Weather Prediction from Observations of Cloudlets

Abstract

I DO not think that the method described by Sir G. Archdall Reid in NATURE of November 7, p. 676, is at all of universal application. It certainly cannot be applied to cirro-cumulus; the cloudlets composing lenticular cirro-cumulus not only may wax at one end of the cloud and wane at the other, as mentioned by Sir G. Archdall Reid, but they always behave in this way; I do not think that any of the explanations he gives accounts for the phenomenon, but the point is not to account for it, but to decide whether the waxing or the waning of the cloudlets is to be taken account of in weather prediction. Again, a whole mass of cirro-cumulus cloudlets may form and disappear in a very short time; is the appearance or the disappearance to be reckoned with? The lower clouds seem to me to tell even more against the method; on almost every fine summer morning we may watch cloudlets waxing, but it by no means follows that rain will result; probably in nine cases out of ten it will not. I should imagine that there must be nearly a hundred days every year when the method is disproved by the waxing of cloudlets which will develop not into rain clouds, but into the cumulus of a fine day.