It has been quite an interesting day of weather across Scotland, not that you would notice without carefully watching the hourly SYNOP observations from our mountain stations. I still can’t quite believe what I saw – and a sensor malfunction could well be the cause – but the temperature dropped from 7.3°C to 0.0°C between 16 UTC and 17 UTC at the Cairnwell. The previous hour the dewpoint there was -9.9°C and the wind was blowing 250° at 45 knots above the inversion. That fell back to 220° 15 knots as the inversion rose above 3,000 feet, and at 18 UTC the temperature fell back once again to -0.8°C, so now we also have a sub-freezing layer in what must be a very sharp inversion indeed. It’s a shame the Met Office closed Shanwell just when you could do with an 18 UTC ascent from their. Meanwhile the Cairngorm and Aonach Mor SIESAWS still lie above the inversion, with temperatures of 8.1°C and 3.8°C, and dewpoints of -5.0°C and -13.3°C respectively. The gradient is tightening ahead of the cold front with means speeds of 49 knots and gusts to 61 knots at Aonach Mor.