Settled, Cool Theme For Much Of UK Through Wednesday, Dull, Damp In Southwest (Includes HD Video)

Written by on October 7, 2012 in United Kingdom & Ireland with 6 Comments

Courtesy of Mark Vogan

The cold high dominating the UK except for the far southwest is set to hold through Wednesday. With the jet just south of the UK and a high sitting over the UK, this acts as a block to a weather system trying to push a front into the Southwest. The fact this high is north of the jet stream, this means the sunshine will have limited warmth and will support rather chilly nights. There is some very cold air suspended aloft, which is a limiting factor to how much daytime warmth there is. The next 3 days looks glorious for the majority with lots of autumn sunshine accompanied by cold, frosty nights.

The fly in the oinment will be Devon, Cornwall extending into Dorset, Somerset up into South Wales where a front will linger bringing wet, cloudy, dreary but mild weather here along with a stiff breeze. The clouds associated may spread east across the heart of the South, perhaps reaching London at times but here, along with the rest of Britain and Ireland, it should be largely dry with plenty of sunshine.

Bright, mostly sunny days are followed by cold, frosty nights

Think it was cold last night?

It may be colder the next few nights or certainly very frosty at least. These chilly starts also make for slower recovery in temperature by day, so keep in mind that as the sun’s angle lowers and there’s less heat reaching the surface thanks to the low heights within the trough above, that means, colder nights may lead to cooler days which in turn makes it easier for the atmosphere to cool once the sun goes down… In other words the step down process of cooler nights results in cooler days through Wednesday. The coldest night may come Tuesday or Wednesday night IF conditions remain the same. Not only frost but patchy ice may start to show up, so take care whilst driving to work in the coming mornings.

Here’s the GFS surface pressure today through Wednesday. Looking fantastic!

Breakdown comes Thursday!

According to the models, the change should come by Thursday as the high breaks down and the patiently waiting fronts spread northeastwards with their rain, wind and milder southerly air flow.

The jet lifts north so this sould introduce milder air and none frosty nights.

Here’s the precipitation forecast off the GFS by Thursday and Friday.

High gets replaced by low Thursday/Friday but could the high return to South next weekend?

Check out these pressure charts for Thursday, Friday. Gone is the high from British airspace BUT notice it’s not far to the east or west….

If you notice, there’s a pretty good system winds up off Scotland with pressure down below 1000 mb. After winds blow southerly, with the low pushing east and according to the model north, then winds veer back towards a NW and then W direction. The movement of this low would also suggest warmer air and ridging trying to build into the southern hald of the UK by next Saturday. Here’s a look at the chart for next Saturday.

This setup may support mild, settled weather for the south while it stays more unsettled in the north. Opposite to this weekend and early part of the week ahead.

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  1. Jamie says:

    That makes crystal clear sense to me, despite being blonde. Thanks for clarifying.

    This morning I saw frost on the grassy verges of Dunfermline (those in shade) at approx 9.30 am.


  2. Jamie says:

    Hi Mark

    I can’t understand why these clouds only appear during the day and disappear by night? What is the process that causes this?

    Is it cause the ground is colder than the sky at night? hence all the condensation sticks on the grass rather than in the sky?

    I’m confused. Can you tell I’m blonde lol?


    • Mark Vogan says:

      It’s as the sun heats the surface after sunsrise at the lower atmosphere heats, this forces the air to rise, cool and condense to form clouds. The dymanics are lost once the sun goes down and so clouds dissipate..

  3. Jamie says:

    Hi Mark. Just a quick question: why do the clouds disappear on cold nights such as tonight?



    • Mark Vogan says:

      The clouds really only develop by morning once the sun comes up and the surface warms and they linger through the day but once the atmosphere cools, they disspiate.

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