Making Decisions for the Ever Changing Weather

The weather is often the first topic of conversation when we meet friends in the street or when shopping in town. Many of us have to endure the natural elements which can affect us all at some point in our lives. Rob Harrison looks at the UK climate to explain why it can be so varied – and how technology at the Met Office is helping the commercial world to use weather forecasts to manage risks, plan operations and ensure health and safety.

The climate across the UK is one that invariably presents a wide range of weather types. What makes the weather even more remarkable in this country are the changes we see over a relatively short period of time.

As the UK’s national weather service, the Met Office provides a wide range of weather and climate information to the public, government and businesses including the financial world, energy industry, airline companies

and rail networks. So why does the weather change so often in the UK? Textbook descriptions of our long term weather describe the climate as temperate. This is one where the summers are cool rather than very

warm or hot - winters milder rather than cold. The geographical position of the British Isles puts them very much at the ‘crossroads’ for different weather patterns. Just to the south and east, there is the land mass of continental Europe, while to the west the world’s second largest ocean provides a vast supply of moisture when winds blow in off the Atlantic. Add to the mix, the fact we are a small island nation - introduces

further local effects on our climate, with the seas and ocean helping to influence what weather we actually get. Across north western parts of Europe, the winds usually blow from a south westerly direction. As this moist air, in the form of cloud, rain or showers, reaches our shores from the west, it is these areas that receive the highest rainfall totals. Predominate south westerly winds that affect the UK is ultimately caused by the differential heating of the Earth’s surface by the Sun. This establishes a global circulation of the atmosphere, with warmer air from the tropics heading North Pole in the northern hemisphere. The direction of this flow is deflected to the right by the rotation of the Earth. Clearly, the persistence of south westerly winds does vary as the fluid nature of the atmosphere fluctuates through the seasons. What are referred to as ‘blocking’ weather patterns occur from time to time - steering Atlantic weather systems around the UK.