Measuring Rainfall

[Kevin Holohan]

I live in Milton Keynes, close to the place (Woburn) which was called out on the BBC national weather forecast on Monday this week as having had a month of rain in 2 hours.

Certainly we had several long periods of very heavy rain on both Sunday and Monday to break up the alomost continuous lighter rain. I left 2 buckets out in the garden after pruning and other jobs on Saturday. Different diameters but both had 175mm of water in them on Tuesday morning after the rain stopped. 

What is the likelyhood that this represents a reasonable estimate of the amount of rain we had on Sun and Mon?

[Graham Easterling]

It rather depends on the diameter of the bottom of the bucket relative to the diameter at the top. 

Without knowing the actual figures, and assuming they are a typical bucket shape I would guestimate at around 100mm of rainfall. Doesn't sound too unreasonable, from what I've read.

Graham

Penzance 

[Kevin Holohan]

Thanks Graham. 370mm top/270mm bottom. The bucket has now asccumulated 250mm rain (since Sunday) in it after another 13 hours of heavy rain. Number of villages around Milton Keynes and Bedford now cut off with roads flooded.

[Graham Easterling]

Using your bucket dimensions (and use of an online calculater!) I make your updated figures about 140mm of rain. An excetional amount for your location.

Graham

[Len]

I see Woburn's 30-yr average rainfall for September is 55 mm.

So over 55 mm in 2 hrs is heavy rain.

25 mm is an inch, so a rainfall rate of 1.1 inches per hour.

Typical of a slow moving weather system.

Thunderstorms can give more.

The quasi-stationary cumulonimbus in the Hampstead storm of 1975

gave 150 mm (6 inches) in 95 mins.

Len

Wembury