Fine weather to return

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  • A satellite image illustrating the developing low pressure system which crossed the British Isles on Saturday 3rd September 2016.

    A radar image showing the heavy rain which fell widely across central and southern Britain on Saturday 3rd September 2016.

    A NCEP forecast map showing warm air advection across the Britiish Isles and western Europe.

    A schematic illustrating the process of warm and cold air advection near the UK.

  • Fine weather to return
    03.09.2016 13:13

    A developing low pressure system sweeped eastward across central Britain Saturday bringing heavy rain and strong winds to many areas.  The low pressure system will exit into the North Sea early on Sunday to leave a bright day with sunny spells and some showers. On Monday another weather system is expected to move eastwards bringing rain to some areas.

     

    However, the unsettled weather is not here to stay. Global weather models are now indicating the development of a large high pressure cell near the British Isles. This high pressure system is expected to sit close to southern and eastern Britain throughout the coming week shielding much of the country from areas of low pressure in the Atlantic.

    Back to school sunshine

    On Tuesday, high pressure will begin to build across southern Britain with low cloud breaking to allow warm sunshine to develop. Cloud and patchy rain may plague western Ireland and Scotland though. By Wednesday a southerly air-flow will have pushed any lingering rain bands into the Atlantic to leave much of the British Isles warm and sunny. Temperatures in south-eastern England will reach the mid-twenties and it will feel very humid.

    The fine conditions are expected to persist on Thursday and Friday with very warm air being advected north from the continent. Temperatures by Friday could reach the high twenties in the south-east.

    What is advection?

    The official meteorological definition is "Horizontal transport of an atmospheric property, such as temperature and moisture". In the case of temperature, strong temperature advection occurs when there is a rapid rate of change of temperature due to the onset of warmer/colder wind flows.

    It is worth considering that the temperature can vary as a result of the time of day and season but also by the movement of air from different source regions - we call them airmasses. The UK lies at a crossroads of contrasting airmasses, and frequently experiences advection of air from different parts of the globe; e.g. the Atlantic, Spain and North Africa or even the Arctic. This is why our weather is so changeable.

    Next weekend

    Current indications suggest a spell of more unsettled weather will edge in from the Atlantic next weekend but this is subject to a high degree of uncertainty.

    Make sure to check back for regular updates on the developing fine spell next week!

    By: Matthew Martin