Unusual rainfall pattern could lead to a colder-than-usual start to winter

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forecasters have predicted an increased chance of a colder-than-usual start to this winter due to a change in Arctic conditions and “unusual” tropical rainfall patterns.

The Met Office said the conditions mean there is a 30 per cent likelihood the mercury will plunge at the beginning of this winter –the highest risk of a cold start since the bitterly cold season of 2010/11.

But the agency said it was too early to predict whether it would be a snowy, wet or dry three-month period from November.

The key factors leading to colder temperatures include “disturbed” stratospheric Arctic winds known as the polar vortex, which affects the jet stream, and a La Nina, the opposite of an El Nino, bringing lower temperatures in the tropics.

But the Met Office pointed out there was still a 70 per cent chance of milder temperatures and, following a reversal in expected atmospheric patterns in February, the prevailing westward winds could increase the chances of warm and wet conditions.

Forecasters reached the long-range prediction after feeding their analysis of those factors into a computer model, with the result higher than the expected 20 per cent probability suggested by a 30-year rolling average up to 2010.

Professor Adam Scaife, head of long-range prediction at the Met Office Hadley Centre, said: “The risk of a cold start to winter
has increased to 30 per cent this year.

Statistically, however, it is still more likely that the UK will experience a normal start to winter, but there is an increased risk of cold snaps between now and Christmas, although this doesn’t necessarily mean we will get large amounts of snow.

“Several factors, including tropical rainfall, are known to drive UK and European winter conditions: following a strong
El Nino last year, the tropics are now influenced by a weak La Nina.”

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