An omega block is answerable for the heatwave which is gripping elements of the UK.
Right here, we check out the climate sample – and whether or not local weather change might make it a extra frequent function within the years to return.
What’s an omega block – and the way does it get its identify?
Blocks can interrupt the traditional eastward development of our climate.
With an omega block, excessive stress – which usually brings hotter and extra settled situations – turns into sandwiched between two low stress methods.
It varieties a form just like the Greek letter Ω, therefore its identify.
How does the omega block influence the jet stream?
Climate methods often transfer from west to east at our latitude, however typically they’ll get blocked when the jet stream weakens and buckles.
The jetstream is a core of sturdy winds excessive above the Earth’s floor which helps to develop and steer areas of low stress across the globe.
When there’s a whole lot of tropical storm exercise within the North Atlantic, this will bend the jet stream, which is what has occurred on this event.
The place and energy of the jet has resulted in a blocking sample the place the excessive stress turns into caught between the 2 low stress methods.
How lengthy can such a block sample final?
Climate blocks can persist for days, weeks, and even months.
One well-known instance was in the summertime of 1976, when temperatures of above 30C introduced drought situations and persevered for lengthy intervals.
How is the block impacting the UK and Europe’s climate?
Excessive stress simply to the east of the UK and centred over Scandinavia is permitting a feed of sizzling and humid air from the south.
Nonetheless, low stress areas are affecting both facet of the Mediterranean, with the remnants of Hurricane Franklin to the west of Portugal and Storm Daniel bringing torrential downpours to Greece.
Temperatures of above 30C (86F) in September have solely occurred a “handful of instances” within the UK – and it will likely be the most popular day of the 12 months if it climbs above 32.2C (89.96F).
Forecasters say it’s probably temperatures will stay over 20C (68F) at evening in lots of areas.
Situations are set to alter with thundery downpours slowly transferring in from the west afterward Wednesday.
Is local weather change making these warmth domes extra frequent?
Sky climate producer Kirsty McCabe stated there’s growing proof the jetstream is being weakened by local weather change.
She stated: “Blocked climate patterns reminiscent of omega blocks or warmth domes appear to be taking place extra often in latest a long time, and that may very well be linked to the results of local weather change on the jet stream.
“There may be some analysis that implies the jetstream is weakening because of a discount within the temperature distinction between the equator to the pole because the Arctic has warmed at roughly twice the speed as all the globe – scientists seek advice from this as ‘Arctic amplification’.”
What are the dangers of such a warmth dome?
A cussed space of excessive stress means already heat or sizzling air trapped beneath the excessive will proceed to turn into hotter, making a warmth dome.
Kirsty added: “Sizzling air will rise into the ambiance, however excessive stress acts as a lid and causes the air to subside or sink. Because the air sinks, it warms by compression, and the warmth builds.
“The bottom additionally warms, shedding moisture and making it simpler to warmth much more.
“Till the stress sample adjustments, the excessive will proceed to exacerbate the recent situations, bringing a threat of wildfires, drought and heat-health points.”
Are there some other frequent block patterns?
The Met Workplace says there’s additionally a diffluent block together with omega.
Diffluent occurs when there’s a “cut up within the eastwards stream” – and might see excessive stress pushed to the north of a low centre within the south, bringing extended intervals of comparable climate.