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Captain's Log

November 2015

Weather Forecasting

Turned Out Nice Again!

Turned Out Nice Again!

"I get all the news I need from the weather report," sang Paul Simon in his 1970s hit The Only Livin' Boy in New York. And although the song celebrated a care-free attitude, it summed up an interest that has preoccupied mankind since prehistoric times. For farmers, predicting the weather - when to sow and when to gather the harvest - were crucial to success. For fishermen, forecasting storms and high winds were not just what their livelihoods but their very lives depended on. 

Blue Sky Thinking
As far back as 650BC the Babylonians were studying cloud patterns in an attempt to work out what the weather was going to do. Three hundred years later Aristotle described weather patterns and how to predict them in his book Meteorologica. This contained some remarkably astute observations along with a significant number of errors. But a Curate's Egg is better than no egg at all and it remained the most authoritative work of its kind for almost 2000 years. It's also worth remembering that while Aristotle was applying logic and collecting empirical evidence, people in Northern Europe were convinced that thunder was caused by Thor bashing his anvil, and lighting was the sparks from his hammer. All good dramatic stuff, but as time went on a more scientific approach to weather forecasting began to gain ground. And this required instruments.


A renaissance in Forecasting
A window, for instance. The word comes from the Old Norse vindauga - literally 'wind eye' - an aperture through which our forebears could have a nervous squint at which way the wind was blowing. This was a start but more sophistication was required. A lot more. Humidity obviously affected the weather and around the middle of the 15th century the first hygrometer was invented. By whom is debatable. The general consensus is for the German Nicholas Cusa (c.1401-1464), but there is a school of thought in favour of Leonardo.


We know about today, what about tomorrow?
Most authorities agree that around 1592 Galileo designed and constructed a thermoscope. Twenty years later a calibrated scale was added so that changes in temperature - rather than just being indicated - could be measured: hence the new name thermometer. So far so good, but humidity and temperature tell us about the here and now. Forecasting or foretelling future weather conditions required something more. Cue Evangelista Torricelli. In 1643 he invented the barometer, was able to measure air pressure and could make a reasonable guess as to what the weather had in store. The rest as they say, is meteorological history. A time line of refinements and improvements from then until now. But with one or two interesting detours.


A storm in a Jam Jar
The storm glass is a classic example. It had been around since the 1750s but wasn't in common use until the 19th century. Developed by Admiral Robert FitzRoy and used aboard HMS Beagle on Charles Darwin's famous voyage, the storm glass or chemical barometer was and remains something of an enigma. It consists of a sealed glass jar containing a mixture of chemicals that undergo various changes and growths of crystals depending on the weather. Fascinating to watch and more than a little mysterious. Because after all this time, no one is exactly sure how it works. But then sometimes it doesn't. That's the thing about weather forecasting. Despite ever more precise instruments, sophisticated computer modelling and oceans of data, it isn't an exact science. Especially in an island nation like ours.


'What's the weather like where you are?'
In the American mid-west things are a lot simpler and have been so since the invention of the telegraph. When the weather bureau in Dead Dog, Dakota (or wherever) wanted to know what was coming up, they checked the wind direction and speed. Then they contacted a town at the appropriate compass point and asked about the weather. "Storm clouds heading towards you (distance 100 miles) at 20mph." Nine times out of ten, four hours later it would be coming down like stair rods.


Next week will be hot, dry and sunny (just like last week)
In North Africa weather prediction is even easier. Some years ago a clip was shown on TV of an Egyptian forecast. A large man in a suit slightly too small for him was sticking magnetic icons on a map of the country. There must have been about fifteen or twenty. And they were all little suns. But then 'hot and sunny' describes the weather in Egypt pretty succinctly - and for most of the year as well. The broadcasters could have saved a lot of time and money by simply making a recording and playing it every night. Perhaps they did.


Weather in Microcosm
Of course big countries have big weather - extremes of temperature, blizzards, and tornados. In the UK we have variety and conditions are often very localised. Which is why digital 'home weather stations' are so popular. Never mind what's going on ten or twenty miles away, these tell you what to expect right where you live. And if you're only really happy when you're gardening, walking, fishing or sailing - well that's the only news you need.

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