bluewave

We have been the wettest part of the country.

Close to average next 10 with some milder days and cooler ones mixed in. Then maybe moderating a bit week 2. But the means are falling this time of year anyway. The coolest departures look like they will set up over the SE.

Yeah, the rate of Nino 3.4 warming peaked back in August. This coincided with the actual peak in 1+2 and peak in WWB activity so far. While the WWBs have picked up in October relative to September, there is less of a warm water supply in 1+2 to spread out west like we had in August. So Nino 3.4 SSTs continue around 1.43 even with better WWBs this month. The current lack of a strong oceanic kelvin wave and lower upper ocean heat content is slowing things down relative to what we have seen during past El Niño events.

August was our only decent WWB month. So that’s why we had the steep Nino 3.4 rise. The CP trade wind index for August says it all. We can see the decline in WWBs for September leading to the Nino 3.4 drop in recent weeks. https://www.cpc.ncep.noaa.gov/data/indices/cpac850

October 2009 was the last time the CONUS had a top 5 coldest month. https://www.ncei.noaa.gov/access/monitoring/monthly-report/national/200910#:~:text=The average October temperature of,reinforced unseasonably cold air behind Temperature Highlights - October The average October temperature of 50.8°F was 4.0°F below the 20th Century average and ranked as the 3rdcoolest based on preliminary data. For the nation as a whole, it was the third coolest October on record. The month was marked by an active weather pattern that reinforced unseasonably cold air behind a series of cold fronts. Temperatures were below normal in eight of the nation's nine climate regions, and of the nine, five were much below normal. Only the Southeast climate region had near normal temperatures for October.

The one thing that I would add is that this October is running much warmer than years like 2009 and 1976. October 2009 was actually the 4th coldest for the CONUS on record and 1976 2nd coldest. Same way like this summer was much warmer than 2009 even though both years had great summer blocking patterns.

No problem. Not saying I know for sure what is going to happen. Just not a big fan of this persistent -PDO La Niña background state .I don’t mind it as much when it’s uncoupled like Jan 22 and Dec 20 to Jan 21. But it’s very tricky to try and figure out ahead of time when it’s going to couple or not. Plus we have these interference patterns which can arise when the ENSO and PDO our out of phase. Also these troughs seem to find a way to sneak in out West during recent years.

The relevant part is how even a weak -PDO with an El Nino can put a trough in the West like 72-73.

The issue with WWBs coming on so late is that any oceanic kelvin wave generated would also be too late to move the El Niño much more past what we have already seen. Most fall oceanic kelvin waves that have sharp El Niño warming get generated by WWBs during late summer into September. This year we had stronger trades and an absence of WWBs. So any potential kelvin wave warming would come after the El Niño has already peaked.

Tug of war between El Niño in the tropics and -PDO in subtropics or extratropical regions.

It doesn’t have to if the -PDO is coupled well. We can remember back in the 18-19 El Niño that struggled to couple how the well coupled -0.42 -PDO was enough to place the trough in the West. But each winter is different so we’ll just have to see how things play out. Plenty of variables and combinations to factor in.

MJO 7 region forcing west of the Dateline like we are currently getting can mimic a MJO 5 when the PDO is very negative.

Hopefully, the MJO 4-6 doesn’t rebound as much as we saw with the last record +IOD back in 19-20. That event only suppressed convection near the Maritime Continent into early December. So IODs are mainly a fall event and the influence wanes by the winter. Once the IOD dropped under +1 in December 2019, the Maritime continent convection returned.

OCT…….6-8…..0.49

The only real winters in the 90s were 93-94 and 95-96.

Crazy how Sandy was exactly a year later.

Those were the glory days for the Euro when it believe it was the first model to show an unusually early season snowstorm in the Northeast. Even though it was too snowy at the immediate coast, it was still the greatest early season snowstorm on record.

This would actually be a good trend if we got it in the winter. Much stronger blocking to the north preventing the primary from cutting to the Lakes. So we get a forced redevelopment to our south. If this was the winter, we would be hoping later runs don’t correct north. New run Old run

With the current upper ocean heat value just under +1, we continue to see Nino 3.4 pulling back from the highs in late September. The current daily value of +1.44 is well below the Euro monthly average forecast of 2.03 for October. So this could be one of the greatest Euro forecast misses issued in September for October. https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/?enso_tab=enso-sst_table ECMWF 2.03

Yeah, the NPAC firehose jet is knocking down the +PNA ridge too quickly so primary runs to the lakes. The STJ can’t completely take over like we would want to see. There has been quite a bit of this type of storm track behavior in recent years.

The cold coming up doesn’t look too impressive for October. But it will certainly feel that way due to the 80s to start the month. So it’s all relative.

The Euro is already running too warm for October. It has a monthly average of 2.03. As of 10-07 Nino 3.4 is +1.52. So the dailies would have to increase to at least above +2.25 in the coming weeks for that monthly average number to verify. But there are no big WWBs in the forecast plus the OHC is currently to low to support such a steep rise. https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/?enso_tab=enso-sst_table ECMWF 2.03

October is turning out to be a blend of El Niño and La Niña 500 mb composites. So this is what we get with a borderline strong El Niño around +1.5 and a -PDO near record low levels. The ridge NW of Hawaii and strong low south of Alaska in October is classic La Niña. But the ridge over NW Canada is more El Niño. A La Niña pattern in October has a +EPO and an El Niño -EPO. So we can see the back and forth with the EPO in the forecast. https://ds.data.jma.go.jp/tcc/tcc/products/clisys/enso_statistics/index.html October El Niño 500 mb composite October La Niña 500 mb composite Forecast has elements of both composites

Sure. This article has the charts and a link to the paper. https://news.climate.columbia.edu/2019/06/24/pacific-ocean-cold-tongue/

While the oceans have been steadily warming as a whole, it has been uneven. So some areas such as the IO into WPAC and NW Atlantic with slowing AMO have been warming more rapidly. Plus we have the mystery of the EPAC cold tongue defying the global trends like the famous cold pool south of Greenland. But even though the slowing AMOC has been implicated in that cold pool, the EPAC cold tongue remains a mystery. Below is an excerpt from a recently published article in New Scientistmagazine: “For years, climate models have predicted that as greenhouse gas emissions rise, ocean waters will warm. For the most part, they have been correct. Yet in a patch of the Pacific Ocean, the opposite is happening. Stretching west from the coast of Ecuador for thousands of kilometres lies a tentacle of water that has been cooling for the past 30 years. Why is this swathe of the eastern Pacific defying our predictions? Welcome to the mystery of the cold tongue. This isn’t just an academic puzzle. Pedro DiNezio at the University of Colorado Boulder calls it ‘the most important unanswered question in climate science’. The trouble is that not knowing why this cooling is happening means we also don’t know when it will stop, or whether it will suddenly flip over into warming. This has global implications.” “SOEST scientists are on the forefront of researching this critical question in climate science and related topics–for example, tropical Pacific climate change in general, El Niño, and Pacific decadal variability,” said Malte Stuecker, assistant professor in the SOESTDepartment of Oceanography and International Pacific Research Center, who was also featured for the New Scientist article. “For how long the cooling in the eastern Pacific persists and when exactly it will flip to warming will have big implications for regional climate predictions and adaptation efforts – including for Hawaiʻi.” To make progress on the cold tongue mystery, Stuecker co-leads an international coordinated working group under the World Climate Research Programme called TROPICS.