Nick Whitelegg wrote:

I went there last summer (the Saturday of the August bank holiday
weekend) and equally bizarre and unexpected weather occurred, so maybe
it's just the topography of the area.

Most air masses generally approach from the west and Mynydd Du is the
first real bit of high land that they reach, thus the air is forced
upwards, cloud forms, rain falls. I suspect that more rain falls on
Mynydd Du than on the eastern side of the Beacons because of this. I've
often seen clouds on Mynydd Du but sunshine further west.

Same thing happens on Gower, a flattish peninsula stretching out in the
Bristol Channel. Often bathed in bright sunshine while clouds tend to
develop over the slightly hillier Swansea. Not uncommon for it to rain
in Swansea whilst sunny in Gower. I've often seen showers marching
along the Llanelli coast to the north completely bypassing Gower.

Paul
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