Sea Surface Temperature And Sea Ice Trends

[AtlanticFlamethrower]

Might the winter la nina cold anomaly have migrated northwards somehow, up the west cost of N America?

[summer blizzard]

Glacier Point, i am troubled by the current sea surface temperature anomolies in the Pacific Ocean as the positive anomoly in the central Pacif appears to be joining to the warm anomoly above it, if this happened, this would favour a ridge over the western USA rather than a trough, can you shed any light on the situation.

I have illustrated a chart to show the possible Jet Stream tracks.

[JoeShmoe]

Am I right in thinking the UKMO will base their winter 06/07 forecast on the SSTA profile from late May? If so any guess what they'll go for with all those cold anomolies about and severe ice melt?

[summer blizzard]

I believe that they will go for an NAO value of -1.3 because the sea surface temperature anomolies are very similar to last year.

Interestingly, a cold sea surface temperature anomoly between Greenland and Iceland has formed, if this can link with a cold sea surface temperature anomoly between Newfoundland and Greenland, then mid-lattitude blocking will be almost guaranteed.

[summer blizzard]

It is interesting that the warm anomolies along the west coast of the USA and southern Alaska are continuing to grow, this indicates the emergance of a more poisitive PNA pattern likely in late summer should the warm anomolies continue to grow, if the NAO is still negative when the pattern change to a sustained positive PNA sets in, then cool and unsettled weather seems very likely.

[Glacier Point]

http://www.met-office.gov.uk/research/seas.../nao/index.html

Looking at the algorithm and predictor pattern generated from last May's SSTA, I would suggest that a more negative NAO signal will be the most likely punt.

The main difference to May 2005 would appear to be the stronger negative anomalies across the sub-tropical Atlantic - a sign of the polar front descending earlier and longer south of the UK perhaps.

GP

[summer blizzard]

A slight warm anomoly has appeared to the west of Canada, should this anomoly keep on growing, then a cool and unsettled end to summer is on the cards with a positive PNA and negative NAO pattern, this seems to fit in well with Glacier Points summer forecast which suggested an increased possibility of a warm start to summer cancelled out by a poor end.

[summer blizzard]

I have anotated todays chart and a chart from a year ago to show the teleconection patterns then and now, as you can see the situation in the Pacific is a lot different this year as the PNA is more enclined to occilate between positive and negative this year than last year as opposed to being in a largely positive modeas it was last year, therefore the Jet Stream may be more xonal than last yearover the USA. In the Atlantic, the anomolies are fairly similar with the western Atlantic Occilation and the NAO inclined to be in a negative mode, with the main blocking likely to be in eastern Canada, the main difference this year is likely to be in the eastern Atlantic where a Euro trough is favoured over a a Euro ridge, therefore, a mid-Atlantic block is likely.

In summary, over the next month i expect the following teleconection values to be dominant.

PNA - neutral - blocking patterns over western Atlantic indicating developing positive PNA conditions

NAO - negative - likely to stay negative for foreseable future

WAO - negative - mean trough likely in association with developing positive PNA

EAO - neutral - low in GIN sea favouredm block over or just to west of British Isles favoured, no domiant pressure pattern to west of Spain favoured

CO - negative - trough over Scandinavia and Europe favored

While nearly all teleconections favour cooler and unsettled weather, there are conflicting signals in the eastern Atlantic, should the EAO become positive, conditions would mirror those of 1995.

[Dawlish]

I have anotated todays chart and a chart from a year ago to show the teleconection patterns then and now, as you can see the situation in the Pacific is a lot different this year as the PNA is more enclined to occilate between positive and negative this year than last year as opposed to being in a largely positive modeas it was last year, therefore the Jet Stream may be more xonal than last yearover the USA. In the Atlantic, the anomolies are fairly similar with the western Atlantic Occilation and the NAO inclined to be in a negative mode, with the main blocking likely to be in eastern Canada, the main difference this year is likely to be in the eastern Atlantic where a Euro trough is favoured over a a Euro ridge, therefore, a mid-Atlantic block is likely.

In summary, over the next month i expect the following teleconection values to be dominant.

PNA - neutral - blocking patterns over western Atlantic indicating developing positive PNA conditions

NAO - negative - likely to stay negative for foreseable future

WAO - negative - mean trough likely in association with developing positive PNA

EAO - neutral - low in GIN sea favouredm block over or just to west of British Isles favoured, no domiant pressure pattern to west of Spain favoured

CO - negative - trough over Scandinavia and Europe favored

While nearly all teleconections favour cooler and unsettled weather, there are conflicting signals in the eastern Atlantic, should the EAO become positive, conditions would mirror those of 1995.

Hi Summer,

I do enjoy reading your posts and I think the effort and obvious depth of knowledge you put into these forecasts of yours is excellent - though I feel that long-range forecasting has a long way to go yet, as you have probably picked up(!). However, in this one, with the NAO being positive for the last 2 weeks, I don't understand why you think it will be negative over the next month and likely to stay negative for the foreseeable future. Wouldn't the well established positive pattern be more likely to continue, than to change?

Paul

[Glacier Point]

Paul,

Summer Blizzard has picked up the very distinctive banding of cold SSTAs in the sub-tropical Atlantic and warm anomalies to the north of this - inverting the normal gradation (anomalies not empirical) of sea temperatures and the baroclinic responses they are likely to bring about.

Warm anomalies in the northern Atlantic over cold anomalies to the south and to a certain extent cold anomalies further north are one factor in helping to force the mean pressure in the Atlantic lower and rising pressure to the north over Greenland and Canada.

Whilst SSTA variance might explain 60% of long term pressure anomalies, other factors are at play, not least the reduced impact of SSTA during the Summer and sometimes conflicting teleconnections such as the AO. At present the +ve AO is forcing the NAO neutral - positive although this situation may change.

Funnily enough, a -ve NAO could, if the blocking were to be far enough west over Canda, be very good for our Summer in helping to promote the Azores-Iberian weakness that we have observed so far which keeps sustaining high pressure over or just to the east of the UK.

GP

Edited June 13, 2006 by Glacier Point

[Dawlish]

Paul,

Summer Blizzard has picked up the very distinctive banding of cold SSTAs in the sub-tropical Atlantic and warm anomalies to the north of this - inverting the normal gradation (anomalies not empirical) of sea temperatures and the baroclinic responses they are likely to bring about.

Warm anomalies in the northern Atlantic over cold anomalies to the south and to a certain extent cold anomalies further north are one factor in helping to force the mean pressure in the Atlantic lower and rising pressure to the north over Greenland and Canada.

Whilst SSTA variance might explain 60% of long term pressure anomalies, other factors are at play, not least the reduced impact of SSTA during the Summer and sometimes conflicting teleconnections such as the AO. At present the +ve AO is forcing the NAO neutral - positive although this situation may change.

Funnily enough, a -ve NAO could, if the blocking were to be far enough west over Canda, be very good for our Summer in helping to promote the Azores-Iberian weakness that we have observed so far which keeps sustaining high pressure over or just to the east of the UK.

GP

Thanks Glacier, I see the idea, but whilst Atlantic pressure, certainly North of our latitudes will be low, the pressure over Greenland, both on the gfs and the fax charts, is forecast to stay low for the next 5.5 days, at least and possibly for the next 2 weeks according to the 12z gfs.

I know the Met Office would like SSTs to explain a good 60% of the long-term pressure anomalies, but I'm not sure a success rate of only 67%, over the last 30 years, linking Early summer SSTs with winter pressure patterns, via the NAO and therefore with our ensuing winter weather, leads us to that high a confidence in the percentage. Not sure of that though - I have no figures.

Paul

Edited June 13, 2006 by Dawlish

[summer blizzard]

By looking at the latest chart, you can see that the cold anomolies in the central Pacific have firmly connected and that the cold anomoly to the west of Canada is being eaten away indicating the onset of positive PNA conditions, assuming that the cold anomoly to the west of Canada has dissapeared completely by the end of June and that the time lag between sea surface temperatures and synoptics is one month, which is between my and Glacier Points estimates, we can assume that a positive PNA will be in place for August, combined with a negative NAO, so i have decided to take a look at some anologues for August.

ftp://ftp.cpc.ncep.noaa.gov/wd52dg/data/i...s/tele_index.nh

I am looking for Augusts with a NAO value of -1 or less and a PNA value of 1 or more...

The anologues which i have found are:

1958

1960

1966

As you can see from the anomoly map below, there is strong blocking over Greenland with the Jet Stream over the British Isles.

The CET and rainfall statistics for those months are:

1958 - 15.8C - 0.4C below average

1960 - 15C - 1.2C below average

1966 - 14.7C - 1.5C below average

Interestingly, 14.7C is my forecasted value for August and a CET of less than 15.9C would make this the coolest August since 1993 and a CET of less than 14.6C, would make this the coolest August since 1922.

http://www.metoffice.com/research/hadleyce.../HadCET_act.txt

1958 - 102mm

1960 - 111mm

1966 - 112mm

Interestingly, there seems a strong corelation with rainfall.

http://www.metoffice.com/research/hadleyce.../HadEWP_act.txt

In my opinion, a cool and wet August is looking likely.

[BLAST FROM THE PAST]

Summer

Good posts and analysis, will monitor the situation only to view how effective the teles are in telling us what is likely to happen. I will agree with wet August but think very warm to the end with Indian summer potential again!

BFTP

[summer blizzard]

Interestingly, my teleconection forecast does point to a warm start to September although that will be offset by a cool middle and end resulting in a slightly below average CET.

Edited June 15, 2006 by summer blizzard

[summer blizzard]

The latest chart suggests a mid-Atlantic ridge with a trough over western Europe, as for the positive PNA development, while the cold anomoly in the central Pacific is still evident, the warm anomolies to the west of Canada have declined, suggesting a still dominant negative PNA.

[summer blizzard]

The latest sea surface temperature chart supports neutral to negative PNA with a ridge near Alaska and a trough over Canada and Greenland with a ridge over Scandinavia.

[summer blizzard]

An update on the SST situation...

The major cold pool in the Pacific is gradually moving eastward indicating a central Pacific trough, this means that while warm anomolies are not yet established in the eastern Pacific, the PNA is being forced slightly positive and will be during July, the warm anomolies to the north of the cold anomoly are also moving eastwards encouraging the development of a strongly positive PNA by August.

The anomolies in the Atlantic are indicative of a positive NAO, with a trough to the west of the British Isles and high pressure over Europe however as the positive PNA becomes stronger, a pattern change to a negative NAO may occur during August.

[johnholmes]

to an old bugger like me much of that is Greek, but I'm sure its right. I just wished I understood all this!

puzzled old senior forecaster!

John

[Damien]

The major cold pool in the Pacific is gradually moving eastward indicating a central Pacific trough, this means that while warm anomolies are not yet established in the eastern Pacific, the PNA is being forced slightly positive and will be during July, the warm anomolies to the north of the cold anomoly are also moving eastwards encouraging the development of a strongly positive PNA by August.

The anomolies in the Atlantic are indicative of a positive NAO, with a trough to the west of the British Isles and high pressure over Europe however as the positive PNA becomes stronger, a pattern change to a negative NAO may occur during August.

Yes, that's what NOAA is also suggesting. :lol:

I think/would not be surprised to see it flip back to positive for September though, giving us classically milder conditions. :lol:

Edited June 28, 2006 by Damien

[summer blizzard]

I would be suprised if that happened, as the anomoly seems to be moving east at around 20 degrees each month, which means that September and October should see the most positive PNA values although there is a chance of the PNA becoming negative in time for winter.

[summer blizzard]

The cold anomolies in the GIN sea are now moving into the North Sea which may mean a more unsettled period as we head towards August.

[BLAST FROM THE PAST]

I would be suprised if that happened, as the anomoly seems to be moving east at around 20 degrees each month, which means that September and October should see the most positive PNA values although there is a chance of the PNA becoming negative in time for winter.

SB

Clarify if you will +ve PNA means what for UK and vice versa

BFTP

[summer blizzard]

The PNA vale refers to the Jet pattern over North America, a positive PNA is indicative of a ridge over the west coast of the USA and a trough over the east of the USA pulling the Jet Stream south.

I believe that a positive PNA is a good thing regarding cooler weather because it encourages a southerly tracking Jet Stream coming out of the USA.

[BLAST FROM THE PAST]

The PNA vale refers to the Jet pattern over North America, a positive PNA is indicative of a ridge over the west coast of the USA and a trough over the east of the USA pulling the Jet Stream south.

I believe that a positive PNA is a good thing regarding cooler weather because it encourages a southerly tracking Jet Stream coming out of the USA.

Crystal clear, thanks SB

BFTP

[shuggee]

That's a big +ve anomaly off the east coast of North America - which is getting warmer and warmer.