Rapid Temperature Change

12th January 2024

Today the inversion was even more striking. It was very noticeable both walking up and walking back down how quickly the temperature changed in a very short distance, it rose about 7°C in about 100 metres of walking when heading up the hill, and dropped again by a similar amount then I went back into the cloud on the way down. The inversion layer was rising through the day, from about 750 metres at around 10am, to about 1200 metres at 1pm. I also managed to check some of the minute by minute data from the Met Office Aonach Mor Weather Station, and it also saw a rapid drop in temperature as the inversion layer rose, at 12.45 it was reading +2.3°C, while five minute later at 12.50 it was down to -3.8°C.

A return to some more “normal” Scottish weather tomorrow with some overnight drizzle followed by a dry but cloud day.

Heading up the hill this morning the cloud was about 750 metres. It crept up through the day. 

Looking North-East with various hills poking out of the sea of cloud.

During the day the cloud level began to rise, and flow over the ridge of Carn Mor Dearg. Notice the sun reflecting of the snowpack on the left, in some areas the snowpack has a really hard and icy surface. 

The cold temperatures of late had caused the snow to facet in some locations. Facet is a form of weak crystal structure which has no cohesion, the grains are not well bonded to each other. On a crystal card they behave like sugar, many individual grains which are not stuck to each other. When buried facets form a weak layer, and throughout the world are a factor in many avalanche accidents.  Not a problem at the moment due to the particular snow set up we have (generally hard and icy or crusty). Whether or not these one will cause any issues going froward depends on what the weather does, and remains to be seen. However, it is something that we forecasters are keeping an eye on. 

A fog bow just as I was descending into the cloud.

Descending into the cloud, and the temperature dropped noticeable. I had my thermometer out on the way down, as I had felt this on the way up. I had stopped briefly just beyond the top to the tow, and the temperature had been about +3°C, where this picture was taken it had dropped to -3.7°C, a change of over 6°C in air temperature in about 50 metres!

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