Why an omega block is causing record-breaking UK heatwave and deadly floods in Greece and Turkey

ITV News Weather Presenter Alex Beresford explains how an omega block works

The UK recorded the hottest day of the year - so far - on Thursday as a record-breaking early autumn heatwave baked the country.

Meanwhile, in holiday hotspots across parts of Europe, days of torrential rain has caused deadly floods.

The two extreme weather patterns are being driven by a phenomenon called an omega block. But what exactly is this?

What is an omega block?

The UK's heatwave is being created by tropical storms pushing a high pressure system over Britain, with the jet stream having moved to the north and bending into what is known as an omega blocking pattern.

Named after the Greek letter omega because of its shape, this system occurs when an area of high pressure gets stuck between two areas of low-pressure to the west and east and also slightly south.

The system has brought torrential rain and flooding for Spain and Greece, but hot, dry and clear conditions for the UK and central Europe.

Met Office chief meteorologist Neil Armstrong said: "An active tropical cyclone season in the North Atlantic has helped to amplify the pattern across the North Atlantic, pushing the jet stream well to the north of the UK, allowing some very warm air to be drawn north.

"It's a marked contrast to much of the meteorological summer, when the UK was on the northern side of the jet stream with cooler air and more unsettled weather."

What is the temperature threshold for a heatwave in the UK?

The Met Office defines a heatwave as three consecutive days of a particular region exceeding a given threshold, which varies around the UK.

For Scotland, Wales, Northern Ireland, Cornwall and northern England, the threshold is 25C; for Somerset, Hampshire and the Welsh Borders, 26C; the south coast, East Anglia and the East Midlands, 27C; and for London and the home counties the threshold is 28C.

Two extremes

Thursday provisionally became the hottest day of 2023 so far for the UK as temperatures hit 32.6C in parts of England.

However, that record be broken as early as Saturday, with the high temperatures expected to continue and peak as high as 33C.

Flooding brought about by the omega block, meanwhile, across Greece, Turkey and Bulgaria has left 18 people dead, as of Thursday evening, as severe rainstorms batter parts of eastern Europe.

Heavy rains in the region have submerged towns and villages and turned roads into rivers.

And in Spain, torrential downpours earlier in September led to the mayor of Madrid issuing a stay at home order.

The conditions, which were described as an "exceptional and truly rare situation in terms of precipitation", also led to the suspension of some rail services and a top tier men's football match.

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