Subj : Wx Terms (A)(5) To : All From : Daryl Stout Date : Mon Oct 02 2017 12:04 am Arctic Sea Smoke Steam fog, but often specifically applied to steam fog rising from small open water within sea ice. Arcus A low, horizontal cloud formation associated with the leading edge of thunderstorm outflow (i.e., the gust front). Roll clouds and shelf clouds both are types of arcus clouds. Area Forecast Discussion This National Weather Service product is intended to provide a well-reasoned discussion of the meteorological thinking which went into the preparation of the Zone Forecast Product. The forecaster will try to focus on the most particular challenges of the forecast. The text will be written in plain language or in proper contractions. At the end of the discussion, there will be a list of all advisories, non-convective watches, and non-convective warnings. The term non-convective refers to weather that is not caused by thunderstorms. An intermediate Area Forecast Discussion will be issued when either significant forecast updates are being made or if interesting weather is expected to occur. Area of Influence In hydrologic terms, the area covered by the drawdown curves of a given pumping well or combination of wells at a particular time. Area Source An array of pollutant sources, so widely dispersed and uniform in strength that they can be treated in a dispersion model as an aggregate pollutant release from a defined area at a uniform rate. Compare line source and point source. Area Wide Hydrologic Prediction System (Abbrev. AWHPS) - A computer system which automatically ingests areal flash flood guidance values and WSR-88D products and displays this data and other hydrologic information on a map background. Area-Capacity Curve In hydrologic terms, a graph showing the relation between the surface area of the water in a reservoir, the corresponding volume, and elevation. Arid An adjunctive applied to regions where precipitation is so deficient in quantity, or occurs at such times, that agriculture is impracticable without irrigation. ARINC Aeronautical Radio, Incorporated ARND Around ARR Arrive/Arrival Arroyo In hydrologic terms, a water-carved channel or gully in arid country, usually rather small with steep banks, dry most of the time, due to infrequent rainfall and the shallowness of the cut which does not penetrate below the level of permanent ground water. ARSI Atmospheric Research System, Inc. ART The Automatic Radiotheodolite. A ground-based radio direction finder that automatically tracks a ballon-borne radiosonde. ARTCC Air Route Traffic Control Center Artesian Well In hydrologic terms, a well drilled into a confined aquifer with enough hydraulic pressure for the water to flow to the surface without pumping. Also called a flowing well. Artificial Control In hydrologic terms, a weir or other man-made structure which serves as the control for a stream-gaging station. AS (NOTE: if this appears in an Area Forecast Discussion or other text product in context as the word "as," disregard the technical definition below). Abbreviation for 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). ASAP 1. AHOS SHEF Automatic Processing System 2. As soon as possible (may be used in Area Forecast Discussions) ASAPTRAN The software component of ASAP. ASB Aviation Support Branch ASL Above Sea Level ASOS Automated Surface Observing System Astronomical Dawn The time at which the sun is 18ø below the horizon in the morning. Astronomical dawn is that point in time at which the sun starts l ightening the sky. Prior to this time during the morning, the sky is completely dark. Astronomical Dusk This is the time at which the sun is 18ø below the horizon in the evening. At this time the sun no longer illuminates the sky. Astronomical Unit (abbrev. AU)- The mean earth-sun distance, equal to 1.496x1013 cm, or 214.94 solar radii. ATC Air Traffic Control ATDTDCS Automated Tone Dial Telephone Data Collection System - Data collection system where cooperative observers collect precipitation, stage, and temperature data then transmit the data to the NWS ATDTDCS computer through the telephone lines. The ATDTDCS computer transmits the data to AFOS. Atmosphere The air surrounding and bound to the Earth. Atmospheric Boundary Layer Same as Boundary Layer - in general, a layer of air adjacent to a bounding surface. Specifically, the term most often refers to the planetary boundary layer, which is the layer within which the effects of friction are significant. For the earth, this layer is considered to be roughly the lowest one or two kilometers of the atmosphere. It is within this layer that temperatures are most strongly affected by daytime insolation and nighttime radiational cooling, and winds are affected by friction with the earth's surface. The effects of friction die out gradually with height, so the "top" of this layer cannot be defined exactly. Atmospheric Circulation Model A mathematical model for quantitatively describing, simulating, and analyzing the structure of the circulation in the atmosphere and the underlying causes. Sometimes referred to as Atmospheric General Circulation Models or AGCMs. Atmospheric Pressure The pressure exerted by the earth's atmosphere at any given point, determined by taking the product of the gravitational acceleration at the point and the mass of the unit area column of air above the point. Atmospheric Radiation Infrared radiation (energy in the wavelength interval of 3 -80 micrometer) emitted by or being propagated through the atmosphere. It consists of both upwelling and downwelling components. Compare with terrestrial radiation. ATMP On a buoy report, the air temperature (Celsius). Attenuation It refers to the reduction of the radar beam power due to the reflection or absorption of energy when it strikes a target. The greatest attenuation occurs when the radar beam goes through very heavy rain. ATTM At this time Augmented report A meteorological report prepared by an automated surface weather observing system for transmission with certified observers signed on to the system to add information to the report. Aurora A faint visual phenomenon associated with geomagnetic activity, which occurs mainly in the high-latitude night sky; typical auroras are 100 to 250 km above the ground. Aurora Australis Same as Aurora Borealis, but in the Southern Hemisphere. Also known as the southern lights; the luminous, radiant emission from the upper atmosphere over middle and high latitudes, and centred around the earth's magnetic poles. These silent fireworks are often seen on clear winter nights in a variety of shapes and colors. Aurora Borealis Also known as the northern lights; the luminous, radiant emission from the upper atmosphere over middle and high latitudes, and centred around the earth's magnetic poles. These silent fireworks are often seen on clear winter nights in a variety of shapes and colors. --- þ Synchronet þ The Thunderbolt BBS - wx1der.dyndns.org .