Who is better at predicting the weather
Thursday, 29 August 2013

Dave’s Nose vs The Met Office

Who is better at predicting the weather: the might of the Met Office or a 73-year-old amateur with a keen sense of smell?

It’s been a summer that no one saw coming… or did they? When it comes to predicting the weather, who has the upper hand: the might of the Met Office or one man and his nose? And what’s coming around the corner?

CONTENDERS

Helen Chivers: a forecaster based in the Met Office’s HQ in Exeter.
David King: aged 73, a retired Met police officer and keen amateur weatherman based in Kent.

RESOURCES

Met: There are people all around the world taking measurements of temperature, humidity, wind, cloud cover and pressure. We have instruments on ships and buoys in the ocean, and all of the commercial aircraft around the world send back data every minute during their flights. There are nine geostationary satellites 36,000km above the ground providing total coverage of the Earth all the time, sending pictures every 15 minutes.

King: A Stevenson screen in my back garden with a maximum, minimum and standard thermometer, two Gemini – that’s a firm in Chichester – data loggers that measure temperature and humidity down to 0.2 of a degree, and finally two sun recorders on the roof. Everything is certified every year to Met Office standards. My office is rural. I leave home and within 300 yards I’m in open fields that stretch for 20 miles.

METHOD

Met: All the information goes into a supercomputer that simulates how the atmosphere works. The model itself is a set of mathematical equations and physics, including Boyle’s law, the gas laws and Newton’s laws of motion. We divide the globe into 25km squares, calculating what the pressure, wind, humidity and temperature is at 70 levels in the atmosphere, from ground level into the stratosphere and 30 levels down into the ocean as well.

From there we can work out cloud cover and whether it will be raining or sunny, and in just an hour the supercomputer can perform a simulation of what it will do for five days ahead for the whole globe.

King: Each morning I open the door and sniff the weather. When you get used to it you can work out what it’s going to do. I sat down one day and thought: how did our forefathers go about predicting the weather? I hit the cathedral records in Canterbury and Rochester and I found two wonderful moon charts. If the monks used these, they must have experimented with them. I sat with them for 12 years just seeing how good they were, and by golly they were good. It splits the day into two-hour sessions, then it splits summer and winter. I have a problem about April time because we slip into BST , but I’ve overcome that over the years by putting in ‘changeable’. People may think it’s cheating but it’s being practical.

WHO NEEDS A WEATHER MAN TO KNOW WHICH WAY THE WIND BLOWS?

Met: If you’re presenting a TV forecast you might look at whether it will rain tomorrow and at what time. If you were providing a forecast for aviation, say for what the winds are at cruising height of 35,000ft, you’d be looking at a different element in the forecasting process. Farmers might want to know when they’ll get five days’ dry weather to make hay.

King: We’ve got lots of vineyards down here so the farmers look at it, as do horticulturists, garden centres and flower sellers. It goes by word of mouth. Mum wants to know, if she puts the washing out on Monday, whether it’ll dry. That’s what you must aim for. I don’t have any qualifications, and people say it’s a lot of hocus pocus, but it doesn’t bother me. They had no scientific facts in the 1300s and we survived.

LONG-TERM FORECASTS

Met: Our forecasts are accurate within two degrees 90 per cent of the time. Technology and our knowledge of how the atmosphere works means that our four-day forecast is as accurate as our one-day forecast was 40 years ago. After five days, because of the variability of the weather and chaos theory, detail gets a bit more difficult. No one will ever be able to forecast the weather accurately 100 per cent of the time but we’re getting close to 80-90 per cent, which is a real achievement when you’ve got a very small island squashed between a big ocean and an even bigger continent.

King: Long-term forecasts are where I might very well have the drop. If the grass is growing on New Year’s Day, you’re only going to get one hay harvest. The first reference I’ve found for that is 1300. I tested it for 10 years and I said six months ahead that the third week of June and the first week of July would be dry, hot, sunny and calm for the hay harvest and – kapow – what’s it been? The Met Office has nothing like that, have they?

A fair moon means dry and sunny with no wind. From 6 to 11 August we had some dampness and then went into a really hot period from 11 to 15 August. After that it went downhill fast. There will be an easterly wind on 29 September – that’s a marker for a cold winter because that will blow through until 21 December. It’ll start snowing on Boxing Day and will still be there at Easter, four months later.

RED SKY AT NIGHT... THE SCIENTIFIC PROVERB

Met: Red sky at night is to do with light being refracted in the atmosphere. Usually we see the blue part of the spectrum, which is why the sky is blue, but when a weather system is moving away from the UK, light from the sun setting in the west bounces off the clouds, so the weather coming the next day will be fine.

Equally if you’ve got a system coming from the west and the sun’s rising in the east, the rays will be bouncing off these clouds, turning them red, and could be heralding rain in the next 12 hours.

A lot of proverbs to do with clouds have a scientific basis and come about through our seafaring heritage. Some of the others, perhaps in relation to berries in bushes, are less reliable. You get a good crop of wheat because of the weather that’s been, rather than the weather that’s coming. It’s all a response to nature.


David King’s guide to spotting the signs of a long, hard winter…


Take note of the wind direction on the four quarter days: 21 March, 24 June, 29 September and 21 December. That will be the predominant wind direction for the next 90 days. It’s very, very accurate.

Where the wind blows on St Martin’s Day (11 November) will tell you how warm or cold winter will be. Last year it was southwesterly and we had a very mild winter.

If it’s going to be a hard winter, the robin will come and park himself on your back door in the second week of September. That’s where you shake the tablecloth, that’s where the food is and he stakes his territory. Last year he didn’t have to, but this year he will.

Last year nature decided robins didn’t need any acorns but this year there’s millions on the trees. The leaves give protection to the birds and the acorns provide food.

Last year there were no stinging nettles, but this year there’ll be loads of them. Nettles, the robin and the acorn are the three absolute bankers for a cold, hard winter. You will see all of these, I can assure you


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