As the school holidays get going across all of the UK now , I thought it would be worth asking our Chief Meteorologist, Ewen McCallum the question “Why is it more challenging to predict the weather in summer?”
This is what Ewen had to say:
Ah! those warm, lazy, hazy days of summer just lying on a beach or even in the back garden with the thoughts of those angry, wet and windy days of winter just a memory. Our own human behaviour in the summer season is one of the key challenges for the forecaster. We are out and about, having barbecues, putting up the tent or just messing about in a boat. Whatever we do we like to be in the big outdoors, whereas in winter who cares about run of the mill weather because inevitably it is the warm, central heated indoors that is the place to be.
So for most of the public the detail of the weather in summer matters; there is quite a difference between a cool showery day and a sunny warm day at the beach. However for the forecaster it is this emphasis on detail that proves a challenge.
Sure we are good at forecasting severe winter storms, which is a vital part of what we do. We are also excellent at predicting a change of type from cold and snowy to mild and damp. In other words we have become good at forecasting the overall picture a week ahead and in winter that’s all that matters to most people. However, in summer it’s the detail, ‘stupid’. Will the showers be inland or at the coast, when will the grey mist and fog clear to let the hot sun through; most people do not care in winter but in summer the differences can make or break your picnic.
Yes a four day forecast is overall as good as a one day forecast was 30 years ago but its forecasting for a post code where we need to do further research to become more accurate. In summer when the weather maps are relatively quiet it’s the local effects of the hills and valleys, land and sea and subtle variations in heat and moisture that dominate the weather outcome. The accuracy of a forecast is also dominated by perception and if your summer event is rained off despite being told that it is sunny just down the road, then you are not a happy bunny.