Sea Surface Temperature And Sea Ice Trends(2)

[WhiteFox]

But I'm not sure this totally explains everything that's going on right now. The cold anomalies down the western Atlantic are possibly a result of the cold winter there,

Not a cold winter towards the Eastern US GP; very mild first half for the North East was offset by a colder than average second half. Not sure this would account for such negative anomalies. Spring was a bit below average in the North East so maybe the waters haven't warmed as much as they usually do.

Hi GP, I wish i could remember what a met said to me a couple of weeks ago, but the Sw Atlantic anomalies are the result of a persistant synotpic set-up that has occured in the Spring, if I remember rightly it was something to do with an upper low being sat in a certain place and so we are seeing a certain amount of upwelling occur there, I wish I could remember exactly what it was!

The Bermuda High was displaced Westward for a large portion of April and May so this may have led to an Upper Level low in an unusual place during the same period?

Edited June 14, 2007 by WhiteFox

[summer blizzard]

I think that the lag is actually a resonable theory, as the effects are first felt under the surface, and there is a lag time of around six months for the sub-surface waters to rise, it is plausable that we are still seeing the effects of the El Nino, and given that we did not lose the El Nino until February, we should see continued cooling until sometime in August, there after it is likely that we will not see much cooling or warming until at least winter given a neautral pattern, because of this, i would say that sea surface temperatures are more favourable for a cooler Autumn and winter than at any time in the last five years.

[Glacier Point]

Some serious doubts about any development of La Nina if the current SSTA is to be taken at face value....

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

[BLAST FROM THE PAST]

Some serious doubts about any development of La Nina if the current SSTA is to be taken at face value....

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

GP

Yes Ien watching the weakening of it too, sems quite stark. Also eastern seaboard seems to strengthen wth cold anomay again.

BFTP

[Gavin P]

Doesn't the cold anomoly often weaken in 1 & 2 Regions and then reappear in 3 & 3.4 Regions a week or two later?

Certainly if we don't see a significant loweing of temps in 3.4 Region, within the next two or three weeks, then I would say La Nina will fail to arrive yet again.

Edited June 18, 2007 by Gavin P

[kold weather]

Very interesting to see the La Nina signal decay a little. the SOI did last week rise which is more typical of a La Nina pattern and I had wondered whether this was a sign of La nina finally taking the bull by the horns...however the weakening of the La nina signal i suppose does make sense given the whole Spring the pattern has been like el nino out in the Pacific, its hardly surprising that the La Nina has relaly had a hard time developing. The other issue is that we have just gone past the ebst time for La Nina to develop, if it doesn't get going now it probably won't do so til lthe Autumn/winter, if at all.

[summer blizzard]

Typically, La Nino events develop between November and May, while El Nino is May and November, so yes, i would be pretty confident that La Nina will no longer develop, at the same time, if we were looking at an El Nino of similar strength to 2006, i am sure we would of seen a much bigger rise in the MEI value, at worst, i would say we are looking at weak El Nino values from August-December, however i would favour neutral values.

Intersestingly, should sea surface temperature anomolies dominate the weather during the summer, they currently favour a very supressed Jet Stream over Aisa, the Pacific and the USA, however the pattern in the Atlantic is much more amplified, favouring an Azores Low and height rises over western Europe, around the 10th July, though with the QBO favouring height rises over Greenland, this could be a case of a southerly plume followed by retrogression and a northerly.

[Stu_London]

Still warm anomolies around the UK particularly to the east.

The weather this week may blow some of the warmth away and with low pressure to the east of the UK some upwelling may occur to flatten out the anomolies in the North Sea.

Much less anomolous warmth to the west and north of the UK with the cold anomoly in the mid atlantic creeping a bit closer.

[Iceberg]

La Nina is looking increasingly weak, tbh my gut instinct is suggesting a weak El Nino by Christmas

Last May and currently.

Edited June 26, 2007 by Iceberg

[BrickFielder]

Large scale sea surface temperature anomalies don't have much to do with the temperature of the air above. These are caused by the winds over the area of sea called trade winds. If you think of a pint of beer with a head on then the beer would represent cold deeper water and the frothy head warmer water heated by the air above. If you blow across the top of your beer the the froth will pile up on one side of the glass and the beer will be exposed on the other.

To track whether el nino or la nina will intensify then you need to look at the winds across the region and a good indicator of this is the SOI. If it is negative then we are tending towards el nino conditions if it is positive then we are tending towards la nina. SOI at the moment has swung positive but looks to be swinging back negative.

SOI and El nino explained

SOI values

MJO events play a part in reversing trade winds so any strong event tends to swing the SOI negative towards el nino. The other thing that plays a part is the Indian Monsoon which looks to be quite early this year showing up as a outgoing longwave radiation anolmaly. This is likely to drive the world weather patterns for the next month or so tending to overide any blocked pattern as it begins its migration.

Closer to home the cold pool of the united states coast is due to a steady uninterupted blow of winds across the Atlantic due in part to the displacement of the azores/bermuda high and partly due to the late break down of the winter stratospheric vortex which drove an atlantic pattern almost into summer(This in turn was due to the westerly QBO).

As winds have an affect on the sea, so does the sea have an affect on winds. The exact response depends on whether you have a baroclinic or barotropic reponse due to the season, but typically cold anomalies during winter promote westerly winds and warm anomalies promote easterly. It is extremely complicated what the response will be typically during summer the response to warmth is higher pressure at low levels, however the winter response would tend towards the response in the following diagram.

This of course can be overiden by stronger signals like the monsoon , a strong stratospheric vortex which is often combined with a westerly QBO. What we should be looking at closely at this time of year is land temperatures and soil moisture because land is likely to warm up much more during the summer than the sea and the barotropic response to this heating will be high pressure building over land with dry hot air. This is why the bermuda high has visited the southern states during april and may and in part this is driven by la nina. The fact that Europe is still damp from the late end to winter patterns only reinforces the pattern.

We should also pay attention to the fact that the hurricane season should start soon. which is likely to throw some energy into the pot most likely across the southern states where high presure will provide an avenue of reduced shear for them, with perhaps a wet season in the plains.

For us in the UK then we need to wait for high pressure to build across the continent for a settled period of warm weather and even then it is likely to be disrupted by movement of the asian monsoon. The earliness of the monsoon might be a harbinger of an early autumn but I rather think not and as for the winter then the easterly QBO will allow stratospheric warmings leading to a negative AO however expect that cold will build up quickly and the vortex will just be too strong for any blocking to really take hold. This I think increases the risk of a heavy snowfall from the north during winter.

[kold weather]

Do you really think we could have El nino Iceberg by xmas, I must say I'd be a touch surprised if this was the case. The SSTA are similar to last year but the global set-up is very different as BrickFielder has already pointed out. 2006 already had a negative SOI by July and it became more noticeable later in the summer, this June is finally seeing positive SOI values and i suspect we'll average weakly positive for the summer. Also the subsurface temps overall in the basin still do suggest something a touch below average for the next 2-4 months but not enough for La Nina. After that and no real signs of any major subsurface anomalies right now...all of which indicate neutral condtions IMO for the rest of the year.

[summer blizzard]

My personal opinion is that we will see ESNO neutral conditions from now until November, with a 20% chance of an El Nino and 80% chance of ENSO neutral conditions.

Anomolies still favour a trough to the south west in around 20 days time.

[Gavin P]

Met Office is forecasting a medium to strong La Nina this summer. Don't write it off yet.

Edited June 26, 2007 by Gavin P

[Iceberg]

Taken from the CPC update

"SEA SURFACE TEMPERATURES (SSTS) ALONG THE EQUATOR ARE CURRENTLY SLIGHTLY ABOVE NORMAL IN THE CENTRAL AND WESTERN PACIFIC OCEAN... AND BELOW NORMAL IN THE EASTERN PACIFIC. SSTS IN THE NINO 3.4 REGION OF THE EAST CENTRAL PACIFIC OCEAN (THE MEAN TEMPERATURE FROM 5N TO 5S AND 170W TO 120W) GIVE A GOOD INDICATION OF THE STRENGTH OF EL NINO (WARM SSTS) OR LA NINA (COLD SSTS). SSTS IN THE NINO 3.4 REGION ARE CURRENTLY CLOSE TO THEIR LONG TERM AVERAGE SUGGESTING ENSO IS NEUTRAL. EARLY IN THE YEAR A RAPID DECREASE IN NINO 3.4 SST ANOMALIES... THE DEVELOPMENT OF BELOW NORMAL SSTS NEAR THE EQUATOR ALONG THE SOUTH AMERICAN COAST... AND DYNAMICAL MODEL PREDICTIONS OF PACIFIC SSTS RAISED CONCERNS ABOUT A TRANSITION TO LA NINA CONDITIONS BY MID 2007. HOWEVER... BELOW NORMAL SSTS HAVE NOT DEVELOPED IN THE CENTRAL PACIFIC... AND SUB-SURFACE OCEAN TEMPERATURES IN THE CENTRAL PACIFIC HAVE RECENTLY BECOME SLIGHTLY ABOVE NORMAL. THESE INDICATORS MAKE A TRANSITION TO LA NINA CONDITIONS MUCH LESS LIKELY IN THE NEXT FEW MONTH THAN HAD APPEARED EARLIER IN THE YEAR. MOST DYNAMIC MODELS CONTINUE TO PREDICT A TRANSITION TO LA NINA CONDITIONS BY LATE SUMMER... ALTHOUGH STATISTICAL MODELS PREDICT THAT CENTRAL PACIFIC SSTS WILL DRIFT ONLY SLIGHTLY DOWNWARD... INDICATING NEUTRAL ENSO OR ONLY VERY WEAK LA NINA CONDITIONS. THUS... AT THIS TIME NEUTRAL ENSO CONDITIONS ARE ANTICIPATED THROUGH JAS WITH THE DEVELOPMENT OF LA NINA CONDITIONS POSSIBLE LATER IN THE FALL... ALTHOUGH AT THIS TIME IT APPEARS THAT LA NINA CONDITIONS WILL BE WEAK. THUS ENSO HAS A LIMITED IMPACT ON THIS SERIES OF FORECASTS. "

IMO the above is the CPC hedging there bets, The chances of a La Nina are rapidly receding, it's only by personal leaning, but I think one of the effects of AGW (please don't discuss it here !) is that neutral Enso conditions which would have occured historically will now have the effect of Weak El Nino's on Global Weather Patterns, There is something of a postive reinforcement mechanism here and by Christmas we could be in a weak El Nino in real terms.

However I stress could and weak. Probabilities indicate a continuing neutral ENSO.

Matt

[beng]

http://www.bom.gov.au/climate/enso/

Fresh update today from Australia seems pretty bullish about la nina developing.

[Glacier Point]

Upper level zonal winds have also increased in the last 10 days over the equatorial Pacific where previoulsy they were just about the only area not showing an increase in -ve zonal winds anomalies.

All of this should translate to a final slide into weak La Nina by August I think. Either way, no major impact from ENSO on the Atlantic pattern which continues to indicate some sort of weakness likely to develop around the Azores / eastern Atlantic into August.

[Gavin P]

Does that mean an unsettled August?

[Glacier Point]

Does that mean an unsettled August?

quite the reverse

[BLAST FROM THE PAST]

Sounds like something akin to August 2004 to me. Low pressure down to the south west and troughs swinging north bringing heavy thundery rain/showers from Biscay area

Edit...I could be wrong though!

Tamara

Humid but thoroughly wet!!!

BFTP

[Gavin P]

Well, I'm not really great at all this teleconnections buisness, but as far as SST's go, my view is that the situation that in the Atlantic/Pacific that helped produce this horrendous June isn't showing signs of chaning anytime soon, so personally, I'm not really expecting much of an upturn in the weather (certainly not an extended one) anytime in the near future.

[summer blizzard]

Upper level zonal winds have also increased in the last 10 days over the equatorial Pacific where previoulsy they were just about the only area not showing an increase in -ve zonal winds anomalies.

All of this should translate to a final slide into weak La Nina by August I think. Either way, no major impact from ENSO on the Atlantic pattern which continues to indicate some sort of weakness likely to develop around the Azores / eastern Atlantic into August.

The wakness over the Azores should encourage high pressure to form over western Europe however sea surface temperature anomolies have indicated this senario for some time and it is reliant on a positive PNA forming without being over ruled by the QBO signal.

[summer blizzard]

[kold weather]

I'd have a really hard time trying to forecast the ENSO state for the next 3-6 months if I had to. In real time sits not gonig to make much difference here unless it gets above weak which I'll be pretty surprised if it does, esp if it reaches strong...if only for long term climate reasons, its just not supported right now.

In terms of the Atlantic SSt's, as summer said it does sort of supportan Azores low to be rpesent weakly however i think the current signal also support a -ve NAO which combined with the current QBO I think its helping to over-ride the signal to a certain extent, the LP has been slightly displaced over NE Europe instead with the heat also displaced further SE in response.

[summer blizzard]

Those are some good points Kold, also unlike last year when anomolies favoured an Azores Low, we dont have warm anomolies in the western Atlantic, therefore the Jet Stream has more strength which in turn strengthens the Azores High.

Kold, i agree about La Nina, its very hard to call, on the one hand, areas 1 and 2 were recording below average anomolies but on the other these were being balanced out by 3 and 4, now that 1 and 2 are stagnating, 3 and 4 are developing La Nina signals, its difficult to say, but i expect neatral ENSO conditions until November.

[beng]

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

Just to illustrate how poor June has been (although not technically cold in the CET zone) - have a look at the North Sea Temp anomalies now - the huge warmth has gone - indeed there's even signs of a negative anomaly developing off eastern Scotland - this must increase the chance that the CET value for July could be around average (or even below) if synoptics allow (something that I don't think was really possible in June due to that N Sea warmth and the predominance of Easterly winds).

Edited July 2, 2007 by beng