Wych Cross DCNN5456 – A demonstration of exposure changes over time.

51.06576 0.03289 No Known Met Office CIMO Classification Installed 1/6/1998 Closed 24/12/2021 Reopened: unspecified date.

Wych Cross weather station sits just off the A22 in the Ashdown Forest of East Sussex – an area often associated with A. A. Milne’s Hundred Acre Wood where Winnie the Pooh has a sign over his door reading “Mr Sanders House” – a distant relative of mine. It lies almost equidistant between Crowborough to the east and Crawley (Gatwick and Charlwood) to the west. The ongoing story of this site is one of significant exposure changes (akin to those exhibited at many sites most notably Slapton) along with continuing the animal theme including lots of llamas, pigs, deer and all manner of exotic fowl but no bears.

Originally installed in 1998 as a solely manual reporting weather station at 200 metres/ 656 feet amsl, the site was in a relatively open “High Weald” AONB location. Probably for the ease of observers the screen was set alongside a farm track-way and by a low level fence. At this stage this was a good open location, a long way from the main road and certainly not subject to any form of Urban Heating (UHI). Not perfect but able to well represent the surrounding area of rural south east England. Observations standards were reliable. It is the ensuing history of periodic non reporting then closure………then reopening and all the parts in between that are the issue.

Observations from the manual site ran from 1/6/1998 through to 31/12/2004 when they suddenly stopped. From 8/10/2010 readings restarted from an automatic station at the same location. These then stopped on the 24th December 2021 as shown below. This site did not appear on any subsequent online listings nor on my FOI requested list of CIMO ratings.

As Wych Cross just appeared to be yet another closed rural station, I had not previously opted to review the site. Then in February this year I noted this below. Wych Cross it would seem has yet again risen Phoenix-like from the ashes. It does not, however, appear on the Met Office list of operational stations though this could be due to their rather notorious failure to update their site very often.

Investigation revealed some dramatic changes over Wych Cross’s life – what started as farmland morphed into a tourist attraction and seemingly back again when the business failed due to the effects of Covid lockdown and the sad demise of the owner. The Forest Row Llama Park ran from around 2012 to 2021 during which time it developed into a significant tourist attraction.

One would not expect this agricultural to tourism conversion to be without effect. The once isolated screen was progressively built around with animal enclosures, pathways and a play area with the visiting public in regular attendance as well as the novel animals. This still below shows the screen centre image and is taken from a visitor’s “holiday” video they chose to post online. Again this is probably not too much of a problem aside from occasional motorised transport passing by.

What is a problem, however is that during the period of automatic reporting a large stable block of over 220 square metres/ 2400 square feet was built just a few metres to the immediate east-southeast of the screen. This would have altered winds from that direction whilst also forming a wall radiating back late afternoon heat.

This type of site alteration (similar to Slapton where a cricket pavilion came and went over the years) significantly alters the screen exposure and hence affects readings. The attendant human and livestock interactions and mechanised equipment further distort the consistency of readings over time. Presumably the weather station was shut down with the demise of the park (and apparent removal of the stabling) and access possibly restricted. The Met office opting to reopen the site is not a problem for ongoing meteorology, but what is a problem is trying to compile a historic temperature record (notoriously to the second decimal place of a degree) from a site with such a variable history.

Wych Cross is now unlikely to ever be a site recording artificially elevated daily maximums (though it may have in the past) but with the vestigial remains of the former use may well report slightly elevated overnight minimums which result in the same elevations to daily means. Overall whilst the site may now be acceptable (probably rated CIMO Class 3) its history is not of any climate reporting use.

Spot the Stevenson Screen?

Source: https://tallbloke.wordpress.com/2026/04/05/wych-cross-dcnn5456-a-demonstration-of-exposure-changes-over-time/