 Understanding the recent increase in multiyear La Niñas Abstract Five out of six La Niña events since 1998 have lasted two to three years. Why so many long-lasting multiyear La Niña events have emerged recently and whether they will become more common remains unknown. Here we show that ten multiyear La Niña events over the past century had an accelerated trend, with eight of these occurring after 1970. The two types of multiyear La Niña events over this time period followed either a super El Niño or a central Pacific El Niño. We find that multiyear La Niña events differ from single-year La Niñas by a prominent onset rate, which is rooted in the western Pacific warming-enhanced zonal advective feedback for the central Pacific multiyear La Niña events type and thermocline feedback for the super El Niño multiyear La Niña events type. The results from large ensemble climate simulations support the observed multiyear La Niña events–western Pacific warming link. More multiyear La Niña events will exacerbate adverse socioeconomic impacts if the western Pacific continues to warm relative to the central

That the power of even a little forcing near MJO 4-6 around 120 E to pump the Southeast ridge. New run Old run

Looks like NYC continues to miss the freezes with the weak CAA and light winds. Thanksgiving should be a nice day for travel with seasonable temperatures. Good that the rain is coming in ahead of the holiday and after.