On Sunday, September 4, 2016 at 12:43:00 PM UTC+1, xmetman wrote:
On Sunday, 4 September 2016 12:02:41 UTC+1, Graham Easterling wrote:
On Sunday, September 4, 2016 at 11:19:53 AM UTC+1, xmetman wrote:
On Sunday, 4 September 2016 10:53:47 UTC+1, vidcapper wrote:
You might find this interesting, if a little out-of-date.

http://maps.nls.uk/geo/explore/#zoom...ers=10rain&b=1

You can switch between the old rainfall map & the modern one by using
the 'change transparency of overlay' slider.

I finally know why Capil Curig is so wet!


--

Paul Hyett, Cheltenham

Paul

I knew about this site, but had never noticed the 1881-1915 rainfall overlay.

Of course this begs the question if we have rainfall data to produce such a detailed map as this why do the Met Office only have a gridded data series that extends back to 1910?

Bruce.

A detailed map doesn't necessarily equate to accuracy. The MetO produce detailed actual and anomaly maps each month, showing rainfall in great detail over west Cornwall for instance. But where are the actual rainfall reports from? just Camborne & Culdrose. This can lead to some highly inaccurate maps, especially in summer. It was the extreme inaccuracy of these maps a few years back, that led me to realising Scilly was double recording rainfall. It still took them nearly 6 months from the time I reported it to correct it. The only reply I ever got was an unofficial private one, giving the reasons for the problem, in some detail - it was both interesting and disturbing (total lack of any reasonableness checks). I never got an official response.

It meant that the 'actual' figure for the Penzance area, presumably computed in some way from the Camborne & Scilly figures and a relief map, was 30% or so high for several months.

Graham
Penzance

Graham

I don't know if there are any MO climatological sites or Environment Agency gauges down in your part of Cornwall?

The EA have a better network of automatic gauges across the country used to monitor rivers that we never get to see. I seem to remember there was one above Boscastle. A map of their locations would be handy so that you could ask to get archived rainfall data from one of them, but I've never seen one so perhaps I'll ask them.

As regards for that 1881-1915 which must have used rainfall data from the Symon's British Rainfall organisation I've just looked at the 1872 annual edition and it lists dozens of rainfall stations across west Devon and probably far more that they are now (excluding WOW of course).

http://www.metoffice.gov.uk/media/pdf/t/s/Symons's_British_Rainfall_1872.pdf

Bruce.

Good point about EA stations. There's certainly one at Drift Dam, 2 miles WNW of Penzance. They also had one at Porthcurno, though I'm not sure if it still exists. They also have a gauge at Stithians, on the Lizard peninsula, not far from (but wetter than) Falmouth.

They have one near Boscastle. There were 2 similar floods at Boscastle in the 1950s, 1 affected a nearby gauge, the other didn't. I've seen photos from the river level in both floods, it was very similar. Because there's no reliable rainfall figure for 1 event, many more recent accounts of Boscastle 1950s floods incorrectly combine the 2 events into 1, it's become a forgotten flood.

In fact, Boscastle has been flooded severely many times. The most recent 1957, 1958, 1963 (all June) & 2004. The 2004 did most damage largely because of the cars being swept into bridges from the nice new NT rapid runoff car park on the flood plain. In 2004 204mm was recorded at Otterham - around 5 miles from Boscastle, and 184mm at Lesneweth, a bit further way. Incredible the EA were quite happy with the car park remaining, saying the flood was a once in 200 years event, I think they included an extra nought. Stephen Burt wrote a very good paper on the Boscastle 2004 flood, and put it into a much better historical perspective.

These north coast storms are far from uncommon, normally just to the east of headlands, which I think is typically down to 3 way convergence (sea breezes from north & west, against a gradient S wind. I've experienced a couple of storm that have dropped 100m or so in a short space of time. Here's an account of 1 http://www.turnstone-cottage.co.uk/SrMerrynStorm.PDF Once again June, the favoured month.

It's a real shame that we are loosing more and more reporting stations. So many WOW stations are innacurate and are in no way a replacement.

Graham
Penzance