Arran field course – live blog – Tuesday 7th September

Today’s activity for all groups was an instrumented walk up Goat Fell (850m above sea level) the highest point on Arran. We left the field centre with some trepidation, expecting heavy rainfall all day. Rain began for us around 2300 local time last night as the occluded front associated with the complex low to our west passed over. A sounding through the front from Castor Bay is shown below:

Castor Bay Sounding

Unfortunately, our automatic weather station crashed overnight, so we were unable to record the total rainfall as the front passed, but by comparing to other local stations we can estimate a relatively large accumulation around 25mm in common with other strong accumulations associated with the front (particularly over Ireland). The strong winds we experienced yesterday dropped over the course of the day and were a more reasonable 10m/s as the front passed.

Met Station Mon

As we walked up the hill we entered cloud around 500m and spent most of our walk in cloud with some local precipitation falling, likely enhanced by the hill. We arrived at the summit around 1pm local time. On our descent, the front passed and cloud base lifted leaving scattered cumulus and sunshine by late afternoon when we arrived back at sea level.

At the Summit

Back at the field centre, the automatic weather station recorded precipitation stopped around local midday and winds remained moderately strong throughout the day.

Met Station Mon

Tomorrow, I’ll post results from our first radiosonde (released today at 12Z) and first observations from our 15m mast. Following a science proposal competition, the students decided to launch our only ozonesonde tomorrow at 12Z.

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