Subj : Wx Terms (F)(4) To : All From : Daryl Stout Date : Sat Oct 07 2017 12:04 am Fountainhead In hydrologic terms, the upper end of a confined-aquifer conduit, where it intersects the land surface. FOUS Forecast Output United States FPO Flood Potential Outlook FPS Fujita-Pearson Scale FQT Frequent Fractocumulus A cumulus cloud presenting a ragged, shredded appearance, as if torn. Fractostratus A stratus cloud presenting a ragged, shredded appearance, as if torn. It differs from a fractocumulus cloud in having a smaller vertical extent and darker color. Fracture In hydrologic terms, any break or rupture formed in an ice cover or floe due to deformation. Fracture Zone In hydrologic terms, an area which has a great number of fractures. Fracturing In hydrologic terms, deformation process whereby ice is permanently deformed, and fracture occurs. Fractus Ragged, detached cloud fragments; same as scud. Frazil Ice In hydrologic terms, fine spicules, plates, or discoids of ice suspended in water. In rivers and lakes, frazil is formed in supercooled, turbulent water. Frazil Slush In hydrologic terms, an agglomerate of loosely packed frazil which floats or accumulates under the ice cover. Freak Wave A wave of much greater height and steepness than other waves in the prevailing sea or swell system. See Rogue Wave. Free Atmosphere The part of the atmosphere that lies above the frictional influence of the earth's surface. Free Ground Water In hydrologic terms, unconfined ground water whose upper boundary is a free water table. Freeboard In hydrologic terms, the vertical distance between the normal maximum level of the water surface in a channel, resrvoir, tank, canal, etc., and the top of the sides of a levee, dam, etc., which is provided so that waves and other movements of the liquid will not overtop the confining structure. Freeze A freeze is when the surface air temperature is expected to be 32øF or below over a widespread area for a climatologically significant period of time. Use of the term is usually restricted to advective situations or to occasions when wind or other conditions prevent frost. "Killing" may be used during the growing season when the temperature is expected to be low enough for a sufficient duration to kill all but the hardiest herbaceous crops. Freeze Warning Issued during the growing season when surface temperatures are expected to drop below freezing over a large area for an extended period of time, regardless whether or not frost develops. Freezeup date In hydrologic terms, the date on which the water body was first observed to be completely frozen over. Freezing Drizzle A drizzle that falls as a liquid but freezes into glaze or rime upon contact with the cold ground or surface structures. Freezing Drizzle Advisory Issued when freezing rain or freezing drizzle is forecast but a significant accumulation is not expected. However, even small amounts of freezing rain or freezing drizzle may cause significant travel problems. Freezing Fog A suspension of numerous minute ice crystals in the air, or water droplets at temperatures below 0ø Celsius, based at the Earth's surface, which reduces horizontal visibility; also called ice fog. Freezing Level The altitude at which the air temperature first drops below freezing. Freezing Rain Rain that falls as a liquid but freezes into glaze upon contact with the ground. Freezing Rain Advisory Issued when freezing rain or freezing drizzle is forecast but a significant accumulation is not expected. However, even small amounts of freezing rain or freezing drizzle may cause significant travel problems. Freezing Spray An accumulation of freezing water droplets on a vessel caused by some appropriate combination of cold water, wind, cold air temperature, and vessel movement. Freezing Spray Advisory An advisory that may be issued within the Offshore Waters Forecast, the Coastal Waters Forecast, the Nearshore Marine Forecast, and the Open Lake Forecast (GLF). An accumulation of freezing water droplets on a vessel at a rate of less than 2 centimeters (cm) per hour caused by some appropriate combination of cold water, wind, cold air temperature, and vessel movement. Freezup jam In hydrologic terms, ice jam formed as frazil ice accumulates and thickens. French Drain In hydrologic terms, an underground passageway for water through the interstices among stones placed loosely in a trench. Freshet The annual spring rise of streams in cold climates as a result of snow melt; freshet also refers to a flood caused by rain or melting snow. Friction The mechanical resistive force of one object on another object's relative movement when in contact with the first object. In meteorology, friction affects the motion of air (wind) at and near the Earth's surface. Friction Head In hydrologic terms, the decrease in total head caused by friction. Friction Layer Same as Planetary Boundary Layer; the layer within the atmosphere between the earth's surface and 1 km above the surface; this is the layer where friction affects wind speed and wind direction. FRMG Forming Front A boundary or transition zone between two air masses of different density, and thus (usually) of different temperature. A moving front is named according to the advancing air mass, e.g., cold front if colder air is advancing. Frontal Inversion A temperature inversion that develops aloft when warm air overruns the cold air behind a front. Frontogenesis 1. The initial formation of a front or frontal zone. 2. In general, an increase in the horizontal gradient of an airmass property, principally density, and the development of the accompanying features of the wind field that typify a front. FROPA Frontal Passage FROSFC Frontal Surface Frost (Abbrev. FRST) - Frost describes the formation of thin ice crystals on the ground or other surfaces in the form of scales, needles, feathers, or fans. Frost develops under conditions similar to dew, except the temperatures of the Earth's surface and earthbound objects falls below 32øF. As with the term "freeze," this condition is primarily significant during the growing season. If a frost period is sufficiently severe to end the growing season or delay its beginning, it is commonly referred to as a "killing frost." Because frost is primarily an event that occurs as the result of radiational cooling, it frequently occurs with a thermometer level temperature in the mid-30s. Frost Advisory Issued during the growing season when widespread frost formation is expected over an extensive area. Surface temperatures are usually in the mid 30s Fahrenheit. Frost Point Dew point below freezing. --- þ Synchronet þ The Thunderbolt BBS - wx1der.dyndns.org .