The Weather Review

Weather Update

The proverb goes that April showers brings forth May flowers, but this year the showers fell mainly in May. So, what brought about the difference? As with all weather in the UK it is down to the jet stream, the tropospheric super-highway that wings its way across the Atlantic to deliver weather systems to Europe.

In April, the jet stream was weak and running to the south of the UK, meaning that the weather systems were not as transient as usual and that the dominant pattern lingered longer than normal. This is what brought the sunny, calm weather in April. May, however, saw a stronger jet stream that crossed the UK, bringing in low pressure systems from the Atlantic. Low pressure systems are synonymous with wetter, windier, cooler weather. There was so much rain that some regions of the UK saw over 200% of the average rainfall for May.

This behaviour of the jet stream was also the reason for the cooler than expect temperatures in May. Cooler air masses from the Artic and Greenland hitched rides on the Atlantic low-pressure systems, leading to the coldest May since 1996.

The weather conditions were borne out in our wind and solar generation, with wind output hitting seasonal average levels. The hours of sunshine metric for May were markedly below average (for reference the hours of sunshine in 2020 was 265hrs and 2021 was 160) which is unsurprising given the cloudy, grey outlook we experienced. 

But, very untypically for British weather, the sun came out in time for the late May Bank Holiday. Again, this was thanks to the jet stream moving north, which effectively blocked low pressure unsettled systems coming in from the west and drew high pressure sunshine and warmth from the south-east. The “warmest day of the year” had a new winner virtually every day from the last days of May into early June, and that summer feeling is expected to last until early to mid-June if current forecasts can be believed. Sun cream, sunglasses and ice cream at the ready.