As the doors have been closed on ENSO 2017/18 with it officially being a weak La Niña season, it's time to move onto ENSO 2018/19! Given how last year evolved, I thought I'd hold off on making a new ENSO thread for a bit. If you do not know what happened last year, 2016/17 was a very weak La Niña season (weaker than 2017/18) beginning in July 2016 and already gone by late 2016 with ENSO neutral occurring in early 2017. The waters started to warm up with some significant warmer than average SSTs developing in the eastern side of the equatorial Pacific in Spring 2017. It was looking increasingly likely that an El Niño was in the works for 2017/18. The SOI for June 2017 was very negative with an index of -10.4, the most negative the SOI was since April 2016 at this time. A negative SOI is reflective of El Niño whilst positive is La Niña. The models, especially the CFSv2, was pinpointing at a moderate to strong El Niño for 2017/18 as a result. There were even a good few ensembles going for a very strong El Niño, just 2 years after the previous one (a very strong El Niño has occurred in only 1877-78, 1982-83, 1997-98 and 2015-16). However, a dramatic turn around occurred in July 2017 with the SOI going positive at 8.1. Not to mention, the equatorial Pacific waters cooled down a lot from Spring and June. Every month from July to November 2017 had a positive SOI whilst December went negative meaning the La Niña that was going to take place wasn't going to be particularly strong but it was stronger at least than 2016/17 which had a pathetically weak La Niña. Now with that behind us, let's get onto 2018/19.
Here is the latest SST profile from NOAA for the 24th May 2018. I have highlighted the region we're interested in, the equatorial Pacific. The La Niña signature is well and truly gone with the warm waters overtaking it.
For the central part of the Pacific (ENSO region 3.4), the CFSv2 right now is depicting a weak El Niño for 2018/19.
However, if we look towards the eastern side of the Pacific (ENSO region 1+2), the CFSv2 is showing ENSO to be neutral for 2018/19.
When you have the origins of an El Niño occurring in the central part of the Pacific, it's called El Niño Modoki. This is a rare form of El Niño where the warming is focused on ENSO region 3.4 in the equatorial Pacific - usually you see warmings beginning in the eastern part of the Pacific.
Here's a diagram showing the ENSO regions.
El Niño Modoki events tend to be favourable historically for blocked Winters in Europe. The last El Niño Modoki event occurred in 2009-10. It has also occurred in 1979-80, 1986-87, 1990-91, 1991-92, 1992-93, 1994-95, 2002-03 and 2004-05.
If this El Niño Modoki outlook continues up to the latter part of this year, it will make for some very interesting discussion on the coming Winter. Anyway, let's not worry about that for now.
The warm subsurface temperature anomalies are still there in the Pacific so El Niño is quite likely at this rate. Will it be Modoki? We'll have to see.