Subj : Wx Terms (A)(1) To : All From : Daryl Stout Date : Thu Nov 02 2017 12:06 am A 1. Abbrevation for hail in weather observations. 2. Symbol used on long-term climate outlooks issued by CPC to indicate areas that are likely to be above normal for the specified parameter (temperature, precipitation, etc.). A AMS Arctic Air Mass A Index A daily index of geomagnetic activity derived as the average of the eight 3-hourly a indices. AAAS American Association for the Advancement of Science AAWU Alaskan Aviation Weather Unit Ablation Depletion of snow and ice by melting and evaporation. ABNDT Abundant Absolutely Stable Air An atmospheric condition that exists when the environmental lapse rate is less than the moist adiabatic lapse rate. Absolutely Unstable Air An atmospheric condition that exists when the environmental lapse rate is greater than the dry adiabatic lapse rate. Absorption The process in which incident radiant energy is retained by a substance by conversion to some other form of energy. ABT About Abutment The part of a valley or canyon wall against which a dam is constructed. Right and left abutments are those on respective sides of an observer looking downstream. Abutment Seeping Reservoir water that moves through seams or pores in the natural abutment material and exits as seepage. ABV Above AC 1. Abbreviation for 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). 2. Convective outlook issued by the Storm Prediction Center. Abbreviation for Anticipated Convection; the term originates from the header coding [ACUS1] of the transmitted product. ACCAS (usually pronounced ACK-kis) - AltoCumulus CAStellanus; mid-level clouds (bases generally 8 to 15 thousand feet), of which at least a fraction of their upper parts show cumulus-type development. These clouds often are taller than they are wide, giving them a turret-shaped appearance. ACCAS clouds are a sign of instability aloft, and may precede the rapid development of thunderstorms. Accessory Cloud A cloud which is dependent on a larger cloud system for development and continuance. Roll clouds, shelf clouds, and wall clouds are examples of accessory clouds. Accretion The growth of a precipitation particle by the collision of a frozen particle with a supercooled liquid water droplet which freezes upon impact. ACCUMS accumulation Accuracy Degree of conformity of a measure to a standard or true value; in other words, how close a predicted or measured value is to the true value. Acid Precipitation Precipitation, such as rain, snow or sleet, containing relatively high concentrations of acid-forming chemicals that have been released into the atmosphere and combined with water vapor; harmful to the environment. Acid Rain Rain containing relatively high concentrations of acid-forming chemicals that have been released into the atmosphere and combined with water vapor; harmful to the environment. ACLD Above Cloud Level ACPY Accompany Acre-foot The amount of water required to cover one acre to a depth of one foot. An acre-foot equals 326,851 gallons, or 43,560 cubic feet. ACRS Across Action Stage The stage which, when reached by a rising stream, represents the level where the NWS or a partner/user needs to take some type of mitigation action in preparation for possible significant hydrologic activity. The appropriate action is usually defined in a weather forecast office (WFO) hydrologic services manual. Action stage can be the same as forecast issuance stage. Active (abbrev. ACTV). In solar-terrestrial terms, solar activity levels with at least one geophysical event or several larger radio events (10cm) per day (Class M Flares). Active Conservation Storage In hydrologic terms, the portion of water stored in a reservoir that can be released for all useful purposes such as municipal water supply, power, irrigation, recreation, fish, wildlife, etc. Conservation storage is the volume of water stored between the inactive pool elevation and flood control stage. Active Dark Filament (ADF) In solar-terrestrial terms, an Active Prominence seen on the Disk. Active Longitude In solar-terrestrial terms, the approximate center of a range of heliographic longitudes in which Active Regions are more numerous and more flare-active than the average. Active Prominence In solar-terrestrial terms, a prominence displaying material motion and changes in appearance over a few minutes of time. Active Prominence Region (APR) In solar-terrestrial terms, a portion of the solar limb displaying active prominences. Active Region (AR) In solar-terrestrial terms, a localized, transient volume of the solar atmosphere in which plages, sunspots, faculae, flares, etc. may be observed. Active Storage Capacity In hydrologic terms, the total amount of reservoir capacity normally available for release from a reservoir below the maximum storage level. It is total or reservoir capacity minus inactive storage capacity. More specifically, it is the volume of water between the outlet works and the spillway crest. Active Surge Region (ASR) In solar-terrestrial terms, an Active Region that exhibits a group or series of spike-like surges that rise above the limb. ACTV Active. In solar-terrestrial terms, solar activity levels with at least one geophysical event or several larger radio events (10cm) per day (Class M Flares) ACYC Anticyclone - A large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere. Additive Data A group of coded remarks that includes pressure tendency, amount of precipitation, and maximum/minimum temperature during specified periods of time. ADDS Aviation Digital Data Service Adiabat A line on a thermodynamic chart relating the pressure and temperature of a substance (such as air) that is undergoing a transformation in which no heat is exchanged with its environment. --- þ Synchronet þ The Thunderbolt BBS - wx1der.dyndns.org .