E.N.S.O. Discussion

[blizzard81]

 Don You thinking about next winter already mate? We keep coming back for the punishment don't we?

[Don]

 blizzard81 yep, never learn…..

[summer blizzard]

Will update the weeklies when I get a chance but I wanted to highlight the difference as we approach September between 2023 and 2024.

 

[summer blizzard]

Here we go..

[northwestsnow]

Eric doesn't subscribe to the ECMWF  +NAO seasonal...

Hints of an East based Nina

 

Edited September 8, 2024 by northwestsnow

[SqueakheartLW]

A good sign that a developing EP La Nina amongst two other factors could be pointing towards a colder winter than average.

3 Signs that Winter 2024/2025 could be Colder than you might expect » Severe Weather Europe

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A colder than expected Winter 2024/2025 could develop over the United States, Canada and Europe, based on the 3 Oceanic and Atmospheric signs

Wouldn't take much to get a colder winter than the last one though.

 

[damianslaw]

Conflicting reading on whether a EP or central la nina anticipated.. well a comment on model thread says central expected. What to believe? 

[northwestsnow]

Latest ssts ...

[summer blizzard]

 damianslaw Gradient between west and east is very low (0.3) because the trades have been destroying the warmth left around Nino 4. 

We are forecast to see warming in the East Pacific during October thanks to the MJO and passage of tropical systems but this is likely temporary.

So I'd lean towards a weak west based Nina but if the sub-surface remains robust then we may see the event become more east based.

[summer blizzard]

I would not take much from it but if we are looking at La Nina which are first year and took time to get going then 95 and 05 are the best analogues. 2020 is next. 

 

[damianslaw]

 summer blizzard All three of these years saw quite a cold or a cold start to winter featuring varying degrees of northerly/easterly and anticyclonic influence. Indeed further cold weather occured Jan-Mar to varying degrees. 

[summer blizzard]

 damianslaw Indeed, all three were good however it's worth saying that winters 96 and 21 were at or just after solar minimum and that only winter 21 saw a +QBO. 

So none of them are that great as analogues. 

1983 and 1998 did also see relatively late developing NIna's but they were faster flips. Winter 99 is not a terrible analogue in terms of solar and QBO albeit this Nina is unlikely to reach similar strength. 

[SqueakheartLW]

 damianslaw  summer blizzard

There also seems to be something different about the start to this autumn too with lots of blocking highs which are mainly to our north giving us easterly winds already.

The polar vortex is also getting off to a slow start as well with below average zonal winds and even record breaking weak at times recently.

I think a major pattern shift started back in June 2024 when we switched from ridiculously mild and wet to something drier and cooler. It all seems to be tied in with the switch from El Nino back to La Nina and I've also noticed how all the major changes in the dominating pattern in the UK occur with a switch from a stronger ENSO state to another one.

[summer blizzard]

JAS ONI came in at -0.1.

Looking at years which saw a declared Nina but later than this we have..

1974

1983

1984

2005

2008

2017

Some were second year so 1983 and 2005 would the best matches if we get a declared event (potentially should in SON).

The winter of 1975 aside though, that’s not a terrible winter list.

 

 

 

[damianslaw]

Welcome updates on state of ENSO. 

[summer blizzard]

 damianslaw October will average about -0.4 most likely so cold-neutral however the RONI and MEI are already below weak Nina thresholds meaning that (probably thanks to the -PDO), the atmosphere is constructive. 

[summer blizzard]

Nino 4 has finally dropped below 0.

[summer blizzard]

3.4 fell to -0.8 and a wall of easterlies has been over the central Pacific.

Geronimo.

[SqueakheartLW]

The event is also CP which is killing off our winter now

[summer blizzard]

Nino 3.4 now down to -1.1 according to NOAA.

[Sceptilli0naire]

 summer blizzard I had no idea we'd reached moderate territory, I thought we were still at cold neutral. I wonder if it'll stick around long enough to be a declared event. Will be quite late if so as it'll have to stay below -0.5 until February to be an official event. Normally by February the extant ENSO phase is already starting to weaken

[Don]

25 minutes ago, Sceptilli0naire said:

I had no idea we'd reached moderate territory, I thought we were still at cold neutral.

Yes, looks rather ugly currently, being a CP event!

[summer blizzard]

[damianslaw]

Where are we with la nina, has it been called an official la nina? Is it CP based. A few posters are saying this bodes poor for cold in coming weeks, any reason why? 

[summer blizzard]

 damianslaw Because it developed so late, we can't be declared before at least May i think.

Yes, it's Nino 3.4 and 4 that are coldest (though these have the highest correlation with the atmosphere and the MEI has been in the Nina threshold since July).

Typically, a normal NIna tends to front load with a stronger polar vortex in the second half of the winter albeit -PNA conditions in the US often mean it can be mild and dry rather than full on zonal. Likewise, March-April in Nina years without a SSW can see -AAM conditions produce blocking for the UK.

In terms of this event, it's not really behaved like a normal event because we saw destructive MJO waves orbit the Pacific in September and November which produced an a-typical response in November and December. We have however seen January and the modelled forecasts for February produce a fairly typical global response and a Nina standing wave has also developed over the central Pacific (MJO locked into the Indian Ocean, roaring trades over the central Pacific).

With the polar vortex looking strong I'd therefore expect that Feb and March could be fairly settled but fairly mild.

- Worth remembering that this is very late in developing with 05 and 08 having previously been declared latest, most Nina events actually peak and weaken between Nov-April and wait until May-July before they start developing. In terms of analogues there are not really any that declare before May in the following year so we will either be declared as having entered the event in December (latest on record) or we will flop and be cold-neutral should the Nina go away.