bluewave

This will probably be the first time in the last few years that a week 2 forecast trended colder instead of warmer. New run Old run

It’s possible that we are seeing the early stages of some type of 500 mb regime shift in the North Pacific. The ridge today in the Bering Sea has exceeded a +500 meter anomaly which is one of the strongest on record for this time of year. SST indices like the PDO are usually lagging indicators after the 500mb pattern gets stuck in place for a long enough period of time. For the 2020s so far the North Pacific Ridge has been anchored to the south of the Aleutians. So if the pattern can persist past the first week of December it’s possible that something significant shifted with this +AAM rise and WWB which caused the Nino 1+2s to warm off of South America. Near record 500 MB heights today Bering Sea 2020s mean ridge south of Aleutians

Would be an interesting question since the atmospheric 500 mb state now is more El Niño +PDO than La Niña with the high AAM pattern.

Even NOAA isn’t sure of what’s going on as this WWB and ENSO warming wasn’t forecast by any of the models along with the sudden jump in global temperatures starting back in 2023. https://www.newscientist.com/article/2452742-the-mystery-of-the-missing-la-nina-continues-and-we-dont-know-why/#:~:text=While sea surface temperatures in,by the end of November. An expected shift to cool La Niña conditions in the Pacific Ocean has been delayed again. Forecasters now project only a weak event to emerge by the end of November, which is likely to limit the cooling influence of the climate pattern on global average temperatures. “I do not know why it has slowed down,” says Michelle L’Heureux at the US National Oceanic and Atmospheric Administration (NOAA). “If someone did, we might have been able to predict it.”

If we can hold that day 11 snapshot, then it would be a blend of December 2017 and 2009. It will be interesting to see how long we can sustain that pattern since the MJO indicator in October that I discussed was going for a mismatch in December like we saw in 2020, 2017, and 2010. But since this La Niña was weaker than those years it was uncertain how well it would work. The WWB and AAM rise and ENSO warming we just saw may have been related to the very amplified MJO 5 wave that we saw in October. Still too early to tell how long that day 10 pattern lasts but we should know one way or another by the first week of December. We’ll know at that point if the pattern has staying power or it switches back to something more Niña-like after week 1.

Very compact circulation on HRRR with a sting jet-like feature near the LI South Shore.

Yeah, the challenge is that many of these AMOC forecasts are based on models with proxies and not direct measurements. This recent study on the Florida current is actually measured and is maintaining its strength. Other studies on the cold blob in the North Atlantic suggest that it may be a function of more persistent +NAO patterns at times. They still don’t know if it’s caused by glacier melt with fresh water. It’s possible that it could be a function of both but how much each contributes is an unknown. When we look at some of the AMOC slowdown forecasts they resemble a +NAO pattern. Notice how the models show the record SSTs and warmth near the NW Atlantic and New England while the NAO area expands and cools. A more amplified version of what we have seen in recent years.

Sometimes those composites work and other times the JMA are more reliable. Many of the MeteoNetwork composites are lower sample size. I translated the site to show the color codes and the degree of reliability. MJO Tables - MeteoNetwork Medium-high reliability Medium-low reliability Low reliability Plotting not available due to lack of data I like the JMA since each composite is based on a big sample size from 60 to 100 dates. Sample size can often be an issue with MJO composites so you need to see which work better in real time and then try to extrapolate out where the MJO is going and whether it’s having a strong enough effect. This current pattern forecast for late November is more of a +AAM with blocking near the Aleutians and Baffin Island. So the MJO may still be running in the background but not dominating the pattern. We’ll have to wait until early December to determine whether the +AAM dominates or we get a warmer MJO 5-7 influence. Another possibility would be an odd combination of both almost like wave interference. https://ds.data.jma.go.jp/tcc/tcc/products/clisys/mjo/composite.html High AAM pattern for late November

You can see the EPS weeklies showing mixed influences between Nino-like and Nina-like elements. We will probably need at least another 10 days to know which becomes more dominant. Another possibility is that we get some type of interference pattern between the two but still too earky to know. https://charts.ecmwf.int/products/extended-anomaly-z500?base_time=202411190000&projection=opencharts_global&valid_time=202412020000

Another thing to watch may be a sting jet-like feature just south of the low.

This is probably the first time we had such an impressive November Nino temperature rise following a borderline super El Niño SSTs like last winter.

This looks like one of the strongest storm systems we have seen in the East this year near -4SD.

You can see the battle unfolding from run to run between how long to linger this current more Nino-like regime and how fast to bring back a more Niña-like background pattern.

The Gulf of Maine is near the warmest on record for this time of year. https://mco.umaine.edu/climate/gom_sst/

GMRI tracks this part of the Atlantic which has consistently been near the warmest on record in recent years. https://gmri.org/stories/gulf-of-maine-warming-update-summer-2024/