Subj : Wx Terms (A)(3) To : All From : Daryl Stout Date : Sun Jul 02 2017 12:04 am Air Toxin Toxic air pollutant. Air Transportable Mobile Unit A modularized transportable unit containing communications and observational equipment necessary to support a meteorologist preparing on-site forecasts at a wildfire or other incident. Airborne Snow Survey Program In hydrologic terms, Center (NOHRSC) program that makes airborne snow water equivalent and soil moisture measurements over large areas of the country that are subject to severe and chronic snowmelt flooding. AIRMET Airman's Meteorological advisory (WA) AIV Aviation Impact Variables Alaska Current A North Pacific Ocean current flowing counterclockwise in the Gulf of Alaska. It is the northward flowing (warm) division of the Aleutian Current. Albedo Reflectivity; the fraction of radiation striking a surface that is reflected by that surface. Alberta Clipper A fast moving low pressure system that moves southeast out of Canadian Province of Alberta (southwest Canada) through the Plains, Midwest, and Great Lakes region usually during the winter. This low pressure area is usually accompanied by light snow, strong winds, and colder temperatures. Another variation of the same system is called a "Saskatchewan Screamer". ALERT Automated Local Event Reporting in Real Time. Network of automatic raingauges that transmit via VHF radio link when precipitation occurs. Some sites are also equipped with other sensors such as temperature, wind, pressure, river stage or tide level. Alert Stage The stage which, when reached by a rising stream, represents the level where appropriate officials (e.g., county sheriff, civil defense officials, or bypass gate operators) are notified of the threat of possible flooding. (Used if different from action stage, and at the discretion of the WFO or river forecast center [RFC].) The term "alert stage" is to be used instead of warning stage. Monitor stage or caution stage may be used instead of alert stage in some parts of the country. Aleutian Current An eastward flowing North Pacific Ocean current which lies north of the North Pacific Current. Aleutian Low A semi-permanent, subpolar area of low pressure located in the Gulf of Alaska near the Aleutian Islands. It is a generating area for storms and migratory lows often reach maximum instensity in this area. It is most active during the late fall to late spring. During the summer, it is weaker, retreating towards the North Pole and becoming almost nonexistent. During this time, the North Pacific High pressure system dominates. ALF Aloft ALG Along Algorithm A computer program (or set of programs) which is designed to systematically solve a certain kind of problem. WSR-88D radars (NEXRAD) employ algorithms to analyze radar data and automatically determine storm motion, probability of hail, VIL, accumulated rainfall, and several other parameters. Alluvium Sediments deposited by erosional processes, usually by streams. Along-slope Wind System A closed, thermally driven diurnal mountain wind circulation whose lower branch blows up or down the sloping sidewalls of a valley or mountain. The upper branch blows in the opposite direction, thereby closing the circulation. ALQDS All Quadrants ALTHO although Altimeter An instrument that indicates the altitude of an object above a fixed level. Pressure altimeters use an aneroid barometer with a scale graduated in altitude instead of pressure. Altimeter Setting A correction of the station pressure to sea level used by aviation. This correction takes into account the standard variation of pressure with height and the influence of temperature variation with height on the pressure. The temperatures used correspond to the standard atmosphere temperatures between the surface and sea level. Altocumulus A cloud of a class characterized by globular masses or rolls in layers or patches, the individual elements being larger and darker than those of cirrocumulus and smaller than those of stratocumulus. These clouds are of medium altitude, about 8000-20,000 ft (2400-6100 m). Altostratus A cloud of a class characterized by a generally uniform gray sheet or layer, lighter in color than nimbostratus and darker than cirrostratus. These clouds are of medium altitude, about 8000 to 20,000 ft (2400-6100 m). Ambient Of the surrounding area or environment. AMD Amend AMOS Automatic Meteorological Observing System Amplifier A device used to increase the strength of an analog signal Amplitude The maximum magnitude of a quantity. Often used to refer to the maximum height of a wave. AMS 1. Air Mass - a body of air covering a relatively wide area and exhibiting horizontally uniform properties. 2. American Meteorological Society AMT Amount AMVER Automated Mutual Assistance Vessel Rescue System. A system operated by the U.S. Coast Guard which computes the nearest available rescue vessels for vessels in distress using vessel track and position reports supplied by participating vessels. AMVER/SEAS A software program created by the National Weather Service intended to efficiently generate AMVER and VOS reports as part of a cooperative effort. Anabranch A diverging branch of a river which re-enters the main stream. Analog 1. Class of measuring devices in which the output varies continuously as a function of the input (non-digital). 2. A historical instance of a given meteorological scenario or feature that is used for comparison with another scenario or feature. For example, a long-range forecaster predicting conditions for the upcoming winter may make comparisons to analog seasons in which meteorological factors were similar to those of the upcoming season. Analog Signal A signal, such as voice, that varies in a continuous manner. ANBURS Alphanumeric Backup Replacement System Anchor Ice In hydrologic terms, submerged frazil ice attached or anchored to the river bottom, irrespective of its formation. Anchor Ice Dam An accumulation of anchor ice which acts as a dam and raises the water level. Anemometer An instrument used for measuring the speed of the wind. Aneroid Barometer An instrument for measuring atmospheric pressure in which a needle, attached to the top of an evacuated box, is deflected as changes in atmospheric pressure cause the top of the box to bend in or out. Angels Radar echoes caused by birds, insects, and localized refractive index discontinuities. --- þ Synchronet þ The Thunderbolt BBS - wx1der.dyndns.org .