The ENSO region has cooled back down in the latest update.
The ENSO region has cooled down again in the past week, and very significantly so. The purple colours are starting to appear again on the eastern side of the ENSO region towards the Peruvian coast. Looks like a definite Weak La Nina signature to me. Moderate La Nina? I wouldn't put my bets on it but not ruling it out either. This has been such an unusual season for ENSO because the La Nina is getting going so late in the year and what makes it even more remarkable was the fact that it looked like we were going into an El Nino back in the Spring and June.
Here's last year's SST anomalies chart to compare. 2016/17 was a Weak La Nina Winter but it was among the weakest on record, that I'm pretty skeptical sometimes of how NOAA classify that as a La Nina event. You can see for yourself here that the ENSO region is much colder in 2017 than it was in 2016.
If you're wondering what are the effects of La Nina on the globe? Here's the chart for the Summer months showing a typical La Nina's global weather/climate impacts but remember that no ENSO event, including El Ninos, is the same.
The top one here is the impacts of La Nina on the globe in the Winter months.
SST anomalies in the ENSO region have ever so slightly warmed up a bit within the past week but not a huge rise in temperatures. However, what I can notice going by the anomalies here on this chart is that the coldest of the anomalies are going more towards the central part of the ENSO region rather than just off the Peruvian coast. This would foreshadow the signs of a central based La Nina, or La Nina Modoki. There hasn't been as much research done on La Nina Modoki events as there has been done on El Nino Modoki events (such as 2009/10). El Nino Modoki is basically the same as La Nina Modoki by the way, just that the anomalies are warm than cold. This is the only source I can really find information on for La Nina Modoki: https://www.graincentral.com/weather/are-we-heading-for-a-la-nina-modoki/
The source does not show much for us here in Ireland as ENSO's influence on Ireland and Europe is very variable and has plenty of different situations, depending on the event and the strength of it. Going by a reanalysis I did previously which showcased Weak La Nina Winters that were preceded by Weak La Nina Winters, a Weak La Nina is very good for 2017/18 but my question this week is, going by the current SST anomalies, what does La Nina Modoki hold for us? Is it good for cold Winters as much as El Nino Modoki? We'll have to see.
The CFSv2 continues to show a Weak La Nina event for 2017/18 but it has totally gotten rid of the chances of a Moderate La Nina taking place.
The JAMSTEC meanwhile is going for a borderline ENSO neutral to Weak La Nina.
The latest SST anomalies from NOAA prove my thoughts last week on that the La Nina was becoming more central based. Although at the same time, the La Nina has weakened. Still doesn't seem to be as weak as it was last year right now.
NOAA has officially said La Nina conditions for 2017/18.
EDIT: Sorry for the confusion.
In the past few weeks, there has been little to no difference in the ENSO region. The La Nina signature is still there. In fact, it's on borderline weak to moderate.
La Niña has intensified in the last week in the ENSO region marked. Not to mention, the south Pacific Ocean has also continued to cool down significantly which probably added to the intensification of the La Niña. As the cold pool in the south Pacific Ocean seems so deep and widespread, there is little to no sign of it warming up any time soon meaning that La Niña could intensify or last longer into Spring 2018.
The models continuing to struggle with predicting ENSO due to the turnover from El Niño to La Niña during the Summer. As a result, they have tended to play catch up.
The CFSv2 is clearly going for a Weak La Niña event although with the cold south Pacific Ocean waters, it could intensify into a moderate event, so watch this space.
No change in the Pacific in the past two weeks. La Nina is still firmly in charge.
4 weeks later, little to no change in the Pacific. We should be getting the Oct-Nov-Dec tri-monthly period anomaly within the next week or two from NOAA.
Despite the La Nina anomalies in the Pacific, the SOI is reflecting El Nino (the negative numbers in the daily column) a lot lately:
Did some research last week and it would appear that Arctic temps were at, and indeed, still are, at record high temps for the time of year. Current anomaly for the Arctic region is standing at +3.4c. You would think that with an La Nina in place over the last couple of months, that less heat would be transferring into the region, but this appears not to be the case.
The Oct-Nov-Dec anomaly was -0.9 which is within the Weak La Nina threshold, 3 more tri-monthly periods to go 'til we see if 2017/18 was truly a La Nina event.