Spring / Summer 2010

[Milhouse]

I'm in neither camp at the moment. I'm not really expecting a really bad summer like 2007, nor am i expecting a really good one like 2006. Maybe its just i dont want to commit myself to going either way at such an early stage. However if i was to choose either way i would say a good summer was more likely than a bad one going on what the models are showing at the moment. The Azores High looks to be showing much more of an interest this year, compared of the past three where it was stuck well out to the west only making occassional visits.

[Gavin P]

Yes and similarily we could just be on the verge of a stinker of a summer, that more likely IMO, wasn't you going for a sub 10C even sub 9C year the other week well sounds like you've changed your mind surely a 1995 summer would mess that up unless you are counting on a cold autumn which is unlikely too.

I'm not really making a forecast, I'm just laying out what I found when I looked at summers with a developing La Nina and I found the closest match to the situation right now in the Pacific and Atlantic is 1995. Thats not to say 2010 will turn out like 1995, just that there does seem to be a similarity.

[johnholmes]

even if any domino effects make it this far around the world, surely there are far more significant factors closer to home which dictate our weather patterns.

I think many folk, professional and amateur, would tend to disagree with that comment.

We are beginning to realise that the whole set of teleconnections impinges fairly directly on our area. Such as El Nino or La Nina and even further out than that. Quite why its taken us so long is a bit of a mystery as the whole global set up is constantly linked. Time scales are obviously beyond a few days, often beyond 2 weeks or more but affect us they do.

[BlueHedgehog074]

Just a rough forecast at the moment, but I feel we could be looking at a fairly settled June, by the looks of the charts and maps with high pressure close by and making attemps to build itself over the U.K at times. ECMWF, in particular, shows some potential thundery weather breaking out much later next week as the strong(ish) area of high pressure rests itself over the East, with lower pressure situated in the Continent. As a result, we could see some very warm, humid air being drawn up from the South to help with the possible storm development and perhaps see some storms reach up from France.

Much as we could see some good dry periods, spells of wet weather could be possible at times (with the possibility of the thundery weather next week) and I think we could see a battle between the high and low pressure. In fact, I would probably say that the build up of the of low pressure to the East/South-East, which GFS show for the second week of June could win its way for a while considering how sturdy it looks. So perhaps wet and cloudy for week 2, and sunshine could be limited, especially in the East due to the North-Easterly winds.

However, I believe that the ridging of the high pressure we have seen in the last week, which also looking increasingly likely for next week may set the trend for the first pasrt of Summer and become more of an influence in the next few weeks.

[AderynCoch]

I think many folk, professional and amateur, would tend to disagree with that comment.

We are beginning to realise that the whole set of teleconnections impinges fairly directly on our area. Such as El Nino or La Nina and even further out than that. Quite why its taken us so long is a bit of a mystery as the whole global set up is constantly linked. Time scales are obviously beyond a few days, often beyond 2 weeks or more but affect us they do.

I would definitely agree that they affect us in one way or another, I'm just sceptical as to how much they affect us. I remember La Niña being roundly blamed back in 2007 for the wet summer we were having, yet La Niña was in action in 1995 when we had our driest summer ever.

I don't claim to be an expert in this area, I'm just curious.

[reef]

While patterns in the Pacific do of course have an effect on the weather here, its not always as cut and dry as that. Last winter was a prime example, with a moderate/strong El Nino going on past years we 'should' have been on for a rather mild, wet and windy winter (like 2006/07 in many regards), however in the end we got the coldest for 31 years. Likewise, Summer 2008 was a developing La Nina (similar to now it seems) but so was Summer 1995 I believe (though I could be mistaken), which was a very good summer.

I wouldnt like to make a forecast based solely on any teleconnection. Theres so many that producing a LRF is very much nothing more than educated guesswork (people who make them would tell you as much and it seems the MetOffice have given up completely). All you can do is look at the way things are trending and try make a prediction from there.

[johnholmes]

I think what helps get a better understanding of how much Ad is to look at all parts of the jigsaw/teleconnections. Nothing in meteorology can be isolated from another part, all must be taken together. What I was trying to say is that its only in the last few years that serious attempts have been made to link all these 'bits' together.

Thus, and remember this is a very basic idea here,

we start with the sun, then the interaction between the Strato- and Trops-spheres, each reacting with the other, Rossby long waves, the action of the sun on the Stratosphere, the creation of winds and there changes in direction-think of the warming events mentioned in technical comments during the winter half of the year especially

ENSO-El-Nino, La-Nina, QBO etc etc down into the hemisphere 500mb anomaly charts into the synoptic charts for 1-16 days ahead. They all depend on one another and are interlinked, some more closely than some others.

just a very, perhaps over simplified idea, but I hope that gives the overall idea.

Read the inputs from ch, GP, amongst just some for help in understanding the items mentioned above.

I've found it fascinating, and there is certainly scope for this branch of meteorology to develop into useful guidance for several weeks if not several months ahead.

However, like all forecasts don't expect perfection, but its certainly a better way of trying to predict weeks/months in advance than comparing this spring with last and suggesting what the summer might do for example.

That last comment is NOT a dig at anyone but an honest attempt to quantify which system will give the better results in my view.

just blowing my own trumpet a touch!

Over almost a 3 year period I found that, in my lrf posts, that trying to predict 15-30 days ahead gave, overall, about a 75% accuracy at 15 days and 60-65% at 25+ days.

Edited May 28, 2010 by johnholmes

[Weather-history]

Quite a number of recent Julys in years ending in "0" have been poor compared to the June

1910, 1920, 1930, 1940, 1950, 1960, 1970, 2000

1980 was a poor July.

1990 was an exception.

[summer blizzard]

I would definitely agree that they affect us in one way or another, I'm just sceptical as to how much they affect us. I remember La Niña being roundly blamed back in 2007 for the wet summer we were having, yet La Niña was in action in 1995 when we had our driest summer ever.

I don't claim to be an expert in this area, I'm just curious.

Unfortunately, we are not yet advanced enougth to be able to forecast with a high degree of accruracy a season ahead.

In regards to teleconnection patterns, i tend to look at the MEI (El Nino/La Nina) and also the QBO data in order to judge its effect upon the AO and in turn the NAO and PNA.

In regards to 2007 and 1995, the summer of 1995 was actually MEI neutral, not La Nina, this did not develop until early Autumn, whereas the summer of 2007 was indeed La Nina, now i am not saying all La Nina summers are bad of El Nino summers good, but it is an important factor given a positive corelation between the AO MEI in summer, though a neagative one in winter. Basically a La Nina in summer will encourage a negative AO, but conversly a positive one during winter, with 1995 an MEI neutral summer, other factors will have had a much bigger impact than 2007.

http://www.esrl.noaa.gov/psd/people/klaus.wolter/MEI/table.html

The next factor influencing the summers of 1995 and 2007 in my opinion is the QBO (a measure of weather the winds in the tropics are blowing westerly or easterly), and to be honest the QBO data could not be more opposite, 2007 had a mature negative QBO, and 1995 had a mature positive QBO, with a positive correlation to the AO all year round, this meant that without any other tropical forcing dampening the signal for a mid lattitude high, 1995 in hindsight was always going to be the better summer of the two, because 2007 effectively had the worst combination possible.

ftp://ftp.cpc.ncep.noaa.gov/wd52dg/data/indices/qbo.u30.index

In regards to summer 2010, at the moment we see a neutral MEI signal, and a mature negative QBO signal, which means that in my opinion, we will see a strong Azores High present over the Azores, with an Atlantic Low, this combination should mean that we will see a very traditional summer, high pressure to the south, lower to the north, with the dominant wind direction being south westerly (+NAO).

[Eugene]

Sounds nearer to 1985 than 1995.

http://www.weatheronline.co.uk/cgi-app/reports?LANG=en&MENU=seasonaloutlook&DAY=20100529

[johnholmes]

Sounds nearer to 1985 than 1995.

http://www.weatheron...ok&DAY=20100529

grief Eugene

one day PERHAPS we MIGHT get a glass half full type of post from you!

If you can find the negative then you sure seem to enjoy posting it-you must be a ray of sunshine at home.

[Gavin P]

WeatherOnline have had a very good couple of years with their seasonal forecasts, so this outlook is certainly concerning. As ever though, its only a forecast so no point taking it too seriously.

Edited May 29, 2010 by Gavin P

[Eugene]

Yes gavin i would take more notice of their forecasts than PWS for example but as ever nobody knows what the summer will bring we can all just have an opinion, it's been a great spring so far with an abundance of sunshine and hardly any rain until today.

Edited May 29, 2010 by Eugene

[kold weather]

I think the big difference between the 1995 and 2007 La Nina's is the strength of the event, 1995 had a slow evolving weak event that didn't get beyond -0.7C. Meanwhile the La Nina of 2007 got stronger then that and the Atmoshpere was very set into a La Nina setting. Seems to me that El Nino winters going into decent strength La Nina's tend not to be decent combinations for the summer...

That being said there can always be years that break the mould...

[William of Walworth]

In regards to summer 2010, at the moment we see a neutral MEI signal, and a mature negative QBO signal, which means that in my opinion, we will see a strong Azores High present over the Azores, with an Atlantic Low, this combination should mean that we will see a very traditional summer, high pressure to the south, lower to the north, with the dominant wind direction being south westerly (+NAO).

I'm concentrating on this post, because being a hopecaster type , I see plenty of scope for optimism should summer blizzard have it even half way correct....

To me, if the above turns out even half way valid, we'll see a more Northerly tracking Jet than's been dominating the last few summers.

[summer blizzard]

Kold, in regards to summer, 1995 did'nt even see negative MEI values (no La Nina at all), the same is true of this summer, we may be heading that way but we won't see a La Nina until at least Autumn.

[kold weather]

Well it all depends on what you class as a La Nina, offically it was a weak La Nina with -0.7C so I'll go with that, but either way it was very weak and probably the effects it had was probably pretty limited to the tropics anyway.

As for this summer, we already have daily temps down to about -0.7C and the weeklies are now down to about -0.2C with some big subsurface cold developing now and spreading up towards the surface. I can easily see us reaching La Nina in the weeklies by the end of June/Early July and probably reach it in the tri-monthlies some time in August.

[Thundery wintry showers]

Summer Blizzard's description sounds like it would be likely to give fairly close to average sea-level pressure but with a southerly bias brought about by the Atlantic low and prevailing south-westerlies (the prevailing wind direction in the summer quarter is traditionally more of a straight westerly).

This could point to a higher incidence of tropical maritime SW'lys and splits between a cool cloudy wet NW and warm sunny dry SE than usual- or alternatively, a warmer, more thundery summer than usual with an anomalously high frequency of southerly winds.

[Glacier Point]

First salvos of the summer fired.....

Originally model concensus was for a strong Azores ridge to build in towards the UK. Now, GFS ensemble mean height anomaly now shows the ridge magnetised to the western Atlantic and downstream trough located over north-west Europe. You can learn a lot from how models originally read marginal situations and then subsequently adjust.

http://raleighwx.easternuswx.com/models/gfsensemble/00zENS6-10day500mbHeightAnomalyNH.gif

No coincidence that global angular momentum is about to fall, a general trend for the summer given the emerging cold anomalies over the equator. Cold anomalies across the North Pacific and sub-tropical Atlantic (high pressure displaced northward) will asist the global circulation in working with falling angular momentum. This pattern is about right, and will persist all summer long IMO. Ridge to our west, trough to our east with us stuck in the middle.

Falling angular momentum will ironically lead to a mid latitude ridge developing more towards the UK during the period 5th - 10th June. But thereafter, this pattern will be very discernible. A cool and showery summer beckons.

[Thundery wintry showers]

Looking closely at the 6-10 day chart it does show a large ridge over the western Atlantic but the low pressure is sat to the west of Britain, with high pressure over Europe and a broad southerly flow over Britain.

I'm guessing that the idea is that the LP will migrate eastwards afterwards associated with the drop in angular momentum?

(Partly curious as acquiring a fuller understanding of these teleconnections will help with LRF-ing).

[SP1986]

Surely the point is that if this have changed they're not set in stone, so a cool showery isn't necessarily the final outcome?

[Glacier Point]

More a case of the upper low migrating south and south east as pressue builds over Iceland associated with angular momentum forcing the global wind oscillation towards phase 8. Composite for phase 8:

Further falling angular momentum towards phase 1 suggests a ridge to build into the UK:

[summer blizzard]

Having looked at data from a variety of different sources, my veiw of this summer is starting to dim, in that i don't think data supports an above average June, and all the data i have seen points to July been the coolest month of the summer, August will either be even worse, or better than both June and July.

Will release a detailed forecast on June 10th once May data is avialable.

[Gavin P]

First salvos of the summer fired.....

Originally model concensus was for a strong Azores ridge to build in towards the UK. Now, GFS ensemble mean height anomaly now shows the ridge magnetised to the western Atlantic and downstream trough located over north-west Europe. You can learn a lot from how models originally read marginal situations and then subsequently adjust.

http://raleighwx.easternuswx.com/models/gfsensemble/00zENS6-10day500mbHeightAnomalyNH.gif

No coincidence that global angular momentum is about to fall, a general trend for the summer given the emerging cold anomalies over the equator. Cold anomalies across the North Pacific and sub-tropical Atlantic (high pressure displaced northward) will asist the global circulation in working with falling angular momentum. This pattern is about right, and will persist all summer long IMO. Ridge to our west, trough to our east with us stuck in the middle.

Falling angular momentum will ironically lead to a mid latitude ridge developing more towards the UK during the period 5th - 10th June. But thereafter, this pattern will be very discernible. A cool and showery summer beckons.

We're going to see a very cool yearly CET for 2010 if your right GP! Coldest year since 1986 or 1987?

Edited May 31, 2010 by Gavin P

[Don]

We're going to see a very cool yearly CET for 2010 if your right GP! Coldest year since 1986 or 1987?

Yes we will indeed! The coolest CET since at least 1996 and probably the mid 80's. TWO's summer forecast has been released and looks rather mixed with the 2nd half in particular looking cool and unsettled. However, as always, we will see..... Remember, this time six months ago many of us thought that we were in for a mild Winter and we all know what happened next!