Charles Powell: A meandering jet stream that's leaving us all soaking wet

 

There are many factors which can impact the notoriously changeable weather in the UK, so no single one on its own can be said to be fully responsible. However, it is possible to isolate contributing factors and, in this case, one of those is the northern hemisphere jet stream.

This is a narrow band of fast flowing westerly winds (i.e. blowing from west to east) in the high atmosphere. This band moves around and also changes its track, from a fairly straight line to something resembling a meandering river.

In April we have seen what we term a "blocking pattern" in the jet stream, where it meanders north and south instead of making its more usual eastward progress.

The UK found itself under a southerly meander, with the jet stream passing over France and Spain. This atmospheric set up brought slow-moving, low-surface pressure, cloud and rain.

As we head into May it looks as though the unsettled theme to the weather will continue, with further showers or more prolonged rain, but there will be a few drier and brighter days in between.

By its very nature, the weather becomes harder to predict the longer the outlook period is. The science behind long-range forecasting is still in its infancy and no one can predict with any confidence exactly what is going to happen months in advance.

The writer is a forecaster with the Met Office

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