It is also shown by the Challenger observations that on the open sea the greatest number of thunder-storms occur from 10 P.M. to 8 A.M. And, from this, Dr. Buchan concludes that over the ocean terrestrial radiation is more powerful than solar radiation in causing those vertical disturbances in the equilibrium of the atmosphere which give rise to the thunder-storm.
CHAPTER XXXV
WEATHER-FORECASTING
To foretell with any degree of certainty the state of the weather for twenty-four hours is of immense advantage to business men, tourists, fishermen, and many others. The weather is everybody’s business. And the probabilities of accurate forecasts are so improving that all are more or less giving attention to the morning meteorological reports.
Weather-forecasting depends on the principle from vast experience that, if one event happens, a second is likely to follow. According to the extent and accuracy of the data, will be the strength of the probability of correct forecasts. And the great end of popular meteorology is to demonstrate this.
We have given some explanations of the weather in some respects unique; and a careful consideration of these explanations will the more convince the reader of the importance of the subject. No doubt the changes of the weather are extremely complex, at times baffling; and the wonder is that forecasts come so near the truth.
For instance, the year 1903 almost defied the ordinary rules of weather, for it broke the record for rainfall. And, last year, so repulsive and unseasonable was the spring, that there seemed to be a virtual “withdrawal” of the season. I wrote on it as “The Recession of Spring.” Speak about Borrowing Days! We had the equinoctial gales of March about the middle of April. On very few days had we “clear shining to cheer us after rain,” for the bitter cold dried up any genial moisture. An old farmer remarked that “We’re gaun ower faur North.” No one could account for the backwardness of the season. Unless for the cheering songs of the grove-charmers, one would have forgotten the time of the year.
In March of this year, at Strathmore, the barometer fell from 30·5 inches (the highest for years) to 28·65 in five days without unfavourable weather following. It again rose to 30·05, then fell to 28·45, followed by a rise to 28·7 without any peculiar change. But in two days it fell to 28·4 (the lowest for years), followed by a deluge of rain and a perfect hurricane for several hours, while the temperature was fortunately mild. It was only evident at the end that this universal storm had been “brewing” some days before.
All are familiar with the ordinary prognostics of good and bad weather. A “broch” round the moon, in her troubled heaven, indicates a storm of rain or wind. When the dark crimson sun in the evening throws a brilliant bronzed light on the gables and dead leaves, we are sure that there is an intense radiation from the earth to form dew, or even hoar-frost.