Show CONTRASTING THUNDERSTORMS IS Some thunderstorms are arc wind hatch hatched d others are calm brooded Humidity of the air decrease dur dur- during during during ing storms storms of the first type and increases durin during those of the sec sec- second second sec second ond type according to a recent study by Dr R W J Humphreys of the United States Weather bureau au Wind-hatched Wind storms also known as cold front and squall line thunderstorms are caused by bv cool cool- cooling coolin cooling in ing from above e usually the result of the importation of cold eold air Wind is necessary for the creation of such storms Calm-brooded Calm or heat thunder thunder- thunderstorms thunderstorms thunder storms storms are arc caused by warming be- be below below be below low from exposure to the sun These storms grow ow from small to tolar large lar e circular flows of warm air strai straight ht up from the earths earth's sur sur- surface surface surface face These chimney like storms arise only when there is no win wind As the absolute humidity of theair the theair theair air on all sides of a heat thunder thunder- thunderstorm thunder thunder- thunder storm is about the same the oration oration of the fallin falling rain increases es the density of the atmospheric vapor making the humidity great great- greater greater reat er than it was before the storm The distribution of the absolute humidity about the front cold cold storm however is unequal It is much greater eater in the warm air in front of the storm than it is in the cold air to the rear The absolute humidity therefore decreases s as the storm passes over |