Friday 24th July
After a very sunny start to Thursday variable cloud began to drift across, however the heat began to build in the afternoon exceeding the heatwave threshold for Wiltshire of 27C, with a maximum of 27.4C at 16.34, being 4.5C above my long-term July average. The breeze was exceptionally light with a maximum movement, couldn’t be called a gust, of just 9mph at 19.59. The past night gave us the warmest night since the 15th with a minimum of 14.2C in the very early hours at 02.05 being 2.2C above average. The back track of the radar showed a considerable bank of cloud arriving around 00.30 which explains why the thermometer did to continue to drop until around sunrise, as on previous mornings. Due to the variable cloud the UV level of 5.1 was at the bottom of the High category, and of course we are over a month since the longest day.
Friday began cool thanks to the thick bank of cloud to the east that limited any strong sunshine until just after 08.00, by which time the thermometer had risen to 16.6C.
The centre of the anticyclone has eased away a little further. The barometric pressure has fallen 4mb since yesterday and currently is falling very slowly, that is allowing the low pressure around Iceland to edge closer. This will result in more cloud arriving from the north and a likely weak, cold front crossing early Sunday. At the moment there is a conflict of opinion as to whether this front will have petered out as it reaches southern England and be devoid of any precipitation. As a gardener, I really hope the BBC forecast is correct with the possibilty of light rain, but whatever, it will be minimal in quantity.
There will be some relief in the high temperatures from Saturday although the respite will be short lived as the Jet Stream forecast is for it to return to flow a little further north of the UK, which will result in very high temperatures returning on Tuesday that will likely be above the heatwave threshold again for the rest of that week.
From today the breeze will have a more northwesterly component, rather than the persistent northeasterly recently, hence the small drop in temperatures, that by Sunday is likely back further and come from the west.
yesterday I added part of a recent article on the main heatwaves, part 2 today.
Impacts on marine ecosystems
Warmer seas can have important consequences for marine life. Species that are typically found further south can expand their range northwards when waters remain unusually warm for prolonged periods.
One example highlighted by Met Office researchers is the octopus. Traditionally more common in warmer waters further south, octopus populations have increasingly been observed around southwest UK waters.
Changes such as these demonstrate how marine heatwaves can reshape ecosystems and alter the distribution of species around UK coastlines.
How warmer seas affect our weather
Marine heatwaves can also influence weather conditions over land.
Sea breezes often provide cooling during hot summer weather, particularly close to the coast. However, when sea temperatures are unusually high, this cooling effect becomes weaker.
Forecast modelling has shown that marine heatwave conditions can lead to air temperatures more than 1.5°C warmer over surrounding seas, with the warmer air subsequently transported inland by sea breezes. This means coastal areas may receive less relief from hot conditions than would normally be expected.
Why UK seas are particularly vulnerable
The waters surrounding the UK are relatively shallow compared with many parts of the world’s oceans. Much of the North Sea, for example, is shallower than the height of the Eiffel Tower.
Combined with strong tidal currents, this creates a unique environment where heat can become trapped and mixed throughout the entire water column. Rather than remaining solely at the surface, warmth can be distributed through much of the sea depth, allowing heat to persist for longer periods.