What does El Nino mean for the UK Winter? (Merged)

[North-Easterly Blast]

Looking at this week's SST anomaly chart it does seem to show warm anomalies of the west of Central South America. Does this suggest that an El Nino event will develop later this autumn and into winter? There was a strong El Nino in 1997-98 and we all know how disastrously mild a winter that turned into for the UK at least. Warm anomalies are also present east of Newfoundland too, and I wonder what effect that will have on our weather patterns and synoptics.

[BLAST FROM THE PAST]

Looking at this week's SST anomaly chart it does seem to show warm anomalies of the west of Central South America. Does this suggest that an El Nino event will develop later this autumn and into winter? There was a strong El Nino in 1997-98 and we all know how disastrously mild a winter that turned into for the UK at least. Warm anomalies are also present east of Newfoundland too, and I wonder what effect that will have on our weather patterns and synoptics.

NEB

I think this has been covered on another thread however it is anticipated that a weak EL NINO will form at worst/best and as for strong EL NINO conditions this should have happened sometime ago and so it is beleived very unlikely that moderate to strong EL NINO conditions to form. Re Newfoundland that is a signal for potential positive NAO conditions with LPs blasting off there towards the UK...BUT there are other teleconnections to also consider and so it could be positive or negative re UK winter chances

BFTP

[North-Easterly Blast]

Yes, warm anomalies to the east of Newfoundland may encourage positive NAO conditions but why not zonality of a polar maritime origin?

[Glacier Point]

What does El Nino mean for the UK Winter ? Probably one of the most frequently asked questions at present. The ultimate answer is that no one factor will influence our weather totally but by looking at the main attributes of this teleconnection, we can at least attempt to put one piece of the winter jigsaw into place.

To start, the current status of the El Nino Southern Oscillation (ENSO) is in a positive phase. There are many measures, but my favoured one is the Multivariant ENSO index or MEI:

http://www.cdc.noaa.gov/Correlation/mei.data

During July and August we recorded MEI values in excess of 0.5 - the monthly threshold of an El Nino. Usually, an El Nino has to span a 3 month period before officially declared although this would appear to have been reached according to the latest NOAA advisory:

http://www.noaanews.noaa.gov/stories2006/s2699.htm

The current Sea Surface Temperature Anomaly (SSTA) and mid-water profile of the equatorial waters strongly suggest that this 'weak' El Nino will continue into the next few months, a view endorsed by most of the major modelling:

http://weather.unisys.com/surface/sst_anom.html

http://img444.imageshack.us/img444/4973/wkxzteqanmvb7.gif

http://iri.columbia.edu/climate/ENSO/currentinfo/figure3.html

http://www.met-office.gov.uk/research/seasonal/elnino/index.html

http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing/sstaa.gif

Note here that most of these latest outputs were made before the large warming recorded towards the end of August, probably making these under-estimates as too the likely strength and duration of +ve MEI conditions.

By looking at the composite anomalies for Dec-Jan-Feb under MEI conditions 0.5 to 1.5 to capture the range between weak and moderate strength E Nino's, we have a reasonable size sample. This reanalysis suggests a number of strong likelihoods in terms of pressure patterns and temperatures.

The most striking signature of a weak to moderate El Nino are its zonal and vector wind anomalies. Warm equatorial waters lead to a strong thermal gradient to the north and south leading to stronger westerly (N. Hemisphere) winds over the southern 'States. These are accompanied by an increased -ve anomaly or trough in the eastern Pacific and likely jet stream displaced southwards in the Atlantic.

These help explain the pressure anomaly patterns with notable troughs in the eastern Pacific, over central and eastern Siberia (likely to pump cold air southwards into Russia) and -ve height anomalies over the central Atlantic with a hint of weak ridging over western Europe.

In terms of temperatures, El Nino tends to lead to a moderately mild winter for the UK and NW Europe, probably due to the influence of the mean ridge.

However, this analysis masks considerable inter-month variability. Compare the temperature and 500 hPa height profiles for the three months:

Decembers tend to be about average, Januarys tend to be significantly below average with a very negative Arctic and North Atlantic Oscillation pattern, whilst Februarys tend to be on the mild side.

Now, turning to the possible impacts this winter, I would pick out the following:

1) The west North Pacific is anomalously warm which, if it continues into the next two months, will serve to maintain a strong Pacific High and east Pacific trough enhanced by the colder surface waters there - developing quite an amplified long wave pattern.

2) The colder SSTAs within the tropical Pacific and Atlantic will serve to strengthen the thermal gradient and increase the zonal and vector wind anomalies along the lines shown - strong sub-tropical jet likely to support greater pressure over Greenland and increase the chances of displaced polar jet flow.

3) The overall reanalysis points towards lower pressure in the central Atlantic which coincides with the colder SSTA there right now. The warmer anomalies are essentially to the north of this making it likely that the polar jet flow will be weaker than normal and for low pressure systems to take a progressively lower track. In effect, I see this as a clear signal for the current (-ve) North Atlantic Oscillation to be enhanced by the presence of a weak to moderate El Nino.

4) We are now at the low point of the solar flux .

We have also to recognise increasing global temperatures and the potential for an above average December to disrupt the build-up of cold continental air. The use of any comparisons must also reflect the massively polar temperature anomalies.

Given these I will follow the SSTA and October / November temperature outturn with great interest. If we observe a more traditional Autumn pattern and the north Atlantic warm anomalies stay as they are now, then I would suggest we could well be looking at an overall winter with some significant and often extreme weather conditions - both mild and cold.

GP

Edited September 16, 2006 by Glacier Point

[blitzen]

Hello GP, Although your post is way above my head, I still find it interesting and thankyou. You refer in your post to a more traditional Autumn pattern. Can you explain more traditional? ie: are they mostly traditional, sometimes traditional or hardly ever traditional nowadays.

[Glacier Point]

Hi Blitzen,

as we progress through October and November, we should see the influences of El Nino, and in particular the implication for pressure to fall in the Atlantic. Although we may well be within a ridge scenario with high pressure to our south and east, we are more likely to see storms making their way across the far NW and perhaps a quieter interlude into November with fog and frost as the mid and higher latitudes start to cool down rapidly.

GP

Edited September 16, 2006 by Glacier Point

[johnholmes]

hi GP

As to your post I have never really followed let alone understood much of your points. However, since reading them over the past year or so I have begun to understand a good deal more. For that my thanks to you for the easy way in which you write with all the necessary relevant threads to read. A really first class post and again many thanks.

I do hope it does not get lost in the multiplicity of will it or wont it winter posts.

mods/admin may the post by GP be pinned in the relevant section please?

John

[Dawlish]

hi GP

I see no need to repeat your superb analysis and often wonder why others do! Small niggly point by me.

As to your post I have never really followed let alone understood much of your points. However, since reading them over the past year or so I have begun to understand a good deal more. For that my thanks to you for the easy way in which you write with all the necessary relevant threads to read. A really first class post and again many thanks.

I do hope it does not get lost in the multiplicity of will it or wont it winter posts.

mods/admin may the post by GP be pinned in the relevant section please?

John

Maybe a section for individual's winter forecasts? I too hope this won't get lost.

I do understand the various relationships and possibilities in there GP. I marvel at your capacity for weaving them together into a believable whole. It takes a terrific amount of knowledge and imagination to link them. It wouldn't be possible to write what you do, without a great depth of understanding and a terrific dedication to following and remembering/storing the past to use again in a future post.

I dunno overall!! You know my views on the accuracy of LRF, generally, but I do broadly agree with your basic conclusions about the possible effects of an El Nino on the UK.

Firstly there is the overall, global effect of warming; dependent, of course, on the strength of the developing oscillation. We can't be entirely isolated from that, though it woudn't be a simple feed of heat to NW Europe. From that, develops my agreement that there could be some quite wild swings between cooler and warmer conditions as the global atmosphere adjusts to a significant, unusual input of tropical, Pacific, heat.

Combining the two would give an overall milder than average winter, some cooler periods and snow, certainly, but with the main extremes being milder ones. Perhaps we could see temps close to a monthly record in Jan/Feb, but even more likely through next spring and summer, as the El Nino develops. Some of this is reflected in the odds I've offered for the winter months. The odds on very high CETs in DEC/JAN/FEB, are not long - as West has already mentioned!

I echo John's hopes and I really wouldn't like to see your forecast, and other's like summer blizzard's lost. Even though I don't set a lot of store by individual's LRFs ( absolutely no offence to any of you, really, keep up the excellent work, it drives your meteorology and helps others with theirs), they are a terrific teaching tool. I'd encourage anyone to take the time to really go through GP's forecast and read his excellent annotations. It gave me 15 minutes of complete absorption; remembering my past learning and even clicking onto a couple of sites and a trip to a textbook to check!! It would be great to go back over them all in spring (I'm sure many of you will anyway, to see what went as planned and what may not have done).

Just: thanks

Paul

Edited September 16, 2006 by Dawlish

[BLAST FROM THE PAST]

Yes, warm anomalies to the east of Newfoundland may encourage positive NAO conditions but why not zonality of a polar maritime origin?

Yes on its own but with other signals it is anticipated that the southern arm of the jet will be more of a player forcing LPs to come off the states on a southerly track. My personal view is that we are in for a 77/78 style winter, highly variable but with some decent winter storms. Have a look at the archive charts and you'll see what I mean. That winter produced very mild +16c days and also bouts of 15 feet drifts of snow. The arctic seems to give out signs that it may want to play ball [see carintians reports for that] and look at GPs tele forecasts for further signals.

Just want to add too that another LRF site [uS] which claims 80% accuracy are forecasting a below average and pretty snowy winter for the Carolinas....hinting at low Jet trajectory kicking out of the States?

BFTP

Edited September 16, 2006 by BLAST FROM THE PAST

[disco-barry]

What IS el nino?

[johnholmes]

this is perhaps a good starting point

http://www.elnino.noaa.gov/

John

and this

What is El Niño? The oceanic and atmospheric phenomenon known as El Niño occurs in the Pacific Ocean when the western coasts of Ecuador and Peru experience unusually warm ocean conditions that cause climatic disturbances of varying severity. The term is used to describe exceptionally intense and persistent occurrences, although originally it described the warm southerly current that appears in the region every December. These extreme climatic conditions occur every three to seven years and can affect climates around the world for more than a year. The name El Niño, Spanish for "the child," refers to the infant Jesus Christ and is used because the current usually begins during the Christmas season. The phenomenon is know as the El Niño Southern Oscillation, or ENSO, because El Niño is accompanied by a flux in air pressure and wind patterns in the southern Pacific.

What happens during El Niño? El Niño causes climatic disturbances when sea surface temperatures in the southeastern tropical Pacific are abnormally high. Usually, the warm waters are restricted to the western tropical Pacific, where temperatures are higher than the eastern waters of coastal Peru and Ecuador by more than 10 degrees Celsius. The air pressure is low over the warmer waters and moist air rises, resulting in the clouds and heavy rainfall typical of southeastern Asia, New Guinea, and northern Australia. In the eastern Pacific, the water is cold and air pressure is high, creating the characteristically arid conditions along coastal South America. In the east cold water rises to the surface as warm surface water is pushed westwards by the trade winds blowing from east to west.

However, during El Niño, the easterly trade winds subside and sometimes change direction. This causes a change in sea surface temperatures and increases in wind and pressure changes. Sea surface temperatures along the western coast of South America experience a substantial increase while the warm water of the western Pacific flows back eastward. As this happens, there is a shift in weather patterns - wet weather conditions normal to the western Pacific move to the east, and the arid conditions common in the east appear in the west.

What are its consequences? The shift in normal weather conditions can result in heavy rains in South America, and droughts in southern Africa, southeastern Asia and India, as well as unusual weather to parts of North America. El Niño also has economic consequences, for example in coastal Peru and Ecuador many industries and livelihoods are upset by the destruction of fish and bird populations due to a shortage of nutrients in the water.

What is La Niña? La Niña is characterized by unusually cold ocean temperatures in the Equatorial Pacific, compared to El Niño, which is characterized by unusually warm ocean temperatures in the Equatorial Pacific. (<A href="http://www.pmel.noaa.gov/toga-toa/la-nina-story.html" target=_blank>See the NOAA site for more explanation)

Edited September 16, 2006 by johnholmes

[summer blizzard]

Yes on its own but with other signals it is anticipated that the southern arm of the jet will be more of a player forcing LPs to come off the states on a southerly track. My personal view is that we are in for a 77/78 style winter, highly variable but with some decent winter storms.

BFTP

It is interesting that you say that, because the most favored anologue for me is the 1977 one..

[Glacier Point]

Thanks all for your comments so far.

The one thing I would like to point out is that my earlier post was not intended as a forecast. There is much time for things to change and the SSTA could rapidly change between now and the end of November. This was really an assessment of what implications one particular, but none the less very important aspect of circulation could have into the winter months given the situation now.

As for the use of analogues, I would caution here. We live in unprecedented times where we face massive polar anomalies and indeed, a time when the north Atlantic has not been so extensively warm. 1977/8 does tend to fit a number of variables quite well, but the SSTA preceeding that winter bore limited resemblence to the current in respect of the warm North Atlantic. I prefer to look at the inferences from various analogues and see how these might fit together best.

[summer blizzard]

Glacier Point, i forgot to say that it is a very good post and backs up my thoughts.

While it is true that the current sea surface temperature anomoly could change rapidly, at the moment, both the Pacific and Atlantic Oceans are conducive to a more faviourable cold setup, some of this obviously caused by the developing El Nino.

Also, i thought that the pole was actually above average at the moment, and has been since the end of August, we may have approached this Autumn from a higher baseline however that baseline is below that of 2005 now in terms of both Polar and sea surface temperature anomolies??

[BLAST FROM THE PAST]

It is interesting that you say that, because the most favored anologue for me is the 1977 one..

Indeed I think it is the nearest example for what lies ahead. I will ask that many caution on the arctic anomalies...they were much warmer in the late 30s and 40s and winters became very harsh...the arctic is not unprecedently warm...far from it.

BFTP

[summer blizzard]

Unfortunately, that is only my favoured MEI anologue at the moment and given that only a weak to moderate El Nino is expected this winter, i doubt it will be a leading mode.

[summer blizzard]

Thanks all for your comments so far.

The one thing I would like to point out is that my earlier post was not intended as a forecast. There is much time for things to change and the SSTA could rapidly change between now and the end of November. This was really an assessment of what implications one particular, but none the less very important aspect of circulation could have into the winter months given the situation now.

As for the use of analogues, I would caution here. We live in unprecedented times where we face massive polar anomalies and indeed, a time when the north Atlantic has not been so extensively warm. 1977/8 does tend to fit a number of variables quite well, but the SSTA preceeding that winter bore limited resemblence to the current in respect of the warm North Atlantic. I prefer to look at the inferences from various analogues and see how these might fit together best.

I believe that the change in the sea surface temperature anomoly setup is one of the reasons why the Met Office have gone for an average winter as opposed to a mild one recently.

I agree about the Polar anomolies however overall the Atlantic was warmer in 2005, as evidenced by the AMO.

http://www.cdc.noaa.gov/Correlation/amon.us.long.data

In terms of anologues, 2004 is the most favoured anologue at the moment given that out of nine teleconnection patterns, it is an August anologue for five of them.

[Glacier Point]

In terms of anologues, 2004 is the most favoured anologue at the moment given that out of nine teleconnection patterns, it is an August anologue for five of them.

Have you tried 1969 ? Perfect match-up on the Summer pattern thus far and seems to be tracking the September and likely October warmth quite well. Only problem is that this was a peak solar cycle year (quite opposite to now)hence my problems with placing too much store in single year analogues.

In so far as El Nino, is that cold water I see off Peru ?

http://weather.unisys.com/surface/sst_anom.html

GP

[summer blizzard]

Here are the anologues...

http://www.netweather.tv/forum/index.php?s...31951&st=34

1969 matches three of the nine teleconnection anologues and is a good match in the Atlantic however there are differences in the pacific which is why 2004 is a much better match.

Edited September 21, 2006 by summer blizzard

[matmilne]

average winter sounds good to me. but last year was supposed to be a dry and warm winter and we had the worst snow fall in 50 years (though it did all fall in 2 weeks in march).

if we could get a white christmass for a change that would be great.

The main thing for us about elnin is that the jet should be pulled further south resulting in the polar air mass coming further south than it did last year bringing generally colder conditions to the uk at various points. When it's warm it may be warmer the you'd expect, when it's cold it could be much colder than you'd expect.

But it really all depends on how the main elements develop.

What effect an early start will have on enin's progress is the question.

[stormchaser1]

evening everyone

Im sure ive read that there was a EL NINO in 2001 [ i may be mistaken by this year if i am i apologise]

if there was a El Nino in this year , could someone please tell me whether this was a strong Nino or A weak NINO ,

many thanks

nigel

[Dawlish]

evening everyone

Im sure ive read that there was a EL NINO in 2001 [ i may be mistaken by this year if i am i apologise]

if there was a El Nino in this year , could someone please tell me whether this was a strong Nino or A weak NINO ,

many thanks

nigel

Not really(!), is the best I can do Nigel. There have been lots of predictions of El Nino conditions since the last major one in 1998, but, although temperatures in the equatorial Pacific have varied, there has not been a true El Nino since 1998.

This was one such prediction in Jan 2002, which implies that there wasn't an El Nino in 2001. Could I hell find a graph of El Nino years! Maybe someone else can help.

Regards, Paul

[stormchaser1]

Not really(!), is the best I can do Nigel. There have been lots of predictions of El Nino conditions since the last major one in 1998, but, although temperatures in the equatorial Pacific have varied, there has not been a true El Nino since 1998.

This was one such prediction in Jan 2002, which implies that there wasn't an El Nino in 2001. Could I hell find a graph of El Nino years! Maybe someone else can help.

Regards, Paul

cheers for that Paul

Reason im trying to find out ,is because of my stats i have for 2001, overall it was a very cold year for the north east , especially, jan, feb, march, and april ,and im just doing a bit of research at the moment

nigel

well you should know me by now

[bigboblee]

What does El Nino mean for the UK Winter ? Probably one of the most frequently asked questions at present. The ultimate answer is that no one factor will influence our weather totally but by looking at the main attributes of this teleconnection, we can at least attempt to put one piece of the winter jigsaw into place.

To start, the current status of the El Nino Southern Oscillation (ENSO) is in a positive phase. There are many measures, but my favoured one is the Multivariant ENSO index or MEI:

http://www.cdc.noaa.gov/Correlation/mei.data

During July and August we recorded MEI values in excess of 0.5 - the monthly threshold of an El Nino. Usually, an El Nino has to span a 3 month period before officially declared although this would appear to have been reached according to the latest NOAA advisory:

http://www.noaanews.noaa.gov/stories2006/s2699.htm

The current Sea Surface Temperature Anomaly (SSTA) and mid-water profile of the equatorial waters strongly suggest that this 'weak' El Nino will continue into the next few months, a view endorsed by most of the major modelling:

http://weather.unisys.com/surface/sst_anom.html

http://img444.imageshack.us/img444/4973/wkxzteqanmvb7.gif

http://iri.columbia.edu/climate/ENSO/currentinfo/figure3.html

http://www.met-office.gov.uk/research/seasonal/elnino/index.html

http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing/sstaa.gif

Note here that most of these latest outputs were made before the large warming recorded towards the end of August, probably making these under-estimates as too the likely strength and duration of +ve MEI conditions.

By looking at the composite anomalies for Dec-Jan-Feb under MEI conditions 0.5 to 1.5 to capture the range between weak and moderate strength E Nino's, we have a reasonable size sample. This reanalysis suggests a number of strong likelihoods in terms of pressure patterns and temperatures.

The most striking signature of a weak to moderate El Nino are its zonal and vector wind anomalies. Warm equatorial waters lead to a strong thermal gradient to the north and south leading to stronger westerly (N. Hemisphere) winds over the southern 'States. These are accompanied by an increased -ve anomaly or trough in the eastern Pacific and likely jet stream displaced southwards in the Atlantic.

These help explain the pressure anomaly patterns with notable troughs in the eastern Pacific, over central and eastern Siberia (likely to pump cold air southwards into Russia) and -ve height anomalies over the central Atlantic with a hint of weak ridging over western Europe.

In terms of temperatures, El Nino tends to lead to a moderately mild winter for the UK and NW Europe, probably due to the influence of the mean ridge.

However, this analysis masks considerable inter-month variability. Compare the temperature and 500 hPa height profiles for the three months:

Decembers tend to be about average, Januarys tend to be significantly below average with a very negative Arctic and North Atlantic Oscillation pattern, whilst Februarys tend to be on the mild side.

Now, turning to the possible impacts this winter, I would pick out the following:

1) The west North Pacific is anomalously warm which, if it continues into the next two months, will serve to maintain a strong Pacific High and east Pacific trough enhanced by the colder surface waters there - developing quite an amplified long wave pattern.

2) The colder SSTAs within the tropical Pacific and Atlantic will serve to strengthen the thermal gradient and increase the zonal and vector wind anomalies along the lines shown - strong sub-tropical jet likely to support greater pressure over Greenland and increase the chances of displaced polar jet flow.

3) The overall reanalysis points towards lower pressure in the central Atlantic which coincides with the colder SSTA there right now. The warmer anomalies are essentially to the north of this making it likely that the polar jet flow will be weaker than normal and for low pressure systems to take a progressively lower track. In effect, I see this as a clear signal for the current (-ve) North Atlantic Oscillation to be enhanced by the presence of a weak to moderate El Nino.

4) We are now at the low point of the solar flux .

We have also to recognise increasing global temperatures and the potential for an above average December to disrupt the build-up of cold continental air. The use of any comparisons must also reflect the massively polar temperature anomalies.

Given these I will follow the SSTA and October / November temperature outturn with great interest. If we observe a more traditional Autumn pattern and the north Atlantic warm anomalies stay as they are now, then I would suggest we could well be looking at an overall winter with some significant and often extreme weather conditions - both mild and cold.

GP

Just read your incredibly detailed post my friend and ALL i can say is FASCINATING!

Thank you

[VillagePlank]

El Nino has nothing at all to do with weather; in fact it's all spaceships. If you haven't figured that one out, then how do you explain the apparent SST correlation with the moon?