Even Lower Humidity.
28th December 2025
It was another settled day in Lochaber. On the blog a couple of days ago the unusually low relative humidity was mentioned. Well today it got even lower, down to 3.1% according to the holfuy station. However, according to the met office mountain weather station (link here) it was down to 1%. A closer look at the raw data gave readings as low as 0.65%. I am not convinced this is correct, for comparison lowest reliably recorded relative humidity in the world was around 0.36% in Iran in June 2017 when the air temperature was very high (about 46°C).
I am also not sure the reason for the difference between the holfuy and met office stations. The met office station instruments are at the top of a 10 to 15 metre tower, while the holfuy station is on the side of the hut a couple of metres of the ground which could have an effect. Perhaps one (or both) are not very accurate these unusual conditions.
Although summit temperature were getting above freezing, the clear skies and low humidity meant that the snowpack is remaining very hard and icy. At lower levels temperatures are remaining below freezing all day. The only real change over the past few days is the amount of water ice that is forming on various damp hillsides.
Temperature and Relative humidity at the holfuy station over the past 5 days. Both have been up and down a fair bit, with high humidity associated with the approaching cloud yesterday being visible, and the very low values of Relative Humidity today.
Nice light when looking South at 10.30am. The thin high cloud and low sun producing some nice light. It was not as dark as the foreground suggests.
The LHS of Coire nan Lochan of Aonach Mor
Looking back as the sun hits the crags on the RHS of the coire.
Aonach Beag
Water ice on hillside makes for a slip hazard. I once saw someone slip on a patch of ice such as this, they picked up speed very quickly but fortunately didn’t hit any rock when they shot of the end onto the heather.
Mountain streams are starting to get choked up with ice.
Reflections in the frozen loch in Coire nan Lochan.
Patterns in ice left high and dry as the water level of the loch has slowly dropped since it initially froze a few day ago.
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