52.27191 -3.91597 Met Office CIMO Assessed Class 4 Installed 1/1/1955
Swyddffynnon weather station was originally installed in 1955. Temperature records have only been digitally archived from 1959 though manuscript copies for the first four years are available to view online. The site, however, is riddled with confusions that are not immediately obvious so here are my attempts at clarification.
To begin with I am baffled by the Met Office’s very low estimation of the site which warrants in depth investigation. Swyddffynnon has been “officially” assessed as the lowest regulated standard of Class 4 (Class 5 has no requirements to meet) and its consequent inaccuracy of +/-2°C. Looking at the 30 metre radius circled area below for Class 2 requirement the entire area is free from everything apart from pastureland and sheep.
Looking at Google Earth Pro historical imagery there are 8 aerial views going back to 1985 and they all look exactly the same in terms of site conditions with no changes whatsoever. This is actually not surprising given that the site owner of Cruglas Farm (incidentally the original name for this weather station) is well known in the Welsh Farming community for his efforts. Google AI has a “short” stating
“Cruglas Farm is owned by Terry Mills. He is also the owner of a beef and sheep farm and has been working to create a haven for wildlife on the farm for 30 years.”
He has also won awards for his countryside stewardship so this site is in very safe hands.
Moving on to the all important topography, again it is difficult to see any problems. The screen is at 171 metres amsl. A broad angle Ordnance Survey sheet of the area reveals nothing other than very gently undulating countryside with the screen neither in a frost hollow nor unduly high. The screen is 12 miles inland from the mid west Wales coast and 13 miles south west of Aberystwyth. The much higher ground of Mid Wales lies to the east of the screen so any winds passing over them would already be relatively dry easterlies. In the lee of these drier easterlies it is unlikely to create significant Foehn winds.
With absence of any artificial warming effects within 30 metres, consistent ground cover and benign topography typical of the wider area, I can see no reason for this site not to be Class 2 and fully accurate. Perhaps the Met Office knows something that I do not but I find it incredibly hard to believe this site is worse than Class 3 assessed Heathrow. Again I am finding sites that are rural and likely very reliable being marked down by the Met Office whilst all manner of corrupted urban or aviation sites are considered acceptable. Perhaps if Terry Mills surrounded it with Solar Panels it would improve its ratings! Clearly something is not right here.
Under its current custodianship the site has a very good observations record but its history prior to Terry Mills is a bit patchy. The original 1955 site was actually elsewhere but with no renaming of the site (just that covert renumbering hence two different District County Network Numbers I noted in the headline) it was not apparent where it was. The brief “Remarks” comment below identifies it.
The original site closed down in 1974 and was by the farm buildings below. These buildings post date the relocation so were probably the cause of the move.
Curiously there was then a big gap in the readings with none at all recorded for over 7 years until late 1981
The site then ran with fully reliable manual readings until automation took over but with a surprisingly long period of no readings from mid 2010 to late 2011 through the changeover. The site has run reliably ever since.
In conclusion, despite that frustrating transitional loss of readings in 2010/11 this site has been, in my opinion, very good for 44 years since relocation and was probably a good original location. This missing data unfortunately renders the site very difficult for long term historical climate reconstruction though could be a good comparator for more recent times. For the Met Office to regularly downrate such sites (South Newington for example) is very strange from the CIMO and meteorological viewpoints so perhaps there are, yet again, other motivations.
via Tallbloke’s Talkshop
July 20, 2025 at 08:02AM
Iowa Climate Science Education 