E.N.S.O. Discussion

[Snowy Hibbo]

The JAMSTEC forecast was released yesterday.

It forecasts a Borderline La Niña like many models released this month. 

It is one of two models, that consider El Niño Modoki, which is forecast to be neutral.

Another model that doesn't seem to have been mentioned here much is the EC model. It shows a weak-moderate La Niña occurring.

[summer blizzard]

[jvenge]

CFSV2 is backing off on the La Nina with each run. Still there, but it has weakened a lot.

 

[summer blizzard]

45 minutes ago, jvenge said:

CFSV2 is backing off on the La Nina with each run. Still there, but it has weakened a lot.

 

It seems quite a reactive run in that whenever we have seen a burst of westerlies it has backed off rather than assume they'll be cancelled out by a burst of easterlies down the line. 

[Summer Sun]

 

[jvenge]

1 minute ago, Summer Sun said:

 

Hi,

I think thats a little outdated already. The strength of the La Nina has weakened on models over the past 3 weeks.

[sebastiaan1973]

Lot's of diversity with weak La Nina winters.

[Paul_1978]

https://twitter.com/SimonLeeWx/status/922202411921526784

[summer blizzard]

As ever the weather loves to be unpredictable. 

So firstly our current anomolies are at -1.4 and -0.8 respectively. 

However.. 

The westerlies (probably MJO related) have completed their first full cycle since at least April.

However.. 

Sub-surface anomolies are now very strong and still getting colder. 

..

Seems to me like this is either a last gasp or we are seeing a game of chicken, if we get another surge in the trades for a few weeks then we are going full Nina with those sub-surface anomolies. If we see repeated MJO cycles, the atmosphere may try fight. 

Edited October 25, 2017 by summer blizzard

[Paul_1978]

There's a lot going on there @summer blizzard - could you simplify it for us mere mortals? Many thanks 

[jvenge]

CFSv2 is sticking to a range of between -0.7 and -1.0 the past few weeks. Not quite sure how other models are viewing it yet. Staying within this range should make a seasonal outlook easier, though.

Edited November 1, 2017 by jvenge

[Catacol]

If UKmet follow the same path and weaken their Nina forecast then the November glosea update might be interesting...

[summer blizzard]

Interestingly it turns out that the NOAA when they issue ONI monthly data (La Nina/El Nino) have over the years been changing the anomaly period every decade to the most recent 30 year average (so a -1 reading in 2007 is not the same as one in 1996). So a guy on another forum has essentially reset the data against a 1950-2010 average so that it's a level playing field so to speak. 

Most interesting though is that the guy in question did it for both 1.2 and 3.4 and it turns out that for the DJF period we have not actually had a La Nina in 1.2 since 1984, it also shows significantly that 1.2 never really left El Nino behind until early this year. 

With our current pattern looking like it may be able to deliver a DJF Nina in 1.2 i thought it interesting to look at the anologues.. 

1984

1980

1975

1974

1973

1970

1967

1962

1956

1955

1954

1953

1950

If we exclude the winters that averaged >1.1 along with second/third/4th year Nina's then we get..

1984

1980

1962

1953

1950

Those winters contained..

2 warm

4 average

9 cold

In terms of months, a clear bias. 

Moral of the story - pray for the east based Nina. 

 

[Paul_1978]

I read on Twitter that the current/predicted La Nina is east based.

I then found this really old post from this forum with some thoughts about an east-based La Nina and the effect on Europe.

Any thoughts on this anyone?

[Summer Sun]

 

[Paul_1978]

4 hours ago, Summer Sun said:

 

Interesting, but the tweet shows America - how about the effect on Europe?

[feb1991blizzard]

1 minute ago, Paul_1978 said:

Interesting, but the tweet shows America - how about the effect on Europe?

That's a good height anomaly over Greenland for a week 4 ensemble mean (which I presume it is) forecast.

[Summer Sun]

 

[BornFromTheVoid]

On 05/11/2017 at 12:39, summer blizzard said:

Interestingly it turns out that the NOAA when they issue ONI monthly data (La Nina/El Nino) have over the years been changing the anomaly period every decade to the most recent 30 year average (so a -1 reading in 2007 is not the same as one in 1996). So a guy on another forum has essentially reset the data against a 1950-2010 average so that it's a level playing field so to speak. 

Most interesting though is that the guy in question did it for both 1.2 and 3.4 and it turns out that for the DJF period we have not actually had a La Nina in 1.2 since 1984, it also shows significantly that 1.2 never really left El Nino behind until early this year. 

With our current pattern looking like it may be able to deliver a DJF Nina in 1.2 i thought it interesting to look at the anologues.. 

1984

1980

1975

1974

1973

1970

1967

1962

1956

1955

1954

1953

1950

If we exclude the winters that averaged >1.1 along with second/third/4th year Nina's then we get..

1984

1980

1962

1953

1950

Those winters contained..

2 warm

4 average

9 cold

In terms of months, a clear bias. 

Moral of the story - pray for the east based Nina. 

 

They update every 5 years based on the centered 30 year average, this is to account for the general rise in ocean temperatures. So the period of say 1986 to 1990 will have it's ONI calculated from the 71-2000 based period. This is applied retroactively, so the current values are based on the 86-15 average, but will change every 5 years until we have the full 01-30 base period to calculate the final anomaly from.

One of the important aspects of ENSO is the sea surface temperature anomaly created across the equatorial Pacific during the different ENSO phases, rather than the absolute temperature. So if an area appears warm compared to the 51-10 average, but is essentially normal compared to the last 30 years or even current sea surface temps, it wont have the same kind of impact as a similar absolute temperate 50 years ago.

All of this makes it especially tricky to tease out whatever influence that ENSO my play in our weather, especially with the myriad of other factors to consider!

[Summer Sun]

 

[damianslaw]

Interesting analogue analysis above, 1962 cropping up, indeed more average/colder than average winters than above under an east-base La Nina. We must remember ENSO is only one factor, and can be cancelled out by others, much like last winter which had a strat/trop disconnect. Its too simplistic to base predictions of a season ahead on effect of ENSO alone.. Our weather is a concoction of variables, and recent years have seen anomalous deviations from predicted behaviour - the failed easterly QBO being just one..

 

[Summer Sun]

 

[Summer Sun]

 

[V for Very Cold]

Quote

Well that's a hint of encouragement for us coldies!

 

[summer blizzard]

The latest weekly SST departures are: Niño 4 -0.3ºC Niño 3.4 -1.1ºC Niño 3 -1.2ºC Niño 1+2 -1.2ºC.