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. Accretion The growth of a precipitation particle by the collision of a frozen particle with a supercooled liquid water droplet which freezes upon impact. Roll clouds, shelf clouds, and wall clouds are examples of accessory clouds. Accessory Cloud A cloud which is dependent on a larger cloud system for development and continuance. Absorption The process in which incident radiant energy is retained by a substance by conversion to some other form of energy. Absolutely Stable Air An atmospheric condition that exists when the environmental lapse rate is less than the moist adiabatic lapse rate.Ībsolutely Unstable Air An atmospheric condition that exists when the environmental lapse rate is greater than the dry adiabatic lapse rate. 100-year Flood Plain The flood plain that would be inundated in the event of a 100-year flood. The 100-year flood is usually developed from a statistical distribution that is based on historical floods. 100-year Flood A statistic that indicates the magnitude of flood which can be expected to occur on average with a frequency of once every 100 years at a given The wind radii may be found within Tropical Cyclone Forecast Advisory (TCM) forecasts. The forecast track error is added to the 34 knot wind radii to compute the danger area. NOAA's National Weather Service - Glossary 1-2-3 Rule A means of avoiding winds associated with a tropical cyclone by taking into account the forecast track error of the National Weather Service over a 10 year period which is approximately 100 nm in 24 hours, 200 nm for 48 hours and 300 nm in 72 hours.