How hard did it rain last week?

Hardcore Protonistas – and that’s you if you are reading this – will know that I love measuring things.

I love the way that measurements allow an extra level of wonder at the intricate detail of the world around us.

The rate of rainfall at NPL Teddington on 14th August 2014. The rainfall rate initially exceed 100 mm per hour. The first event resulted in 28 mm of rain and the second 18 mm of rain.

The rate of rainfall at NPL Teddington on 14th August 2014. The rainfall rate initially exceed 100 mm per hour. The first event resulted in 29.3 mm of rain and the second 18.4 mm of rain.

Last Thursday 14 August 2014 there were two torrential rain events at NPL.

They were kind of event that makes you stop what you are doing, go to the window and just stare. Personally they evoked memories of my childhood home and the security of being indoors and protected.

All very nice. But how much rain fell? And was it exceptional? These questions can only be answered by looking at data.

So I downloaded data from a weather station on the roof of one of NPL’s buildings. The graph at the top of the page shows the key features of the data.

  • In both events the rate of rainfall was initially over 100 millimetres per hour
  • The first event deposited 29.3 mm of rain and the second 18.4 mm of rain.

These data show that these were indeed powerful weather events.

Over the main NPL site, which comprises approximately 400 m  x 100 m = 40,000 square metres, the first event result in the deposition of approximately 1160 tonnes of water in approximately 50 minutes. Wow!

But were the events exceptional? The Met Office keep a record of extreme weather events (Link) which states that the most extreme UK rainfall events have been:

  • Highest 5-minute total: 32 mm on 10 August 1893 Preston (Lancashire)
  • Highest 30-minute total: 80 mm on 26 June 1953 Eskdalemuir (Dumfries & Galloway)
  • Highest 60-minute total: 92 mm on 12 July 1901 Maidenhead (Berkshire)

Assuming these historic measurements are indeed reliable – which is not always the case – then the events in Teddington last week  were not technically ‘extreme’.

However they were astounding – and in the very best sense of the word – wonder-ful.

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3 Responses to “How hard did it rain last week?”

  1. teddnet Says:

    Perhaps those of us who are attracted to Protons for Breakfast are ‘Breakfast Electrons’?
    I remember the warm rains of typhoons in Hong Kong- when the air turned nearly opaque and you could open your mouth to the sky and (nearly) drink.

  2. protonsforbreakfast Says:

    Mmmm. Breakfast Electrons ? I see the logic but somehow it doesn’t seem respectful enough. I have just been learning about why the rainfall has those ‘spikes’ and what you can tell from them – and that it (I think) different from Typhoons. But from your description it sounds spectacular.

    I hope you enjoy your last week of ‘holiday’. All the best M

  3. Suzanne Doyle Says:

    I envy you this rain! We’ve been getting a little drizzle here in California but probably won’t get real rain until October.
    Suzanne

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