Weather Predicition from Observation of Cloudlets

Abstract

I FEAR Mr. Cave (NATURE, November 21, p. 749) misunderstands me, or I him. He controverts none of my facts, and his own are indisputable. Thus, though I, with amateurish powers of observation, find it difficult, no matter how long I watch, to perceive the waxing, and waning, of a cloud, I have always thought it probable that a thick or extensive mass, if exposed on opposite sides to unlike weather conditions (e.g. sun-heat), may condense at one extremity while dissolving at another. Also I know that the tendency is, on the whole, one way or the other. Again, I know that in our changeable climate, indeed in any climate, a waxing cloud does not necessarily imply rain; it may not condense sufficiently. Nor does a waning cloud imply fine weather; it may cease to wane. Nevertheless, “when clouds are seen wise men put on their cloaks”, and exceptions do not disprove the rule. They should merely direct attention to modifying circumstances—for example, to the variations of the barometer, the season of the year, the time of the day, the direction of the wind, and the colour of the sky. Whatever the modifying circumstances, it remains true that rain cannot come unless rainless clouds condense, or fine weather unless raining clouds dissolve. For most people, even I suppose for the weather expert, observation of this gathering, or breaking, of clouds is the most employed quick method of weather prediction.