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BornFromTheVoid

Sea Surface Temperatures

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I think there was a thread a few months ago on SSTs, but I couldn't find it so mods, feel free to move this post if ye like.

Anyhow, it seems there's has been quite an increase in SSTs over the last 10 days or so over north west Europe, especially the British Isles, which has changed from negative to positive anomalies. I presume this was due to the recent warm spell we had coupled with the sunshine.

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The large negative anomaly over the Azores and positive anomaly around Greenland still persist as they have done for a few months now.

I can't say what impact this change or current North Atlantic SST anomalies will on our weather other than the obvious of making things very slightly milder around our coasts, so I'll leave the technical analysis to the more knowledgeable members!

Here are the anomalies from this time of year the last few years;

post-6901-12751293189059_thumb.gif post-6901-12751293391254_thumb.gif post-6901-12751293608272_thumb.gif post-6901-12751293881576_thumb.gif

Edited by NaDamantaSam

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I'd say there's three important things shown on the maps which will effect our weather over the coming months.

The North Atlantic SST Tripole idicates a -NAO and a mid Atlantic ridge for the summer. The rapidly developing La Nina reinforces the idea of high pressure blocks/mid Atlantic ridge. And the -PDO showing in the North Pacific will help to modertae temperatures in the NH.

So all together, solely based on SSTs, the forecast for the Summer would be for dry, generally settled weather with temperatures around average to slightly below.

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Not a good chart looking for warmth, negative AO/NAO signature prevelent for the next twenty days again at least in my opinion.

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Not too much change since the chart from the 28th. The positives anomalies around the British Isles have been reduced to roughly average, La Nina looks to have weakened a little but the same braod patterns don't seems to have changed all that much.

post-6901-12755731206094_thumb.gif post-6901-12755731282227_thumb.gif

Very impressive negative anomaly in the Okhotsk Sea.

I'd say there's three important things shown on the maps which will effect our weather over the coming months.

The North Atlantic SST Tripole idicates a -NAO and a mid Atlantic ridge for the summer. The rapidly developing La Nina reinforces the idea of high pressure blocks/mid Atlantic ridge. And the -PDO showing in the North Pacific will help to modertae temperatures in the NH.

So all together, solely based on SSTs, the forecast for the Summer would be for dry, generally settled weather with temperatures around average to slightly below.

Thanks for that. Could you explain what exactly the tripole is and how it results in a -NAO?

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The tripole is the banding of SSTs in the Atlantic with Warm anomalies below Greenland and between West Africa and the Carribean and cooler anomalies inbetween. This pattern of SSTs promotes a -NAO and was one of the factors that influenced the weather we had this Winter.

The warm anomalies favour high pressure and the cooler anomalies favour lower pressure. So the warm anomalies South of Greenland would favour a Greenland high/mid atlantic ridge and then lower pressure would be favoured over the Azores, i.e., -NAO. There's a diagram somewhere on the net that shows it quite nicely but I can't seem to find it at the moment, I'll post it later if I find it.

Of course this is just one factor and other's come into play when forming a full forecast. But purely looking at SSTs that is the pattern they are promoting.

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Thanks for that. I guess I was working off the assumption that sst anomalies and air pressure patterns worked the same as with landmasses, the way you get continental high pressure during winter because of the cooling and then slack low pressure in the summer.

I'm still unsure as to how the opposite occurs with sea surface temperature patterns, though I guess with sst it's a mixture of anomalies and absolutes.... confusing! Perhaps this is something I should pursue in the learners area...

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There's people on here more qualified than me to answer some of your questions. Hopefully someone might pop in and help you out. :)

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It seems there has been some slight changes in SST anomalies over the last week or 2. Temperature anomalies have really increased around the British Isles and the tripole appears to be even more clear and entrenched than it has been.

SSTs have warmed up across the N Pacific, especially around Japan, the Kamchatka peninsula and in parts of the central north Pacific, where things have switched from large negative anomalies to positive in just 2 weeks. Not sure if these changes in Pacific ssts are quite widespread enough to have much effect downstream but once more, I'll leave the analysis to more knowledgeable members!

post-6901-12764942633253_thumb.gif post-6901-12764943280526_thumb.gif post-6901-12764943536715_thumb.gif

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A quick update on ssts.

It seems a negative PDO pattern is appearing with a clear reverse "C" shape of negative anomalies now present in the North Pacific. The negative anomalies from the developing La Nina have spread almost as far as Papua New Guinea and is now connecting the a large cool anomaly just to the north.

Positive anomalies are still present around Japan, the Korean peninsula and the Kamchatka peninsula while much of the rest of the N Pacific remains relatively cool.

In the Atlantic, the large negative anomaly around the Azores has spread eastward into the western Mediterranean and waned just a little, while a positive anomaly is quickly forming to the south west of Ireland. Positive anomalies around sub equatorial waters in the Atlantic have eased a little, but warming in the Gulf of Mexico has increased which isn't good news, especially with the oil spill. The cool waters to the north east of Iceland have all but disappeared and we now have negative anomalies now all around Scandinavia and in the Baltic Sea.

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Could someone tell me what sst patterns you would expect to find with a negative AMO? Is it similar to the PDO or just generally cooler surface waters?

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The AMO is basically a reflection of sea surface temperature anomolies in the tropical Atlantic and is recording near record positive values at the moment.

What we see in the sea surface temperature anomoly pattern at the moment is a negative NAO pattern with a 2006 like twist in that the cold pool is weakening to the west of Spain and will therefore encourage the devlopment of a ridge displaced into western Europe, however with a strong signal for a mid-Atlantic ridge present as well, there is likely to be some potent switcharounds as we saw quite virolently in May.

In the longer term, the cold pool off the USA is likely to move eastward which will promote a strongly negative NAO pattern into Autumn.

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The AMO is basically a reflection of sea surface temperature anomolies in the tropical Atlantic and is recording near record positive values at the moment.

What we see in the sea surface temperature anomoly pattern at the moment is a negative NAO pattern with a 2006 like twist in that the cold pool is weakening to the west of Spain and will therefore encourage the devlopment of a ridge displaced into western Europe, however with a strong signal for a mid-Atlantic ridge present as well, there is likely to be some potent switcharounds as we saw quite virolently in May.

In the longer term, the cold pool off the USA is likely to move eastward which will promote a strongly negative NAO pattern into Autumn.

A blocked winter being favoured at present then?

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Yes, however there is a danger it could develop to the south, especially in the latter half or winter.

It really depends on whether the warm anomoly behind the cold anonomoly at present develops and tracks eastward over the Autumn.

Edited by summer blizzard

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Latest chart shows the main Jet track on a NW/SE trajectory which is what the models are now beggining to show (possibly progressive due to a 20 day lag on average), however sea surface temperature anomolies do not encourage a strong enougth pattern for cold zonality to take hold, instead making the Jet Stream hit a brick wall with a cut-off low over Europe and a cut-off high over the UK, so relatively seetled weather looks favoured as we go into mid July.

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http://weather.unisys.com/archive/sst/sst_anom_loop.gif

Very bad news!

The cold anomoly that was off the eastern USA has moved westward and is still maintaing strength, within the next month it will be situated right next to the UK. The response to this and the warm anomoly north of it will be a trough parked over the UK.

In conclusion, if September is not wetter than average, i will eat one of my fingers.

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http://weather.unisy...t_anom_loop.gif

Very bad news!

The cold anomoly that was off the eastern USA has moved westward and is still maintaing strength, within the next month it will be situated right next to the UK. The response to this and the warm anomoly north of it will be a trough parked over the UK.

In conclusion, if September is not wetter than average, i will eat one of my fingers.

slip there I think, for 'moved westward' read moved eastward?

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http://weather.unisys.com/archive/sst/sst_anom_loop.gif

Very bad news!

The cold anomoly that was off the eastern USA has moved westward and is still maintaing strength, within the next month it will be situated right next to the UK. The response to this and the warm anomoly north of it will be a trough parked over the UK.

In conclusion, if September is not wetter than average, i will eat one of my fingers.

Dunno if I would say it has maintained its strength SB. From these images from the last 2 weeks, it would appear it has gone from >3C below average to just over 1C below.

post-6901-054617800 1280058671_thumb.gif post-6901-062230700 1280058638_thumb.gif post-6901-062122000 1280058684_thumb.gif

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Dunno if I would say it has maintained its strength SB. From these images from the last 2 weeks, it would appear it has gone from >3C below average to just over 1C below.

post-6901-054617800 1280058671_thumb.gif post-6901-062230700 1280058638_thumb.gif post-6901-062122000 1280058684_thumb.gif

Fair enougth, it has lost some strength, however looking at the loop it is moving steadily towards the UK. In its current position it supports an Atlantic ridge, once it moves over the UK it will support a trough over/south of the UK.

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Fair enougth, it has lost some strength, however looking at the loop it is moving steadily towards the UK. In its current position it supports an Atlantic ridge, once it moves over the UK it will support a trough over/south of the UK.

Any chance you could give a basic outline on how you work out the effects that the positions of warm and cold sst anomalies have on weather SB? Most papers I've tried to read online tend to go over my head somewhat!

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Any chance you could give a basic outline on how you work out the effects that the positions of warm and cold sst anomalies have on weather SB? Most papers I've tried to read online tend to go over my head somewhat!

Its basically about warm and cold anomoly couplets, i will try illustrate a chart to show you.

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Its basically about warm and cold anomoly couplets, i will try illustrate a chart to show you.

As basic an explination as possible. The two most important things to remember when using sea surface temperature anomolies are the words convergance and divergance, because these are very important in regards to the thermal gradiant.

As you can see from the chart attached, in the Atlantic we currently have a tripole pattern in that we have warm/cold/warm going from the top downwards. Now think of the warm anomolies as promoting southerly winds and the cold anomolies as promoting northerlies. Now starting at the top of the chart because the Jet Stream will always try travel poleward, we have warm anomolies around and south of Greenland, promoting warm air advection (southerlies), and a cold anomoly beneath it, now if you put an up arrow on the warm anomoly and a down arrow on the cold anomoly beaneath it, you can see that they are in opposing directions and are therefore divergant meaning that the thermal gradiant is weak and that high pressure will likely develop in the area between them. Now, you can also see the warm anomoly beneath the cold one, now if you do the same arrow idea, you can see that the two arrows converge, this is where the greatest thermal gradiant will be and thus low pressure will be promoted, as you can see they indicate a mid-lattitude high to be present at the current time.

While you cannot pin point the exact weather with this method, you can gauge a pattern, the lag time for this being around 20 days, which does not bode well at all for August..

post-1806-048590000 1280094433_thumb.gif

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As basic an explination as possible. The two most important things to remember when using sea surface temperature anomolies are the words convergance and divergance, because these are very important in regards to the thermal gradiant.

As you can see from the chart attached, in the Atlantic we currently have a tripole pattern in that we have warm/cold/warm going from the top downwards. Now think of the warm anomolies as promoting southerly winds and the cold anomolies as promoting northerlies. Now starting at the top of the chart because the Jet Stream will always try travel poleward, we have warm anomolies around and south of Greenland, promoting warm air advection (southerlies), and a cold anomoly beneath it, now if you put an up arrow on the warm anomoly and a down arrow on the cold anomoly beaneath it, you can see that they are in opposing directions and are therefore divergant meaning that the thermal gradiant is weak and that high pressure will likely develop in the area between them. Now, you can also see the warm anomoly beneath the cold one, now if you do the same arrow idea, you can see that the two arrows converge, this is where the greatest thermal gradiant will be and thus low pressure will be promoted, as you can see they indicate a mid-lattitude high to be present at the current time.

While you cannot pin point the exact weather with this method, you can gauge a pattern, the lag time for this being around 20 days, which does not bode well at all for August..

Suppose that makes sense, though I can see how complicated it could get with anomalies of different strengths, sizes and shapes and then all the lag times and teleconnections interfering.

Thanks though SB :good:

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Suppose that makes sense, though I can see how complicated it could get with anomalies of different strengths, sizes and shapes and then all the lag times and teleconnections interfering.

Thanks though SB :wallbash:

Indeed, though ENSO is really the only teleconnection caused by sea temperature anomolies (but not at the surface, in regards to the MEI sub surface temperatures are of much more importance), the QBO on the other hand occurs before the lag effect on sea surface temperature anomolies (a -QBO means increased easterlies in the tropics which is why there is so much heat in the tropical Atlantic this year - it has been drawn from Africa).

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Signs pointing towards a cool and unsettled Autumn.

Also perhaps a chance of a decent storm or maybe an ex hurricane at some point.

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The cold pool that was moving towards us has all but disappeared at this stage with the North Atlantic looking very warm. SST anomalies around Greenland looking especially high. La Nina is still rapidly developing, with areas 4C below average beginning to appear.

post-6901-020924800 1280623573_thumb.gif

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