Inversion

Inversions are quite common in anticyclonic conditions, and there’s been one in the last week across the UKUK The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and Northern Ireland. where an intense anticyclone (1046 hPahPa A Hectopascal is the SI unit of pressure and identical to the Millibar) has been meandering across northern Scotland for much of that time. Yesterday (11 January 2024) the inversion lowered to ~3,000 feet across Scotland to allow the Munro’s to peek above it. This morning the dew pointDew point The dew point is the temperature to which air must be cooled to become saturated with water vapor, assuming constant air pressure and water content. on Aonach Mor (1130 M and just to the south of Ben Nevis) dropped to -34°C and the humidity to ~5% which is extremely low and doesn’t happen that often.

Further east in the Cairngorms a similar thing happened on CairngormCairn Gorm Cairn Gorm (Scottish Gaelic: An Càrn Gorm) is a mountain in the Scottish Highlands. It is part of the Cairngorms range and wider Grampian Mountains. With a summit elevation of 1,245 m (4,085 ft) above sea level, Cairn Gorm is classed as a Munro and is the seventh-highest mountain in the British Isles. itself. The thermographs below are for Cairngorm itself (1245 M) and the AWSAWS Automatic Weather Station on the edge of Aviemore (220 M) in the Strathspey. Despite the low stratus at Aviemore temperatures still fell close to -4°C, whilst on the tops it was a relatively balmy 4°C.

Above and below the inversion, from the Ptarmigan Restaurant and Loch Morlich.

Many years ago as an observer at RAF Kinloss I remember contacting Rob McElwee at the the BBCBBC The British Broadcasting Corporation (BBC) is the national broadcaster of the United Kingdom, based at Broadcasting House in London. It is the world's oldest national broadcaster, and the largest broadcaster in the world by number of employees, employing over 22,000 staff in total, of whom approximately 19,000 are in public-sector broadcasting. (I can’t for the life of me remember how I did this, I must have phoned) to alert him to the fact that we had spent that day walking on Cairngorm and the northern corries in warm sunshine above the inversion. He managed to show a visible satellite image of the UK in his evening forecast (9.25 pm?) that showed the only bit of high ground peeking above a sea of low cloud covering the UK was the northern Cairngorms, good old Rob McElwee!