- Industry: Weather
- Number of terms: 60695
- Number of blossaries: 0
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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 cyclone in tropical or subtropical latitudes (from the equator to about 50°N) that has characteristics of both tropical cyclones and midlatitude (or extratropical) cyclones. They occur in regions of weak to moderate horizontal temperature gradient and extract the associated available potential energy, as do baroclinic cyclones, but they also receive some or most of their energy from convective redistribution of heat acquired from the sea, as do tropical cyclones. These storms usually have a radius of maximum winds that is larger than what is observed in purely tropical systems, and their maximum sustained winds have not been observed to exceed about 32 m s<sup>−1</sup> (64 knots). Subtropical cyclones sometimes become true tropical cyclones, and likewise, tropical cyclones occasionally become subtropical storms. Subtropical cyclones in the Atlantic basin are classified by their maximum sustained surface winds: Subtropical depressions have surface winds less than 18 m s<sup>−1</sup> (35 knots), while subtropical storms have surface winds greater than or equal to 18 m s<sup>−1</sup>. While these storms are not given names, forecasters do issue warnings for them.
Industry:Weather
A cumulus cloud that is no longer dynamically connected with the atmospheric boundary layer via updrafts or downdrafts. These clouds decay and dissipate just above the boundary layer top and can leave behind a concentration of pollutants. The clouds are radiatively coupled with the boundary layer and shade the ground.
Industry:Weather
A current below a surface current, therefore not in direct contact with the atmosphere.
Industry:Weather
A current in which an approximate geostrophic balance between Coriolis and pressure gradient forces holds, but for which other terms, generally the inertial terms involving temporal change or advective acceleration, play a key dynamic role (through vortex stretching effects) despite their relatively small magnitude. For the geostrophic approximation to hold, the flow must be nearly steady (timescale >> pendulum day), weak, and large-scale (small Rossby number), with negligible friction (small Ekman number).
Industry:Weather
A crisp, firm, outer surface upon snow. Basically, three types of snow crusts exist, formed by 1) the refreezing of surface snow, after melting and/or wetting, to form a hard layer of snow (sun crust, rain crust, spring crust); 2) the packing of snow into a hard layer by wind action (wind crust, wind slab); and 3) the freezing of surface water, however derived, to form a continuous layer of ice on top of snow (film crust, ice crust). A snow crust is designated as “breakable” or “unbreakable” according to its ability to support a person on skis.
Industry:Weather
A cumulus cloud formed by a rising thermal from a fire, or enhanced by buoyant plume emissions from an industrial combustion process. See'' also'' venting mixed layer air.
Industry:Weather
A coordinate system in which atmospheric pressure is taken as the vertical coordinate. Compare θ coordinate system.
Industry:Weather
A core of strong westerly winds that develop during autumn and winter in the upper stratosphere and mesosphere near the boundary of the polar night. Radiative cooling in the polar night appears to maintain the required baroclinicity.
Industry:Weather
