| Show new ideas kar expected erected V to aid weather prophets prophet S air mass analysis methods for which have been developed largely during the last decade Is rapidly assuming an important place in forecasting tile the weather greater detail in observational material than Is ordinarily din dina rily arlly R available val lable Is necessary for such buch forecasting the air mass rina analysis lysis method ol of forecasting calls for the lie study of 0 two or more conflicting masses of air usually of widely different origin and consequently of different characteristics acte as to temperature and moisture which come together along what Is called a line of 0 discontini discon discontinuity tinn a polar front or a wind shift air over polar regions of 0 course Is much colder than that over tropical regions the transition however Is neither gradual nor regular instead large masses of air in one or the other region become super cooled or superheated super heated these masses develop into surges or bulges that meet along an irregular line because they differ structurally in temperature pera ture and moisture and therefore density the masses do not mix mis in an orderly fashion but tend to preserve their own identities this results in a battle for supremacy holcli forms the ever changing drama that Is our weather the air from the polar regions Is cold dry heavy and relatively cloudless that from the tropical regions Is warm moist relatively light and cloudy at tile the line where they meet the advancing tropical air being warm moist and therefore lighter Is forced to ascend and flow northward over the wedge of cold air nt at the surface this Is called the warm front the air as it rises Is cooled by expansion and the moisture in it la Is condensed into clouds from which rain or snow nay may fall the amount and duration of this precipitation depend on several factors including wind direction amount of moisture slope of air wedges and rapidity of warm air ascent along the cold front the advancing polar or cold air forms a wedge or thrust under the warm air and the precipitation Is squally usually however covering only a comparatively small area accompanying these precipitations are marked and sudden changes in temperature and wind followed by a more or less steady state until the next meeting of conflicting air masses when the drama Is reen re en acted |
