Barnes-Botany.co.uk

Welcome to my weather pages!

Circumzenithal arc

By following the links in the left side-bar, you can find some basic details of the weather recorded at my home in mid-Wales. This area is sparsely populated and relatively few weather records are easily available. As so often with areas of great natural beauty, it is primarily an agricultural community. It also has a loyal following of visitors from within Britain and from further afield: this part of Wales is one of the best-kept secrets of discriminating tourists. My daily weather records go back to the beginning of 1995, and I am happy to dig out historical data on request.

To the local community, to actual and potential tourists and to weather buffs, therefore, these pages may be of interest.

The image to the right shows an unusual optical phenomenon known as a circumzenithal arc or CZA. Associated with high ice clouds like the cirrus show here, it results from refraction within horizontally aligned ice crystals. This example, photographed on 26th October 2011 at my home (and replacing a poorer one shot on 7th February 2007), was about 65 degrees above the horizon, and shows vivid segment of what has been described by Gavin Pretor-Pinney as 'a smile in the sky'. Gavin set up the Cloud Appreciation Society, whose website includes a gallery of fine cloud and sky photographs. A detailed explanation of this and other optical phenomena can be found at the Atmospheric Optics website. the photograph here is straight from teh camera, with no enhancement of saturation - it really was this vivid!

Setting the scene

Setting the scene

Alltgoch lies in hilly country, with higher land to the north, east and west, and a clear view down the valley of the small Afon Aeron, which flows between steep, wooded banks about 20m lower than the house. The view above is from the hillside across the river, looking up-stream. The house has an Ordnance Survey benchmark indicating its altitude as 137m. As so often in hill country, the weather can vary dramatically within a very small distance, and you should bear this in mind when using these figures.

My ‘weather station’ is definitely not of a professional standard, but uses either good quality commercial instruments or home-made ones. In January 2004, I replaced most of my old set-up with a electronic system, but retain a manual set-up in parallel.

Observations are taken at 0900 GMT, or as close to that time as possible.

Location: north of the village of Llangeitho, Ceredigion,
at 52.24 deg. N., 4.01 deg. W.

One weather site of special local interest is John Mason's severe weather photography. This is a collection of wonderful photographs of storms and other weather events in mid-Wales recorded by a Machynlleth-based storm-chaser. There is also much of interest to read.