Weather wise

The storms and floods at the end of last week, which turned the M1 into Britain's largest swimming pool, were the result of highly unusual weather conditions. An area of low pressure had been hovering around Britain for most of the week, while an area of high pressure, originally centred on Iceland, had gradually filled and spread southwards until it was lapping like a great tongue down into the Atlantic stretching as far as North Africa.

This high pressure area brought cold winds blowing from the arctic.

When such cold, dry air meets the warmer moister air of a low pressure area, it tends to seep underneath it (because it is heavier) forcing it upwards and cooling it to its condensation point. Result: rain. But at the same time, the heavy air ought to push the moist air out of the way - which is why rain tends to move across the country. In this case, however, the low pressure area that was feeding the storms refused to budge. It was fuelled by warm fronts from both the south and south-east, and had another aread of high pressure around Scandinavia hemming it in. Not only was there nowhere for it to go, but it did not run out of moisture to pour down on us.

Can we blame El Nino for all this? It seems reasonable to believe that if one part of the world is having weird weather, then it could affect the whole dynamical system of weather around the globe. But if that is true, we still do not understand the mechanisms behind it.