CLOUDBURSTS

Cromwell Argus, Volume LXI, Issue 3168, 22 June 1931, Page 5

CLOUDBURSTS

A cloudburst' to an excessively Heavy local downpour of rain, of com* paratlveiy brief duration. In its Intensity and .its concentration in space and time, it bears much the same relation to a widespread heavy rainstorm as does a tornado to an ordinary cyclonic storm (says C. F. Talman In

Popular Mechanics"). The name of the phenomenon Is popular rather than scientific, and no hard-and-fast definition of this name has ever been adopted.

Of course, we know to-day that a cloud Is merely a collection of very fine droplets and not a coherent mass, such as might be subject to any pro* cess of rupture. Moreover, modern research has revealed the fact that the clouds contain surprisingly little water. The very densest clouds are probably not more than one part water to 30.000 parts air. and It to computed that. If a huge thundercloud several miles in depth were, througn a miracle, precipitated en masse to the ground at the maximum speed of falling rain, the resulting rainfall would be decidedly less intense than often occurs In so-called cloud-bursts. One of the fastest showers ever measured with an automatic rain gauge was that of May 1. 1908. at Porto Belle, on the Isthmus of Panama, In which 2.47 inches fell in three minutes. This rate of fall was surpassed on April 6, 1926, at Opld's Camp, in the San Gabriel mountains of California, when 1.02 inches of rain—equivalent to 116 tons of water per acre—fell In one minute. This remarkable downpour was caught by two automatically recording gauges, standing side by side, and as their records agreed, the figure just quoted is entirely trustworthy. While this figure stands, for the time being, as a world record so far as actual measurements go, It certainly does not represent the greatest possible intensity of rainfall In a cloudburst. Evidence of much more excessive fails is supplied by the huge holes, known as "cloudburst cavities." found after cloudbursts at places where they were evidently produced by the direct impact of the falling water and not by rapid run-off from some adjacent area. Observers have described these cavities in some cases as resembling the work of the hydraulic "giant" used by gold miners.