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The cold pool seems to have weakened a tad to my eye and one musn't forget the positive anomalies in the western Atlantic and Davis Strait

Indeed, the positive spike of the eastern seaboard is significant now. Will be interesting to see how that develops though would have thought the Atlantic cold pool is still cold and widespread enough to probably affect us somewhat if winds come from the west/northwest for the rest of Autumn at least. 

 

If things get too active in the Atlantic with lots of depressions it is not often a great sign imo. Often, I find colder air struggles to get pulled down when the Atlantic is active because as cold air tries to come down the west side of one depression, another developing depression drags warmer air up hence any cold enough bursts for wintry ppn are weak and very short if at all.

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CDF...

 

Reading your post above, I realised that last winter we had a lot of North-West winds, mainly coming down from Greenland and Iceland.

However the temperatures in the eastern Atlantic were not too cold at that stage, so the precipitation that fell was rain/sleet rather than snow..

 

As I understand it the cold anomaly was present last winter, but as a much smaller area south of Greenland, and  cyclogenisis seemed to form depressions on the left hand edge of the colder waters before moving up to the Icelend area and then plunging down over the UK. 

 

The colder sst's  seems to have expanded now and includes the Atlantic just west of Ireland. It certainly will be interesting to see how these depressions move this year. It could be that the depressions will form further east also, in the eastern Atlantic and then it could be a thoroughly wet and miserable winter with the temperatures fluctuating wildly, Or if they form in the western Atlantic, as per last year, then it could get very interesting with a lot of snow.

 

However the El Nino effect could send one depression after another barrelling across the Atlantic with rapid deepening and we all know what that means!!

 

All in all an interesting period ahead, and that is without considering any blocking anticylones which may be caused by the cooler waters, possibly causing a very cold winter for us.

 

It seems like the pattern has set up an almost infinite number of options are perfectly possible (even more so than usual).

 

The two drivers (El Nino and abnormally low sst's in the North Atlantic) are not a usual set of conditions (in measurable history) and we will have to see which affects us the most.

 

MIA

 

When you look at the NIno years, SST anomalies for winter and summer, the composite shows negative anomalies in the Atlantic for both seasons.

 

Summer  j7NcUPr.gif  winter  Hf7imvp.gif

 

http://www.esrl.noaa.gov/psd/enso/compare/

 

There is a one year animation on the environment Canada site - it's a constantly evolving picture but the warm Pacific, cold Atlantic theme is maintained. While Nino is strengthening, maybe signs the other strong 'blobs' in both oceans are moderating.

 

http://weather.gc.ca/saisons/animation_e.html?id=year&bc=sea

Edited by Nouska
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No I'm not saying that but it needs to be qualified. Cyclogenesis iis an umbrella term that covers more than one process. If you are using it in it's primary definition, that of depression development, then I would say, put very simply, that the main components were the poleward movement of warm air and the eastward movement of cold air.

 

But if you are talking rapid cyclogenesis along the eastern seaboard of the US then yes sea temps can play a vital role. This mainly applies in winter in association with major baroclinic zones and close to strong gradients of SSTs.

 

But what I have a problem with is generalised statements linking one process to a definitive statement such as downstream blocking when there are many other factors to be considered.

I agree that there are many factors involved but you know full well that I did not make any definitive statements at all. Read my post again and you will see that I refer to probabilities - not definitives.
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One thing I have noticed when the super cold winters have occurred, are the big areas of high pressure normally over the UK or Scandinavia 2 weeks or so before the main event.

I'm not sure the SST's will have that much of a knock on effect locally. As far as the Atlantic is concerned, the colder the better. The North Sea warmth however is useful for the snow making machine effect. 2010 December being a good example.

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When you look at the NIno years, SST anomalies for winter and summer, the composite shows negative anomalies in the Atlantic for both seasons.

 

Summer  j7NcUPr.gif  winter  Hf7imvp.gif

 

http://www.esrl.noaa.gov/psd/enso/compare/

 

There is a one year animation on the environment Canada site - it's a constantly evolving picture but the warm Pacific, cold Atlantic theme is maintained. While Nino is strengthening, maybe signs the other strong 'blobs' in both oceans are moderating.

 

http://weather.gc.ca/saisons/animation_e.html?id=year&bc=sea

 

Nouska

 

Thanks for the links..

 

Seems to also show  correlation with high pressure in Scandinavia and Northern Russia and low pressure to our west and southwest right across the Atlantic!

 

Could still mean anything as perhaps a hundred miles either way could, as always, give a dramatically different outcome for the UK .

 

Really interesting winter coming up I think!

 

MIA

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Here's an animation of North Atlantic SSTs over the last 8 weeks (using a 7 day average).

 

 

 

If we take the July SSTs for the region of 45-60N and 14-45W (shown in the red box), we get the following time series graph.

 

 

 

Clearly the coolest SSTs in that region on record.

 

 

Now, lets look at how the following Autumns went for all years under 13.25C on the graph.

 

September SLP Anomaly ..................... Sept SLP Anom With Extra Weigting to years under 13C

 

 

So no strong signal over the British Isles, other than for high pressure to our west for September.

 

 

October SLP Anomaly ..................... Oct SLP Anom With Extra Weigting to years under 13C

 

 

A clear signal for high pressure stretching from the Barents sea, across Scandi and over the British Isles.

 

November SLP Anomaly ..................... Nov SLP Anom With Extra Weigting to years under 13C

 

 

A very strong signal for low pressure over the Atlantic there, with a weak high over Europe.

 

So a mixed, northerly September. A more settled October, and an unsettled southerly/south westerly November.

 

Of course the above composites are assuming that the SST anomalies from the years used continue similar to this year during Autumn, which is far from guaranteed. Other factors coul be thrown into the mix too, such as ENSO, Solar activity, sea ice coverage, QBO, etc. I might try work some of them into the composites later on.

a very interesting post there, I wonder if the raw Met O model, in a week or so time may go along with this. It might just be another part of the not yet really understood building blocks for seasonal forecasting.

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Here's an animation of North Atlantic SSTs over the last 8 weeks (using a 7 day average).

 

XJVK4Ye.gif

 

If we take the July SSTs for the region of 45-60N and 14-45W (shown in the red box), we get the following time series graph.

 

BCvbwIn.png NwEQc8q.png

 

Clearly the coolest SSTs in that region on record.

 

 

Now, lets look at how the following Autumns went for all years under 13.25C on the graph.

 

September SLP Anomaly ..................... Sept SLP Anom With Extra Weigting to years under 13C

BuxrvKZ.pngQVpNHrl.png

 

So no strong signal over the British Isles, other than for high pressure to our west for September.

 

 

October SLP Anomaly ..................... Oct SLP Anom With Extra Weigting to years under 13C

XGjVkxX.pngcdB2imX.png

 

A clear signal for high pressure stretching from the Barents sea, across Scandi and over the British Isles.

 

November SLP Anomaly ..................... Nov SLP Anom With Extra Weigting to years under 13C

UsqyGwV.png 9WRFMyq.png

 

A very strong signal for low pressure over the Atlantic there, with a weak high over Europe.

 

So a mixed, northerly September. A more settled October, and an unsettled southerly/south westerly November.

 

Of course the above composites are assuming that the SST anomalies from the years used continue similar to this year during Autumn, which is far from guaranteed. Other factors coul be thrown into the mix too, such as ENSO, Solar activity, sea ice coverage, QBO, etc. I might try work some of them into the composites later on.

Fantastic post and very intriguing. I hope this bears fruit as I personally love dry (preferably warm) Octobers. Unsettled November's, especially with a southerly tracking jet, bode well for a cold winter to follow.
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What effect is the cold N Atlantic water having on the hurricanes starting up, and how long might the hurricane season last if the water remains cold?

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^^ That sounds not too different from 2009 to be honest, save for the northerly aspect in September.

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What effect is the cold N Atlantic water having on the hurricanes starting up, and how long might the hurricane season last if the water remains cold?

As hurricanes tend to initiate in tropical waters, probably none at all, WM... :)

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Is it cooler waters or warmer waters that help promote the building of high pressure?

Bearing in mind other factors.

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I don't think there really is any correlation yes NW'lies over stubborn chilly SST's in North Atlantic would result in less marginal situations. Last winter could have been a lot snowier if currents SST were in place. I fear a very wet Autumn is on the way - hopefully this gives way to a winter to remember not for the wrong reasons!

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Is it cooler waters or warmer waters that help promote the building of high pressure?

Bearing in mind other factors.

 

It's all about the couplet i believe. Cold over warm like we have now should produce convergence and a cyclonic downstream pattern. Warm over cold should produce divergence and a anti-cyclonic downstream pattern. 

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I know where hurricanes start, but sometimes (ie last summer, Bertha) we get hit by the tail end of them after they have been round the whole loop. Is that more or less likely this year with a cold N Atlantic?

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I know where hurricanes start, but sometimes (ie last summer, Bertha) we get hit by the tail end of them after they have been round the whole loop. Is that more or less likely this year with a cold N Atlantic?

 

Won't make a difference. Such anomalies may effect seasonal patterns but with hurricanes its about the day to day. 

 

I suppose theoretically a stronger jet stream would be more likely to catch and draw north a hurricane. 

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I know where hurricanes start, but sometimes (ie last summer, Bertha) we get hit by the tail end of them after they have been round the whole loop. Is that more or less likely this year with a cold N Atlantic?

Ah, now I understand what you are asking...And tbh, other than 'thinking' that cooler waters would help kill them off, I really don't know. But cold SSTs might aid the development of North Atlantic depression, in some way; and , TBH, I don't know the answer to that, either...Does anyone? :)

 

PS: Sorry WM, for seeming to be a bit patronizing. I didn't mean to come across that way. :)

Edited by Ed Stone
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Ah, now I understand what you are asking...And tbh, other than 'thinking' that cooler waters would help kill them off, I really don't know. But cold SSTs might aid the development of North Atlantic depression, in some way; and , TBH, I don't know the answer to that, either...Does anyone? :)

That's correct.

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Ah, now I understand what you are asking...And tbh, other than 'thinking' that cooler waters would help kill them off, I really don't know. But cold SSTs might aid the development of North Atlantic depression, in some way; and , TBH, I don't know the answer to that, either...Does anyone? :)

 

PS: Sorry WM, for seeming to be a bit patronizing. I didn't mean to come across that way. :)

Seems there's plenty to kill them off before they even get to cooler waters.

 

Julia Slingo said this about the cool Atlantic....

 

 

Closer to home the North Atlantic is more than 2 degrees colder than normal. It seems quite likely that the unusually cold North Atlantic has strengthened and pushed our jet stream south, also contributing to the low pressure systems that have dominated our weather.

http://blog.metoffice.gov.uk/2015/08/28/so-what-happened-to-our-summer/

 

My question, will the same apply autumn and winter?

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The jetstream shift was before the Atlantic cold anomaly, so is it in response to the Jetstream shift and now strengthening that position

 

 

BFTP

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The jetstream shift was before the Atlantic cold anomaly, so is it in response to the Jetstream shift and now strengthening that position

 

 

BFTP

Eh?

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What do you mean 'eh?'  Ed

 

quote - Closer to home the North Atlantic is more than 2 degrees colder than normal. It seems quite likely that the unusually cold North Atlantic has strengthened and pushed our jet stream south, also contributing to the low pressure systems that have dominated our weather

 

 

I can see I'm gonna enjoy your posts this autumn/winter......not

Edited by BLAST FROM THE PAST
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There's a relevant article that was first published in May earlier this year that suggests the Atlantic is entering a cool period with implications for the World's weather. Here are some snippets of interest from the report:

  • The Atlantic Ocean’s surface temperature swings between warm and cold phases every few decades and this so-called “Atlantic Multidecadal Oscillation†(AMO) can alter weather patterns throughout the world.
  • In the UK it would offer a brief respite from the rise of global temperatures.
  • When the AMO is in the warm phase, there are more hurricanes in the Atlantic. A cold Atlantic means fewer hurricanes hitting the southern US.
  • The mean temperature of islands downwind of the Atlantic such as Britain and Ireland show almost exactly the same temperature fluctuations as the AMO.
  • By comparing our sea-level index against the AMO index we were able to provide, for the first time, observational evidence of the widely hypothesised link between ocean circulation and the AMO. The observations that we do have of the Atlantic overturning circulation over the past ten years show that it is declining. As a result, we expect the AMO is moving to a negative (colder surfer waters) phase. This is consistent with observations of temperature in the North Atlantic.
 

Full article: http://theconversation.com/the-atlantic-is-entering-a-cool-phase-that-will-change-the-worlds-weather-42497

 

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Eh?

What BFTP is saying is that he is of the opinion that the jet stream has been tracking south far more often since about 2007/2008. He also raises the question as to whether this sinking of the jet has contributed to those low sst's in the atlantic. On a personal level, I would like to add to the mix the question of the strength of the gulf stream. There has been much talk over the last 8 years or so about the possible weakening of the gulf stream due to increased arctic sea melt. Do the low sst's in the atlantic add credence to this theory I wonder?

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What do you mean 'eh?'  Ed

 

quote - Closer to home the North Atlantic is more than 2 degrees colder than normal. It seems quite likely that the unusually cold North Atlantic has strengthened and pushed our jet stream south, also contributing to the low pressure systems that have dominated our weather

 

 

I can see I'm gonna enjoy your posts this autumn/winter......not

Why 'quite likely'? Why push it south? Why not north? An Atlantic-based anticyclone could push the jet-stream north just as it could push it south??

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