An unusual weather effect is likely to bring exceptionally high temperatures back to the UK this week.
The Foehn effect could see temperatures rise again in parts of northern Scotland on Wednesday.
Following the hottest weekend of the year so fartemperatures dropped to medium to high levels.
But forecasters warned that parts of northern Scotland could see temperatures rise to 24C or even 25C – well above the seasonal average.
This may be due to the Foehn effect, which occurs when the air on the downwind (or leeward) side of a mountain is warmer and drier than the air on the other side.
When air is forced up over a mountain, it cools and condenses to form clouds, bringing rain to the side upwind of the mountain.
When the air comes down the other side, it becomes much drier and that means it ends up warmer.
The size and shape of a mountain, along with upstream wind speed, temperature and humidity, play a role in the amount of heat seen on the downwind side.
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A number of other factors can also help to increase the temperature on the downwind side of the mountain, such as air being pulled in from high above, vertical mixing of air at the top of the mountain, and radiative heating – due to sunnier conditions towards the mountain. of the wind. side.
The Foehn effect can be seen in mountainous regions around the world.
In areas where the impacts are greatest, they are given local names.
The Chinook affects the Rocky Mountains in North America, while the Zonda affects the Andes in South America.
According to the US National Weather Service, a Foehn event in 1972 caused the temperature in the US state of Montana to rise from -48ºC to 9ºC, an increase of 57ºC.
Rising temperatures can have detrimental effects, bringing the risk of avalanches, glacial melt, downstream floods and wildfires.
For the UK, the prevailing westerly wind means that the Scottish Highlands tend to see the most notable Foehn events.
One occurred in January this year, which allowed Achfary to reach a maximum of 19.9°Cprovisionally the UK’s highest temperature for January.
This story originally appeared on News.sky.com read the full story
