bluewave

We have seen very low skill forecasts issued in late November for December. The EPS weeklies completely missed how warm things got in December 2015 from the November 22nd forecast. So these weekly to monthly and seasonal outlooks can have significant errors.

Better El Niño forcing yes, but we need to lose the coupled -PDO so we don’t end up with a trough near the West caped by a +PNA ridge in Canada. That would drive the downstream ridge over the Northeast which we don’t want. It was what the Euro seasonal was showing. Plus my comment was more to how well the model did with the last non-La Niña winter. Not that this was a copy so far of that year. Outside the Pacific, we have had very impressive blocking on the Atlantic side since June.

Yeah, we would want to see the PDO remain uncoupled if it does stay negative. While the JMA has done OK with recent La Niña winters, it didn’t do very well with the El Niño in 18-19 that couldn’t couple. So it put all its eggs in the Modoki basket which didn’t verify. The well coupled -PDO wound up running the table instead.

It’s a significantly warmer winter temperature version of the 02-03, 09-10, and 14-15, Modoki El Niño forcing west of the Dateline. Even though the PDO is neutral to negative with warmth north of Hawaii, it doesn’t look like the PDO is coupled enough to drive the bus. That strong -EPO +PNA is more +PDO-like. It’s also giving a solid -AO signature. The winter temperatures aren’t nearly as cold as the composite but I am sure that 500 mb look would be better than the last few winters for snowfall. The only colder areas are south of 40N along the East Coast.

One of these winters we may just have to rely on the new warmer 91-20 climate normals. The warmer winter averages could help with a winter that gets close but would have been warm under 81-10 normals. This is how we got a cooler summer in the Northeast this year. The new warmer 91-20 climate normals allowed the Northeast to finish the summer at -0.2. But under the cooler 81-10 climate normals it would have been +0.4.

It goes beyond the ENSO to the multi-winter warm pattern since 15-16. We will eventually see another cold winter in the Northeast. But I am not even sure what type of indication we would get before the season to make that call in October or November. The warmth has become so persistent that it’s uncertain what would be required to shift that pattern colder.

I only use the PDO in reference to what is happening north and northwest of Hawaii. The absolute PDO values are only relevant when it’s well coupled with the 500 mb pattern. I like Simon Lee’s 500 mb classification pattern since it emphasizes the more important 500 mb patterns. The Pacific ridge pattern is classic -PDO. And the Alaskan Ridge is closer to +PDO. It really simplifies things. The Alaskan ridge pattern drove the record +PDO in 14-15. But most winters since then have been the Pacific ridge. My guess is that the PDO is being driven more by what is happening in the WPAC tropics and subtropics. So the actual SSTs may only be secondary to the 500 mb patterns. But extended coupled phases probably reinforce each other.

These PDO fluctuations between -0.5 and -2.5 have been the norm this year. Notice the big up and down pattern since January. So we want to see some actual positives sustain to get a sense that the PDO is shifting. A cold pool would need to develop north and northwest of Hawaii for a true +PDO. This would be indicative of a more Nino-like Aleutian Low. But continued ridging near the Aleutians even if the PDO becomes more neutral is still problematic since it promotes a Western Trough and SE Ridge.

Same old model bias from recent years with the day 11-15 forecasts missing the ridge axis near the Aleutians and trough in the West. New run Old run

May be the first time the subsurface cooled so much under 1+2 and increased under 4 this time of year. No real oceanic kelvin waves to speak of just sloshing back and forth. So this year continues to do its own thing.

This has been the warmest more Niña-like -PDO pattern for Northern New England on record for the first half of October. Plenty of La Niña Octobers on the list.

The warm mins at Caribou are more impressive than the maxes. They are running +7.6 on the maxes and +10.0 on the mins. Still haven’t had their first freeze which is very late for them.

Finally getting a WWB pattern after the relaxation in September. So all regions except 1+2 have been rising. But Nino 4 continues to be the only region in record territory for this time of year. The strongest WWBs still lean west so Nino 4 may continue to be the stand out. Nino 3.4 needs to push back up above +1.7 to make some new highs for this event. But it’s uncertain how high it can go with the much cooler subsurface than the past strongest events like 15-16, 97-98, and 82-83. The one thing this year confirms is the importance of WWBs to move the El Niño forward as seen with the acceleration in August and slowdown from September into early October.

The Northeast is on track for another warmer October. Some parts of Maine are close to +10. Next few weeks look like more of the same.

While it’s true that the first group didn’t have a -PNA, it did have a trough near California which pumped the ridge over the NE for a warmer winter in the composite mean. That’s why I like using the 500 mb composites more often than than the raw indices. The raw PNA index for the composite below is +0.46. The Euro seasonal is showing a similar effect with a +PNA in Canada but a trough in the Western US. So the best outcome would probably be a strong PDO reversal or uncoupled -PDO. Then well coupled forcing near the Dateline and decent blocking on the Atlantic side. We just don’t want any competition from -PDO which can unfavorably interact with an El Niño pattern. A compromise we would like would be getting a dominant El Niño pattern with Atlantic blocking from late January into February. The Euro is trying to show something like this in the monthlies. Hopefully, it’s correct and not just defaulting to El Niño climatology.

I still think the subsurface looks more like a strong than super for Nino 3.4 in terms of ONI .Thinking the MEI peaks somewhere weak to moderate. Main concern is how strong the -PDO influence will be during winter? Plus we have the polar domain with AO and NAO which is always a wild card.

I like to look at the 500 mb composites. A strong -EPO is a classic El Niño response in October. But the ridge NW of Hawaii is more La Niña or -PDO. So far we are getting a blended composite telling us the El Niño is battling with the -PDO. This is why we are seeing the EPO fluctuations. Most other months of the year the PNA is the prime index that gauges how well El Niño or La Niña are doing.

The interaction with the coupled -PDO is what’s giving us the blended El Niño and La Niña October 500 mb composite.

Getting close to the all-time weekly record of +1.7 set in November 2015. But not sure what the daily record was back then. These WWBs displaced so far west instead of over Nino 3.4 are really putting a west lean on the most anomalous SSTs and forcing. +30C is the real deal.

The warm blob and NPAC ridge was displaced too far west last winter from the 13-14 more optimal position. Once that warm pool and ridge position pulls to the north and Northwest of Hawaii it becomes a problem for us. We need it closer to the West Coast for a better winter experience here.

Sometimes you just have to laugh.

It kind of looks like the WWBs so far west mostly allow Nino 4 to warm more while all the other regions stagnate or move sideways.

While the OP Euro is probably overamped at 500 mb in the SE, it’s still a good signal in the ensemble mean.

Pretty good ensemble support for another storm next weekend.

The Euro generally had the 500 mb pattern correct last winter. Notice how the ridge and trough axis longitudes worked out. But it underestimated the depth of the trough in the West. The East was particularly a good forecast indicating that the south based Greenland block would link up with the SE Ridge.