Dinorwic No 2 DCNN 7747 – Readings in the undergrowth and strange statistics.

53.14263 -410815 Met office CIMO Assessed Class 5 Installed 1/1/92

Dinorwig (Dinorwic) is most famous for its Pumped Storage Hydro electricity plant (one of the World’s largest) also known as “Electric Mountain“. At current prices it is estimated the PSH plant cost over £2 billion to construct. The weather station of the same name is certainly not anything like as grandiose, in fact it rather vies with Llanwddyn:Cwm Cownwy for being the cheapest and most basic site the Met Office could manage. Should that be a problem? After all temperature readings are a fairly basic observation practise.

This is what the site looked like from Google street view images back in 2010.

A back garden site on sloping ground with no perimeter fencing. Clearly not a great site but probably well cared for by its likely amateur meteorologist custodian. But that was 14 years ago and this is the 2024 image from the same viewpoint below.

Every image, from every angle indicates a site so overgrown that only the pole mounted anemometer is visible – just. The Met Office inspects sites on a regular basis and must be aware that this station cannot be recording accurate figures. To simply categorise the site as CIMO Class 5 (inaccuracy due to siting up to 5°C) whilst claiming (by their own ill defined rating system) it is ” Satisfactory” is beyond any reasonable level of acceptability. I am confident though that should this site break some obscure record it would be suitably broadcast regardless.

Further research into the surrounding area of North Wales reveals a strange distribution of weather stations and statistical representation. Dinorwic itself is just 8 miles from another weather station at Capel Curig which itself is only 4 miles from Betws-y-Coed. In this relatively small geographic section of North Wales there are 17 currently operational CIMO assessed weather station sites. Whilst I have no objections at all to numerous sites (providing they are of good enough quality) the national distribution of “climate reporting” sites should be reasonably equal to be genuinely representative in terms of the historic temperature record. There certainly seems to be disproportionately more recording stations in some areas (notably west London) than others such as east central Scotland.

It is worth noting these sites with opening date and CIMO classification – Aberdaron Class 4 from 1993, Alwen 5/1959, Arthog 4/1988, Bala 4/1939, Betwys-y-Coed 5S/1976, Capel Curig 2/1993, Colwyn Bay 4/1929, Dinorwic 4/1992, Hawarden Airport 4/1944, Lake Vyrnwy No 2 1/1988, Llanarmon Deffryn Ceirog 1956/5, Llanwddyn Cwm Cownwy 5/1988, Mona 2/2009, Porthmadog 4/1993, Prestatyn 4/1932, Rhyl 5/1986, Valley 3/1930.

Typical of most Met Office weather stations, the above indicates multiple low rated poor sites with five Class 5, eight Class 4, one Class 3, two Class 2 and just one at Class 1. However, with such concentrated area cover the Met Office still feels the need to estimate “Clmate Averages” for sites long closed.

From https://www.metoffice.gov.uk/research/climate/maps-and-data/uk-climate-averages comes the map extract below. {N.B. These Met Office maps are in no way geographically correct for locations}

The three stations below the marked and named Capel Curig station are Llanbedr which was closed down in 2004, Cwmystradllyn a rain gauge only site which stopped temperature readings in 1982 and astonishingly LLanfairfechan which originally opened as far back as 1880 but closed down in 1956. The data offered online for Llanfairfechan becomes even more bizarre as below.

Despite marking Llanfairfechan on the guide map and then heading the data page similarly, it refers to data for a different station – Aber No 2. If that is not puzzling enough then this really makes the matter confusing…..

Aber No 2 station itself closed in 2002.

In conclusion Dinorwic No 2 is a poorly sited and maintained, low quality (cheap?) manual reporting weather station in close proximity to many other often equally poor sites. Its data is fed into a system that formulates (for inexplicable reasons) theoretical averages for other no longer existing weather stations that may, or may not, be in locations very poorly indicated on a modern internet page.

Back in 2012 the original author of the Surface Stations Project – the late Tim Channon – said this in his early introduction. “One of the things becoming apparent is how many people have assumed sites are competent without really knowing.”  i would like to add that people have also assumed that the stations actually exist when, literally, hundreds do not.

Source: https://tallbloke.wordpress.com/2024/11/11/dinorwic-no-2-dcnn-7747-readings-in-the-undergrowth-and-strange-statistics/