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Show New Ideas Expected to Aid Weather Prophets slope of air wedges, and rapidity of warm air ascent. Along the "cold front" the advancing advanc-ing polar, or cold, air forms a wedge or thrust under the warm air, and the precipitation is squally, usually, however, covering only a comparatively compara-tively 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 a!r masses, when the drama is re-enacted. Air mass analysis, methods for 'which have been developed largely during the last decade, is rapidly as-j as-j Burning an Important place in forecasting fore-casting the weather. Greater detail I In observational material than Is or-idlnarily or-idlnarily available Is necessary for ; such forecasting. The air-mass analysis method of forecasting calls for the study of two or more conflicting masses of air, usually of widely different origin, and consequently of different characteristics char-acteristics as to temperature and moisture, which come together along what is called a line of discontinuity, discontinu-ity, a polar front, or a wind shift. Air over polar regions, of course, Is much colder than that over tropical trop-ical regions. The transition, however, Is neither gradual nor regular. Instead, In-stead, large masses of air in one or the other region become supercooled or superheated. These masses develop devel-op into "surges," or "bulges," that meet along an irregular line. Because Be-cause they differ structurally in temperature tem-perature and moisture, and therefore density, the masses do not mix In an orderly fashion but tend to preserve their own Identities. This results in a battle for supremacy, which forms the ever-changing drama that Is our weather. The air from the polar regions Is cold, dry, heavy, and relatively cloudless. cloud-less. That from the tropical regions Is warm, moist, relatively light, and cloudy. At the line where they meet, the advancing tropical air, being warm, moist, and therefore lighter, Is forced to ascend and flow northward north-ward over the wedge of cold air at the surface. This Is called the "warm front." The air as It rises Is cooled by expansion, and the moisture In it Is condensed into clouds from which rain or snow may fall. The amount and duration of this precipitation depend on several factors, including wind direction, amount of moisture, |