How the weather got ‘stuck’ over the UK—and produced an unusually dry and warm spring

Omega blocking highs can remain in place for several days or even weeks [image credit: UK Met Office]

” data-image-caption=”" data-medium-file=”https://tallbloke.wordpress.com/wp-content/uploads/2019/04/omega_block.jpg?w=300″ data-large-file=”https://tallbloke.wordpress.com/wp-content/uploads/2019/04/omega_block.jpg?w=614″ src=”https://tallbloke.wordpress.com/wp-content/uploads/2019/04/omega_block.jpg?w=300″ alt=”" width=”300″ height=”198″ class=”alignright size-medium wp-image-42357″ srcset=”https://tallbloke.wordpress.com/wp-content/uploads/2019/04/omega_block.jpg?w=300 300w, https://tallbloke.wordpress.com/wp-content/uploads/2019/04/omega_block.jpg?w=600 600w, https://tallbloke.wordpress.com/wp-content/uploads/2019/04/omega_block.jpg?w=150 150w” sizes=”(max-width: 300px) 100vw, 300px” />
As usual The Conversation uses any opportunity to promote its climate change dogma, even while admitting it has no specific evidence. Weather blocks are a well-known phenomenon and always have been. They resort to vague claims, for example saying computer models ‘suggest future changes in the occurrence of blocking’, which doesn’t impress much. Also ‘weaker jet stream’ theory has taken a knock as recent observational evidence points to the opposite.
– – –
A “blocking” weather system lingering high above the UK has produced one of the driest, warmest and brightest starts to spring on record.

April 2025 was the sunniest since records began in 1910. This followed the third-sunniest March, and both months saw temperatures well above average nationwide. On May 1, the temperature reached 29.3°C in Kew Gardens in London—a new record for the date.

Meteorologists are warning of the potential for a summer drought, as the UK has seen roughly half its usual amount of rainfall for March and April.

While farmers fret about this year’s harvest, some water companies are urging customers to help reservoir levels recover by limiting water use.
. . .
For several weeks, a stubborn area of high pressure over the UK has diverted the usual flow of mild, moist air from the North Atlantic like a boulder in a river. This is known as a blocking weather system.

Within it, air descends, warms and dries, which is why this weather pattern tends to be linked to heat waves and drought. Blocking is usually persistent, making it seem like the weather is stuck.

Here’s how climate change may have played a role in setting up this unusual spring. [Snip]
. . .
Keeping track of the jet stream
The movement of weather systems in Earth’s mid-latitudes—including over the UK—is linked to the jet stream, which is a fast-flowing river of air driven by the contrast in temperature between the poles and mid-latitudes.

Some researchers have suggested that, because the Arctic is warming faster than the tropics, the jet stream may weaken and become more “wavy”, increasing the occurrence of blocking events, contrary to what most climate models show.

Outside of the scientific community, this idea has become popular. However, the hypothesis remains controversial among scientists, and observational evidence has weakened in recent years.

In fact, around 10 kilometers above Earth’s surface, near commercial aircraft cruising altitudes, the opposite trends are occurring: the temperature difference between the Arctic and mid-latitudes is increasing, acting to increase the strength of the jet stream.

There are considerable challenges with understanding how climate change is affecting the large-scale atmospheric patterns which drive the weather we experience. These include large natural variability and imperfect climate models.

Models mostly suggest a decline in blocking events with climate change, though this remains relatively uncertain compared with other aspects of the science.

Full article here.
– – –
Image: Omega blocking highs can remain in place for several days or even weeks [credit: UK Met Office]