Page:Handbook of Meteorology.djvu/111

 as this track covers a region of great moisture, the rainfall is apt to be very heavy—sometimes more than 3 inches.

The severest cyclonic storms are the West Indian hurricanes and the typhoons of the China coast. Throughout their courses they move through regions of very moist air. In these storms, the velocity of the wind results from a very rapid up-draught. The precipitation, therefore, is excessive. In the vicinity of the Gulf Coast of the United States, from 8 to 10

Bentley photo.

In the United States, cyclonic storms are more characteristic of winter than of summer weather; they are therefore usually described as winter storms. The precipitation may consist of rain, sleet or snow—rarely, if ever, of hail.

Snow.—When condensation below 32° F (0° C) occurs, the precipitation takes the form of the ice crystals popularly known as snowflakes. They form in almost infinite variety, but they may usually be classified as tabular (disk-shaped) or