- Industry: Weather
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The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, AMS has a membership of more than 14,000 professionals, ...
A form of convection driven by a combination of gravitational and centrifugal forces. Slantwise convection can occur in baroclinic flows in which the slantwise-upward displacement of air parcels, elongated in the direction of the thermal wind, results in a vector combination of buoyancy and Coriolis (or centrifugal) and pressure-gradient accelerations that drive the parcel in the same direction as the displacement. See'' also'' symmetric instability.
Industry:Weather
A form of cloud seeding in which salt particles are released into the atmosphere with the objective of increasing precipitation. The salt particles are hygroscopic and readily condense water and grow large enough to become centers for coalescence growth of precipitation, or participate in the ice accretion process. See cloud seeding, weather modification.
Industry:Weather
A form of double-diffusive convection that occurs when warm, salty water overlies cold freshwater. A parcel of freshwater moved upward will gain heat more quickly than it gains salt and so will become lighter than the surrounding water. It will rise unstably as a result. Salt fingering has been observed in the Caribbean Sea where it gives rise to stable layers hundreds of kilometers in extent. The process transports salt much more efficiently than heat. See'' also'' Turner angle.
Industry:Weather
A form of cloud discharge, generally horizontal and at cloud base, with a luminous channel appearing to advance through the air with visually resolvable speed, often intermittently.
Industry:Weather
A form of artificial lightning discharge initiated with a rocket trailing wire that may or may not be connected to the ground. The first phase of the discharge is a unidirectional leader starting from the tip of the wire. When the low end of the wire is not connected to ground, bidirectional leader development occurs from both ends of the wire, similar to lightning initiation from aircraft. In the case of negative space charge overhead (usual summer thunderstorm condition), a triggered lightning may only be a positive leader or may become a sequence of dart leader–return stroke processes following the initial positive leader. The latter is analogous to the subsequent return stroke process in a negative cloud-to-ground flash with the initial positive leader being analogous to the first return stroke. In the case of positive space charge overhead (usual winter storm condition), the triggered lightning is a single negative leader.
Industry:Weather
A forecast of the expected stage or discharge at a specified time, or of the total volume of flow within a specified time interval, at one or more points along a stream.
Industry:Weather
A forecast of the probability of occurrence of one or more categorical events. Compare persistence forecast, random forecast.
Industry:Weather
A forecast based on decisions made by an individual. Conversely, an objective forecast is based solely on the results from a set of mathematical equations or numerical model.
Industry:Weather
A forecast based on a systematic statistical examination of data representing past observed behavior of the system to be forecast, including observations of useful predictors outside the system. In short-term climate forecasting, CCA (canonical correlation analysis), as described by Barnston (1994), is a good example of a statistical forecast. Depending on method and scope, the limitations of statistical forecasts are related to shortness of record, danger of overfitting, assumptions of linearity (often), absence (often) of physical considerations, etc. Purely statistical forecasts in weather forecasting have become rare; however, a combination of dynamical model output and statistics is very common in weather forecasting. Some statistical methods are guided by physical principles to such an extent that they resemble dynamical models. An example of the latter is empirical wave propagation described by Qin and van den Dool (1996). See perfect prognosis method, MOS.
Industry:Weather
A foehn wind blowing from south (northern Italy) to north (Switzerland, southern Germany, and western Austria) over the Alps. Because these winds blow from a warmer region to a cooler region, they are often accompanied by dramatic temperature and wind speed increases. The south foehn often results from flow in the warm sector of a cyclone system and thus it often occurs ahead of a cold front.
Industry:Weather
