Met Office winter NAO forecast...

[summer blizzard]

As we all know, the Met Office winter NAO forecast is based upon sea surface temperature anomolies during May, the forecast after May 2005 was -1.1 and the forecast after May 2006 was 0.6, so i was curious to know where we stand on this...

[johnholmes]

no doubt we shall be told when all the May data is in, it is only 10 May at the moment!

[summer blizzard]

True, but when i get the time, i will post up the latest charts so we can compare them to previous years, though at the moment, were closer to 2005 than 2006.

[Gavin P]

Heres the anomoly charts for now in 2005, 2006 and 2007;

http://www.osdpd.noaa.gov/PSB/EPS/SST/data...t.5.10.2005.gif

http://www.osdpd.noaa.gov/PSB/EPS/SST/data...t.5.13.2006.gif

http://www.osdpd.noaa.gov/PSB/EPS/SST/data...t.5.10.2007.gif

As you can see 2005 is quite clearly a -NAO pattern, with definatle warm, cold, warm bands. 2006 is quite obviously a +NAO pattern, with no distinct cold band around newfoundland. 2007 looks to be somewhere in the middle at this point, but if I had to choose one side or the other, I would agree with SB that it looks closer to 2005 than 2006. At this stage though, with quite a bit of May to go, it could still go either way, I think.

[BLAST FROM THE PAST]

Keep your eyes peeled on the La Nina situation, its strength will be very important factor.

BFTP

[summer blizzard]

http://www.metoffice.gov.uk/research/seaso.../nao/index.html

This is a vital link, this has the chart for what is required for a positive NAO setup, so comparing the current chart to that one...

http://www.osdpd.noaa.gov/PSB/EPS/SST/data...t.5.10.2007.gif

The anomoly around Newfoundland is negative, favouring a negative NAO.

The anomoly in the eastern Atlantic is positive, favouring a negative NAO.

The anomoly to the south of Greenland is positive, favouring a negative NAO.

The anomoly to the east of Greenland is negative, favoring a negative NAO.

The anomoly over Europe is positive, favouring a positive NAO.

Keep your eyes peeled on the La Nina situation, its strength will be very important factor.

BFTP

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

That is true, some models have it verging on been a strong event, though my personal opinion is that it will peak at high weak La Nina intensity, with neautral conditions by winter.

[kold weather]

I'm not even sure it'll make it to La Nina if I'm honest, subsurface temps have leveled out to just over 0.0C, the eastern side has below average temps while the remains of el nino is still present in the western part of the Pacific and its balancing itself out right now. Still ENSO events are very hard to forecast in Spring.

[summer blizzard]

I'm not even sure it'll make it to La Nina if I'm honest, subsurface temps have leveled out to just over 0.0C, the eastern side has below average temps while the remains of el nino is still present in the western part of the Pacific and its balancing itself out right now. Still ENSO events are very hard to forecast in Spring.

I can see your point, the best and most recent anologue for March and April is 1991 in my opinion, after leveling off, El Nino reemerged, though we are slightly lower than 1991, and a repeat would probably see weak El Nino values for the rest of the year.

[Glacier Point]

http://www.metoffice.gov.uk/research/seaso.../nao/index.html

This is a vital link, this has the chart for what is required for a positive NAO setup, so comparing the current chart to that one...

http://www.osdpd.noaa.gov/PSB/EPS/SST/data...t.5.10.2007.gif

The anomoly around Newfoundland is negative, favouring a negative NAO.

The anomoly in the eastern Atlantic is positive, favouring a negative NAO.

The anomoly to the south of Greenland is positive, favouring a negative NAO.

The anomoly to the east of Greenland is negative, favoring a negative NAO.

The anomoly over Europe is positive, favouring a positive NAO.

I would tend to agree on a slightly -ve NAO projection based on both the current May plot and the March-May current plot as the UKMET also base their statistical analysis on this time frame.

This could of course mean nothing if the polar stratosphere cools once more and the NAO signal gets swamped by a +ve AO. An easterly Quasi Bienniel Oscillation should however help in this respect by negating to some extent any cooling events that might occur.

Edited May 12, 2007 by Glacier Point

[beng]

http://weather.unisys.com/archive/sst/sst_anom-070506.gif

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

I'm not sure if I agree with the comments regarding la nina waning. Certainly the pattern didn't really seem to get going during April - however in the last 10 days (and I've been checking the charts daily) the La Nina pattern is now showing good signs of developing. Have a look at the above 2 links and you'll see what I mean. Most of the forecasts I believe are for it to develop early Summer - and this IMO now seems to be happening.

Anyway I agree that the signal is there for a negative NAO based on the MO methodology - probably hard to say how negative.

What do people think of the state of the North Pacific though? Seems quite cool - presumably if this pattern is there into the winter, then the effect would be a weakened Pacific jet - and potentially a colder than normal winter for N America? This might also have implications for the NAO.

Would we be right in saying that the PDO signal is now entering the negative cycle? The last real negative cycle was from around 1947-75

http://www.srh.noaa.gov/abq/feature/PDO_NM.htm

If so then perhaps we can expect a slow down in the current level of warming.

[Gavin P]

Regarding La Nina, I agree. It looks to me as though the massive cold anomoly thats been down the Pacific Coast of the US is now heading towards the Equatorial regions of the Pacific. Definatly looks like La Nina is developing to me.

[summer blizzard]

http://weather.unisys.com/archive/sst/sst_anom-070506.gif

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

I'm not sure if I agree with the comments regarding la nina waning. Certainly the pattern didn't really seem to get going during April - however in the last 10 days (and I've been checking the charts daily) the La Nina pattern is now showing good signs of developing. Have a look at the above 2 links and you'll see what I mean. Most of the forecasts I believe are for it to develop early Summer - and this IMO now seems to be happening.

Anyway I agree that the signal is there for a negative NAO based on the MO methodology - probably hard to say how negative.

What do people think of the state of the North Pacific though? Seems quite cool - presumably if this pattern is there into the winter, then the effect would be a weakened Pacific jet - and potentially a colder than normal winter for N America? This might also have implications for the NAO.

Would we be right in saying that the PDO signal is now entering the negative cycle? The last real negative cycle was from around 1947-75

http://www.srh.noaa.gov/abq/feature/PDO_NM.htm

If so then perhaps we can expect a slow down in the current level of warming.

I would say the current anomolies would mean a value of around -0.5.

Unfortunately, we had nearly the same pattern in the Pacific last year, so plenty of time for things to change, though it would indicate an amplified Pacific Jet Stream if things held.

It is possible that we are now entering a negative PDO cycle, if you plot the data for the past thirty years, you can see a tendancy towards a more negative PDO especially in the last ten years, suprisingly, if you do the same thing for the AO over the last thirty years, you see a fairly high correlation between the two.

Since June, we have observed PDO values of no more than 1 either side, the ast time we had a run of nine neutral months was June 2004 to February 2005, though this run began in May 2003, though on average, we are observing values around 0.5 and 1 lower than the first nine months of that cycle.

Based on this, i am going to make a little prediction for each month of the rest of this year and the winter months of 2008...

April: Neutral to negative PDO

May: Neutral to negative PDO

June: Neutral to negative PDO

July: Neutral to positive PDO

August: Neutral to negative PDO

September: Neutral to negative PDO

October: Neutral to positive PDO

November: Neutral to positive PDO

December: Neutral to negative PDO

January: Negative PDO

February: Neutral to negative PDO

Unfortuanely, with the PDO set to be near neutral for the remainder of this year, and the ENSO also neautral at the moment, this means that the QBO and AO are the major players at the moment, though to me, both look favourable for next winter.

[Lettucing Gutted]

I'm not even sure it'll make it to La Nina if I'm honest, subsurface temps have leveled out to just over 0.0C, the eastern side has below average temps while the remains of el nino is still present in the western part of the Pacific and its balancing itself out right now. Still ENSO events are very hard to forecast in Spring.

Another El Nino? Oh no! Not again...

[Guest Viking141]

Do we know when this forecast is due out?

[disco-barry]

Can i just say let's just wait until the winter is abit nearer, no offence but 99% of these forecasts we get throughout the year from everybody are wrong.

[kold weather]

Beng- The surface temps are a little cooler over the last 10-20 days though SOI still looks like a neutral set-up to me rather then La Nina and while the eastern section of the Pacific does much colder then it did last month, subsurface temp profiles still show a stubborn warmer patch in the areas that count in terms of upgrading, the 3+4 section. Eastern section shows quite a large pooling of colder waters which does sort of indicate that something will deelop over the next 30-90 days.

I suspect we will see La nina come August given the way the SST's are developing in the eastern side looks like it'll eventually spill further westwards IMO. Rainfall patterns globally also seem to suggest La nina as well...as a hurricane watcher I suppose a La nina would be intresting for an active season.

Also Beng, its intresting you point out that cooler mass in the north, it seems to have been present in one form or another for a good 7-10 years, I believe its a KEY reason why our winter temps have taken a surge upward since 1997, esp El nino years, because the thermal gradient is increased, i suspect it must be somethnig to do with cycles though goodness knows what one!

Edited May 17, 2007 by kold weather

[Don]

Do we know when this forecast is due out?

The Met Office Winter NAO forecast is normally out around mid June I think.

[beng]

Thanks Kold - totally agree we're not in La Nina yet, but i think it's coming - although as you say it may take a few more months.

Just been reading up a bit recently on the pacific patterns in response to the large negative anomaly there - the following links are quite interesting:

http://science.nasa.gov/headlines/y2000/ast15sep_1.htm

http://www.ispe.arizona.edu/climas/learn/pdo/index.html

http://www.srh.noaa.gov/abq/feature/PDO_NM.htm

I think the anomaly there relates to the PDO cycle - and it does appear we may be entering a negative phase of this cycle before too long. Indeed one of the above articles backs up what you said by mentioning that the positive phase of the PDO tends to enhance El Nino winters and suppress La Nina winters.

Actually looking at today's SSTs

http://weather.unisys.com/surface/sst_anom.html - you can almost see the horseshoe shape characteristic of a negative PDO.

Ben

Edited May 17, 2007 by beng

[summer blizzard]

Thanks Kold - totally agree we're not in La Nina yet, but i think it's coming - although as you say it may take a few more months.

Just been reading up a bit recently on the pacific patterns in response to the large negative anomaly there - the following links are quite interesting:

http://science.nasa.gov/headlines/y2000/ast15sep_1.htm

http://www.ispe.arizona.edu/climas/learn/pdo/index.html

http://www.srh.noaa.gov/abq/feature/PDO_NM.htm

I think the anomaly there relates to the PDO cycle - and it does appear we may be entering a negative phase of this cycle before too long. Indeed one of the above articles backs up what you said by mentioning that the positive phase of the PDO tends to enhance El Nino winters and suppress La Nina winters.

Actually looking at today's SSTs

http://weather.unisys.com/surface/sst_anom.html - you can almost see the horseshoe shape characteristic of a negative PDO.

Ben

I'll read those links later, but you are right in that we are moving into a negative PDO cycle, which corelates perfectly on a chart with the AO as we are moving into a negative AO cycle as well.

Yes, right now we have the high lattitude cold anomolies and the cold anomolies west of the USA, though we are lacking the warm anomoly in the western mid-lattitude Pacific, which is why we are recording only neutral values.

[Lettucing Gutted]

though we are lacking the warm anomoly in the western mid-lattitude Pacific, which is why we are recording only neutral values.

It's ironic isn't it? It is so warm in Britain because there isn't a warm anomaly in the western temperate North Pacific Ocean.

Edited May 17, 2007 by Craig Evans

[beng]

It's ironic isn't it? It is so warm in Britain because there isn't a warm anomaly in the western temperate North Pacific Ocean.

LOL yes - however there's more to the UK climate than the PDO - I don't think it's done us many favours (considering the global climate warming trend) in terms of cold winters in recent years though.

[BLAST FROM THE PAST]

I'm anticipating La Nina to strengthen over the next two months with a 'generally' wettish Aug, wet Sept, Oct, Nov...opposite pattern to last year...bar August.

BFTP

[summer blizzard]

I am also expecting La Nina to strengthen, though not reaching weak values until August or September and peaking between -0.9 and -1.1, with a weak La Nina winter.

[NorthYorksWeather]

I would say the current anomolies would mean a value of around -0.5.

Unfortunately, we had nearly the same pattern in the Pacific last year, so plenty of time for things to change, though it would indicate an amplified Pacific Jet Stream if things held.

It is possible that we are now entering a negative PDO cycle, if you plot the data for the past thirty years, you can see a tendancy towards a more negative PDO especially in the last ten years, suprisingly, if you do the same thing for the AO over the last thirty years, you see a fairly high correlation between the two.

Since June, we have observed PDO values of no more than 1 either side, the ast time we had a run of nine neutral months was June 2004 to February 2005, though this run began in May 2003, though on average, we are observing values around 0.5 and 1 lower than the first nine months of that cycle.

Based on this, i am going to make a little prediction for each month of the rest of this year and the winter months of 2008...

April: Neutral to negative PDO

May: Neutral to negative PDO

June: Neutral to negative PDO

July: Neutral to positive PDO

August: Neutral to negative PDO

September: Neutral to negative PDO

October: Neutral to positive PDO

November: Neutral to positive PDO

December: Neutral to negative PDO

January: Negative PDO

February: Neutral to negative PDO

Unfortuanely, with the PDO set to be near neutral for the remainder of this year, and the ENSO also neautral at the moment, this means that the QBO and AO are the major players at the moment, though to me, both look favourable for next winter.

could you plz tell me how the PDO effects our winters? thanks

[summer blizzard]

The PDO (Pacific Decadel occilation) has a large infuence on our weather, when not at neutral values, it esentially dictates the state of the PNA with a 70% correlation between the two and also to a lesser degree the AO, with a 30% correlation, this is a positive correlation, meaning that if the PDO is negative then the PNA will be encouraged to be negative as well rather than a negative correlation which would mean that the PNA would be encouraged to go positive.

A negative PDO will typically see the following anomoly patttern on a sea surface temperature anomoly chart...

http://jisao.washington.edu/pdo/

As you can see, a negative PDO would typically favour a split Pacific Jet Stream and Alaskan Trough.

As well as having another positive correlation with the ENSO state, it can aid in the development or hindrance of developing ENSO events.

Seen as though i am expecting near neutral conditions and La Nina looks only to be a weak affair, giving only a slight bias towards a negative PNA and AO, i think that the QBO will be the most important teleconnection this winter, giving a fairly large bias towards a negative AO.