11 Jun 2013

What weather does the rest of summer hold?

Last week, we had our longest and most widespread spell of fine weather so far this year. High pressure sat over us, bringing plenty of sunshine and warmth, with temperatures widely in the low to mid 20s Celsius.

However, as is often the case with the British weather, all good things must come to an end. The next week or so will see a return to unsettled weather, with low pressure the main driving force.

You won’t be surprised to hear that this change in weather fortunes is down to the position of the jet stream – the fast-moving ribbon of air, high up in the atmosphere that determines the weather we experience at the surface.

Last week, it sat to the north of the UK, steering areas of low pressure and their wind and rain towards Iceland, leaving us to bask in the sunshine.

This week, the jet stream is going to move further south, which means that once again we are in the firing line from areas of low pressure.

However, it isn’t moving as far south as it did at the end of May. It will tend to sit over the UK. This means that as there are slight ripples in its position, there will be brief sunnier and warmer days sandwiched in between the generally unsettled weather.

What about the rest of summer?

With summer being a time of year when lots of us have outdoor plans, I’ve had no end of people asking me what the rest of the summer will be like.

In terms of day to day detail, it is just impossible to tell. However, there are general trends that can be picked out based on some of the longer range weather model predictions available from the UK Met Office and NOAA in the US.

Having looked at both of these models, there is a clear trend for the Azores high pressure to have more of an influence on our weather compared to last year.

Pressure and rainfall

There are signs of higher than normal pressure across southern parts of the UK and much of central and southern Europe, with occasional interruptions from areas of lower pressure.

This suggests to me that the general trend in the coming months is for a typically British summer. So, while there will be some settled spells with sunshine and warmth, there’ll also be some wetter weather – especially for northern parts of the UK.

As a result of this, I think that an extremely wet summer like last year is unlikely and rainfall will probably be fairly close to average.

Temperature

Having looked at the available information, it seems that temperatures this summer are more likely to be below average than above. There are two possible reasons for this.

The first reason is that the general trend for pressure patterns suggests that winds will come mainly from a westerly quarter, which is not the best direction for intense summer heat. Nevertheless, if the sun is shining, it’ll still feel warm even if temperatures are not that high.

Secondly, following the coldest spring in more than 50 years, sea temperatures around much of the UK are one to two degrees below normal. This has a moderating effect of cooling any hot air that moves towards us from below.

Finally, it is worth making the point that this is how things are looking based on the latest available information and things can, of course, change. As always, I’ll keep you updated here on my blog and also on Twitter – @liamdutton

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One reader comment

  1. Kasim Awan says:

    Hi Liam! Great weather blog as always. Funnily enough did a similar blog: http://kasimsweatherwatcher.com/solar-activity-mjo-the-latest/ .

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