THE NATURE OF SLEET AND HOW IT IS FORMED

Abstract

SYNOPSIS Whereas in current practice in the United States, select is that form of precipitation which is not snow, rain, or hail, an attempt to make a detailed descriptive and genetic definition seems advisable, and 30 cases of sleet are analyzed as a basis: Select, a rattling type of ice precipitation formed in the free air, has the following characteristics: Size, smallest dimensions of largest pieces less than 6 mm. (¼ inch); form, angular, irregular, or nearly spherical; structure, nonregular ice part or all of which is cloudy or bubbly (except in extremely small drops), not more than one clear layer. A select particle may be (1) a snowflake partly melted and refrozen. (2) a frozen raindrop, or (3) a frozen combination of snowflake, and raindrop or liquid (not undercooled) cloud droplets. A generalized vertical section of sleet weather shows select as occurring usually with a cloud from which snow is falling through a stratum of air having a temperature above freezing and into air with a temperature below freezing.