bluewave

Yeah, the AI versions of the Euro have come further west also due to the stronger WAR than forecast. Figures the WAR would wait until September to finally put in a cameo this year. Plus any UL to our west could tug the storm even further west in later runs. Now we are back to the forecast bias of underestimating he WAR longer range only to correct stronger the closer in we get. This has been out pattern for years after a brief break over the summer. Figures it would be so difficult to sustain that for long with the record SSTs offshore. New run stronger WAR Old run weaker WAR

That 30 day period was in effect a super modoki El Niño. Nino 4 was the warmest on record near +30 C heading into winter. Greatest snowstorm on record in NYC around 30” and a below zero Valentine’s Day. So a greater snowstorm than all of the previous winter and a lower winter minimum temperature. But the extended cold and snow cover of the previous season was absent due to the higher background warmth following the ridiculous December 2015. I enjoyed the snowstorm quality in January 2016 more than any individual storm in 14-15. While there were numerous lows in 14-15 below 10° around NYC, It took until 2016 to actually dip below 0° for the first time since 1994. If the December rare MJO 4-6 didn’t happen, could have been a super El Niño with more extended snow and cold than any other.

There has been something off with every El Niño development since the super La Niña +13 pattern in December 2015. Heck, you can even go back to the El Niño that was supposed to develop in 2012-2013 which fizzled around Labor Day. But at least Nemo in February fulfilled the hoped for back-loaded El Niño pattern.

It looks another case of the WPAC warm pool slowing down the MJO from progressing past the Dateline this month.

You wonder what the magic number necessary these days is for a robust El Niño atmospheric response when +1.5 in Nino 3.4 hardly moves the needle.

Very weak event so far in regard to typical developing El Niño atmospheric response.

Most of the dynamical ENSO guidance are just repeater models. They exaggerate the conditions going forward that they were initialized at. When was the last time any of those models successfully forecasted a change from the state that they were initialized under until later in the game when it became obvious?

The GFS caved to the Euro on the NJ record September 100° heat on Thursday.

The AI version of the Euro which is now available free on their site was a little further west than the OP yesterday. But not quite as far west as the GFS.

Seasonal models seldom show nuances like that.

The evolution was driven to some extent by the record warming of the Gulf Stream boosting the SE Ridge. So the main reason it was rain had to do with the storm track. Cool the SSTs to the East Coast and that ridge would have been nonexistent with a near record -AO pattern for December.

Last December would have been colder and snowier if we had the colder -AO-PNA climatology from the 1950s and 1960s. Notice how much weaker the 500 mb lows were this past December. The -AO was the 2nd lowest on record for December with no strong 50/50 vortex to show for it. Even the -PNA upper low was weaker.

Looks like the heat peaks on Thursday with 98° on the GFS and 100° Euro for the usual warm spots in NJ.

Wonder if it’s possible to get a peak in 3.4 during October since there can be a 1-2 month lag between 1.2 and areas further west?

The 3.4 and 4 regions have been steadily rising while it looks like 1.2 has peaked. You can also see the subsurface heat spreading further west than it has been. The big question is if the early peak in the east allows 3.4 to reach 2.0 before it levels off for a while?

The nature of the 500 mb or surface patterns that those indices represent has been changing. We have been seeing expansion of the ridges and shrinking of the troughs associated with the teleconnections. Simon Lee has really simplified the indices down to several well observed 500 mb patterns. It’s a great paper.

My main question with that is how fast the forcing reversed once the record IOD peaked back in the fall of 2019. This IOD appears that it will be weaker than that one. Plus we had WPAC Nina-like MJO forcing activity following the IOD peak in the fall of 2015. Doesn’t need to go completely neutral for a rebound in WPAC SSTs. We can remember the record breaking SST rebound near Indonesia and Australia during our winter in 19-20.

That’s not the point though. Of course Nino 4 is warmer than the eastern zones. But it’s the magnitude of the temperatures in that region and the WPAC which are higher than we saw back in years like 1997. So this is why the forcing was pulled much further west this summer vs 1997. We have to look at threshold temperatures in the various regions to determine where the forcing sets up. Now we have larger warm pools of +30 C SST heat which act as forcing magnets. 1997 had no such competition for forcing so the central to eastern zones were able to run the show. This hasn’t been the case so far in 2023.

That’s due to the size of the troughs shrinking relative to similar teleconnections in the past. The trough was only to get as deep in a more limited area of the Mid-Atlantic. In a cooler climate, the record -EPO+PNA -NAO would have produced similar temperatures to 2009 with a much more expansive trough. We have seen similar instances of the warming teleconnection pattern across all seasons. The record -AO and -PNA last December should have been much colder and snowier in the Northeast had it occurred back in the 1950s to 1970s. Many cold and snowy -PNA -AOs back in the old days. But it’s a rarity to get cold -PNAs these days. Even -AO +PNA patterns are getting warmer as was the case with the Christmas flood cutter in 2020. Don also hade a great series of posts on the warming -AO and -NAO patterns.

I used June and July to illustrate the point when the trough was at its deepest Ike back in 2009. Were were discussing this in the NYC Metro forum. This should have been a much cooler summer for the region than it was vs past blocky developing El Niño summers. The expanding ridges with record 500mb heights have become a staple of our new climate. All teleconnection combos are getting warmer.

It was nearly as deep in the mid-Atlantic. 2nd lowest June and July heights on record there. But the aerial coverage of the trough was much smaller due to the steadily expanding 500 mb heights since 2009. The ridges were much more expansive this time around leaving smaller and warmer troughs.

That’s the point that I have been making. While the trough in the mid-Atlantic was nearly as deep this June and July as 2009, there was much less cool air available. This is due to the expanding 500 mb ridges pressing in around the smaller troughs. So record 500 mb heights are leading to much less colder air available for the shrinking downstream troughs. This is a very important aspect of a warming climate which gets little discussion. Troughs decades ago were much more expansive and colder.

Case and point this summer. Should have been much cooler in the U.S. this summer with the near record -NAO-EPO+PNA pattern. 2009 featured roughly similar teleconnections and we were significantly warmer than that summer was. Troughs have been getting crowded out by ridges as the 500mb heights keep rising.

I think we are probably on the same page with our concerns about another mild winter coming up. But we arrive at that potential from two different directions. I believe your concern is that the eastward lean to the SST anomalies finally pulls the forcing east as we head into the winter. I am wondering if the El Niño peaks a little early and the forcing stays near the dateline. Then if there are coupling issues like we have seen this summer, the MJO 4-6 forcing which is also warmer could factor in at times. Plus strong enough dateline forcing in itself could be mild if the PNA ridge rolls over into the Northeast. So it may come down to whether we can get some snowfall luck in a mild pattern and a well timed STJ and blocking overlap. Let’s face it, there are more warmer potential forcing scenarios than cold as we have seen every winter since 15-16. 14-15 was such a freak event with the mega -EPO block overpowering the record +NAO. It was a Modoki with a raging +NAO. Since the climate has warmed so much since then, not even sure if similar modoki forcing scenario would even yield a very cold winter again.

If Philly can hit 100°, then Newark most certainly will. Record heat building into Philly usually makes it up to Newark. So there should be at least one day with favorable winds and highs from 97° to around 100°. Same goes for big Philly snowstorms making it to around Newark with the rare exception of 2-6-10. But we won’t have a 5 SD block this week like back then.