Lake Vyrnwy & Lake Vyrnwy no 2 – How it should be done.

Lake Vyrnwy 1 (DCNN 7947) 52.75794 -3.46040 No CIMO Assessment (Probably Class 2) Installed 1/1/1940 Data ends 30/6/1985 but site still believed to be operational. Lake Vyrnwy No 2 (WMO 03410) 52..75717 -3.46540 Met Office CIMO Assessed Class 1 Installed 1/1/1988

Lake Vyrnwy is a perfect example of how climate reporting weather stations should be sited and operated. Its predecessor, the original site, was also run in an equally exemplary manner. This is a good story of what should be the norm rather than the exception.

To put the longer term history of the area in context, it is worth reviewing both sites. Firstly the original manual reporting site would probably have been rated as Class 2 from the encircled 30 metre area below. It is worth noting that the aerial view is from 2024, this screen and enclosure still appears in situ 40 years after “closure”. This is not untypical, as for example was shown at Herstmonceux. The oldest aerial image on Google maps 2002 indicates the hedge to the north was a minimal height and unlikely to be a major influence.

The readings record was impeccable with virtually no missed readings throughout its entire 45 operating years. Bearing in mind that it is a considerable walk from the nearest road and for those who remember the exceptionally severe winter of 1962 consider the effort that the following readings must have entailed with no omissions whatsoever.

The readings taken at 09:00 would have almost always been toward the minimum readings – 10 degrees below freezing in breezy open conditions with probably deep lying snow certainly showed dedication to the cause – different times.

I have no idea why a new station was opted for but clearly a lot of thought went into ensuring the site quality was not degraded and indeed improved upon. A former Met Office manager who “guest posted” the article on metrology divulged to me that the conditions for new weather station sitings back in the 70s/80s (he had personally established Dunstaffnage) were very strict indeed. Standards subsequently lapsed into the modern “anything goes” with Class 5 stations being installed even now.

The above image delineates the 100 metre radius from Lake Vyrnwy No 2. The site is flat and not intruded upon by any artificial effects. Readings are automated and, as would be expected for such a fully equipped site, are infallible.

When Tim channon reviewed this site there appeared to be a certain amount of uncertainty over ground cover, however, I do feel that is rather nit picking and the pastureland setting is certainly representative of this part of mid Wales. The actual Lake itself is an artificial construction built (controversially at the time) in the 1880s by the Liverpool Corporation Water Works to supply fresh water to the city. Bodies of water, if not typical of the region, can be classed as having detrimental effects but I have no doubt this will not be of any influence in the readings given the lake is not even visible even in the wide angle views. The nearest point of the Lake is over 750 metres away.

Lake Vyrnwy weather stations are certainly ones which are acceptable for inclusion in the historic national temperature record. In stark contrast I reviewed Llanwddyn:Cwm Cownwy at under a kilometre away which ranks as a totally unacceptable shambles of a weather station and yet equally gets its risible data included in the record. Compare this 21st century manual reading dedication (NA) in a balmy May 2022 at Llanwddyn:Cwm Cownwy to the 1963 Lake Vyrnwy dedication.

The Met Office has some very good weather stations but sadly seems intent on diluting quality with a large quantity of poor standard locations and reporting. Lake Vyrnwy will be included in my future temperature reconstruction.

Source: https://tallbloke.wordpress.com/2025/04/08/lake-vyrnwy-lake-vyrnwy-no-2-how-it-should-be-done/