29 May 2013

Are we about to get a taste of summer?

Over the past couple of days, I’ve mentioned that there are hints that a spell of more prolonged settled weather could be on the horizon.

Whilst the detail is not yet concrete, there continues to be signs that we might see a burst of summer-like weather next week.

Following a long, drawn-out winter and a spring that is on course to be the coldest in over 30 years, the arrival of a longer spell of fine, warm weather would most definitely be welcome.

So far this spring, any bursts of warm weather have tended to be short-lived, lasting just a few days before colder, wetter weather made a return.

Next week, high pressure could hang around for longer, meaning that there is the potential for nicer weather to stick around.

Why the change?

Once again, the position of the jet stream is responsible for the possible change in our weather fortunes.

For much of spring, the jet stream has been unusually far south, taking the typical mix of rain, sunshine and spring warmth further southwards across Iberia, the Mediterranean and the Balkans.

Even though it has moved a bit further north in the past few weeks, it hasn’t been enough to keep unseasonably wet and cold weather away.

However, this weekend, the jet stream is set to move to the north of us. This will steer areas of low pressure, along with their wind and rain, further northwards towards Iceland, rather than here.

As a result of this, high pressure from the Azores will build across the UK, bringing drier, brighter and warmer weather.

How confident is the forecast?

This is where the difficulty arises. There are three main weather models that forecasters look at when predicting the weather – the American GFS, the European ECMWF and the UK Met Office.

The good news is that they all agree on building high pressure over us into the early part of next week. The bad news is that they differ slightly on how strongly high pressure builds, which will determine for how long any fine and warm weather stays with us.

The best case scenario would be for high pressure to stay centred across the UK, as this would bring sinking air, suppressing cloud formation and thus allow more sunshine.

In addition, because the there are more hours of daylight than darkness at this time of year, the surplus of incoming solar radiation would allow the air over us to warm a little more day by day, giving increasing warmth.

How warm could it be?

The key to answering this question is dependent on where the area high pressure sits and for how long.

At the lower end of the spectrum, temperatures will reach a pleasant 17-21C. However, in the best case scenario, temperatures could reach a toasty 22-25C.

Towards the end of the week, the detail should hopefully become a bit clearer. I’ll of course keep you updated with the latest here on my blog and also on Twitter – @liamdutton

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