sryanbruen Registered User

The last month has been quiet for ENSO with neutral conditions but it has suddenly gotten very interesting. The SOI for June of -10.4 showed that the atmosphere over the Pacific was in an El Nino setup and there was not a single day with La Nina (i.e. positive SOI values) values. However, July has been a different story with many La Nina SOI days: There was some very positive SOI days especially the 20th and 21st July. However, unlike June, there still have been some days where the atmospheric setup was in favor of El Nino according to the SOI in July. Right now it's rather positive thus in favor of La Nina.

The Pacific waters looking at the below chart are cooling down significantly from where they were in Spring and early Summer. At the same time, the PDO is becoming positive i.e. warm compared to how cool it was in Spring. These are very interesting times for ENSO. Could we have another Weak La Nina for the second Winter in a row or will we stay neutral? I think we will stay neutral but as can be seen from last Winter which was arguably the weakest La Nina on record, it can be a La Nina event regardless of how weak it looks.

The CFSv2 shows the possibility of a Weak La Nina but it reaches the threshold in early 2018 which is weird cause you'd expect the La Nina to start going back to neutral - normally around that point rather than getting more intense. Anyway it's a long way off and you can see how disastrous the models have been with predicting this ENSO as previously they were showing El Nino.

To finish off this update, I want to give you guys something exciting. If a Weak La Nina were to come off, it'd be a good chance for a cold Winter going by previous occurrences of Weak La Nina to Weak La Nina winters. This reanalysis shows low pressure to the south, high pressure over Scandinavia with the winds coming from an easterly. There is only one bad Winter in the mix, 1909/10 which was a terrible Winter but it was at least average for snowfall. If not a cold, snowy Winter then another anticyclonic Winter like 2016/17 again that the reanalysis shows.

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sryanbruen Registered User

Little to no sign of La Nina from the models. The majority of them are on the warm side of neutral to perhaps Weak El Nino status.

Akrasia Registered User

I know we've had a double El Nino which was considered rare, how rare would 3 el ninos in a row be?

Are we talking about totally unprecedented here? And might it indicate a breakdown of the southern oscillation as we used to know it?

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