Subj : Wx Terms (L)(2) To : All From : Daryl Stout Date : Tue Jun 13 2017 12:05 am Lee The side or part that is sheltered or turned away from the wind, such as with a mountain. Lee Wave The wavelike effect, characterized by severe updrafts and downdrafts, that occurs in the lee of a mountain range when rapidly flowing air is lifted up the steep front of a mountain range. Compare mountain wave. Leeside Low Extratropical cyclones that form on the downwind (lee) side of a mountain chain. In the United States, they frequently form on the eastern side of the Rockies and Sierra Nevadas. Leeward The side away from the wind. Compare windward. Left Exit Region Used interchangably with Left Front Quadrant; the area downstream from and to the left of an upper-level jet max (as would be viewed looking along the direction of flow). Upward motion and severe thunderstorm potential sometimes are increased in this area relative to the wind speed maximum. See also entrance region, right rear quadrant. Left Front Quadrant Used interchangably with Left Exit Region; the area downstream from and to the left of an upper-level jet max (as would be viewed looking along the direction of flow). Upward motion and severe thunderstorm potential sometimes are increased in this area relative to the wind speed maximum. See also entrance region, right rear quadrant. Left Mover A thunderstorm which moves to the left relative to the steering winds, and to other nearby thunderstorms; often the northern part of a splitting storm. Length In hydrologic terms, the distance in the direction of flow between two specific points along a river, stream, or channel. Lentic System In hydrologic terms, a nonflowing or standing body of fresh water, such as a lake or pond. Lenticular Cloud A very smooth, round or oval, lens-shaped cloud that is often seen, singly or stacked in groups, near or in the lee of a mountain ridge. Levee (Dike) In hydrologic terms, a long, narrow embankment usually built to protect land from flooding. If built of concrete or masonary the structure is usually referred to as a flood wall. Levees and floodwalls confine streamflow within a specified area to prevent flooding. The term "dike" is used to describe an embankment that blocks an area on a reservoir or lake rim that is lower than the top of the dam. Level of Free Convection (LFC) - The level at which a parcel of saturated air becomes warmer than the surrounding air and begins to rise freely. This occurs most readily in a conditionally unstable atmosphere. LEWP Line Echo Wave Pattern. A bulge in a thunderstorm line producing a wave-shaped "kink" in the line. The potential for strong outflow and damaging straight-line winds increases near the bulge, which often resembles a bow echo. Severe weather potential also is increased with storms near the crest of a LEWP. LFC An acronym for Level of Free Convection- the level at which a parcel of saturated air becomes warmer than the surrounding air and begins to rise freely. This occurs most readily in a conditionally unstable atmosphere. LFT Lift LGT Light LGWV Long Wave LI Lifted Index. A common measure of atmospheric instability. Its value is obtained by computing the temperature that air near the ground would have if it were lifted to some higher level (around 18,000 feet, usually) and comparing that temperature to the actual temperature at that level. Negative values indicate instability - the more negative, the more unstable the air is, and the stronger the updrafts are likely to be with any developing thunderstorms. However there are no "magic numbers" or threshold LI values below which severe weather becomes imminent. Lid (Also called cap.) A region of negative buoyancy below an existing level of free convection (LFC) where energy must be supplied to the parcel to maintain its ascent. This tends to inhibit the development of convection until some physical mechanism can lift a parcel to its LFC. The intensity of the cap is measured by its convective inhibition. The term capping inversion is sometimes used, but an inversion is not necessary for the conditions producing convective inhibition to exist. LIFR Low Instrument Flight Rules Lifted Index (abbrev. LI)- A common measure of atmospheric instability. Its value is obtained by computing the temperature that air near the ground would have if it were lifted to some higher level (around 18,000 feet, usually) and comparing that temperature to the actual temperature at that level. Negative values indicate instability - the more negative, the more unstable the air is, and the stronger the updrafts are likely to be with any developing thunderstorms. However there are no "magic numbers" or threshold LI values below which severe weather becomes imminent. Lifting Condensation Level (LCL) - The level at which a parcel of moist air becomes saturated when it is lifted dry adiabatically. Light Bridge In solar-terrestrial terms, it is observed in white light, a bright tongue or streaks penetrating or crossing sunspot umbrae. The appearance of a light bridge is frequently a sign of impending region division or dissolution. Lightning (abbrev. LTNG) A visible electrical discharge produced by a thunderstorm. The discharge may occur within or between clouds, between the cloud and air, between a cloud and the ground or between the ground and a cloud. Lightning Channel The irregular path through the air along which a lightning discharge occurs. A typical discharge of flash between the ground and the cloud is actually a composite flash which is composed of several sequential lightning strokes, each of which is initiated by a leader and terminated by a return streamer. Lightning Discharge The series of electrical processes by which charge is transferred along a channel of high ion density between electrical charge centers of opposite sign. This can be between a cloud and the Earth's surface of a cloud-to-ground discharge. Lightning Stroke Any of a series of repeated electrical discharges comprising a single lightning discharge (strike). Specifically, in the case of a cloud-to-ground discharge, a leader plus its subsequent return streamer. Likely (abbrev. LKLY) In probability of precipitation statements, the equivalent of a 60 or 70 percent chance. Limb In solar-terrestrial terms, the edge of the solar disk. Limb Flare In solar-terrestrial terms, a solar flare seen at the edge (Limb) of the sun. Limnology In hydrologic terms, the branch of hydrology that pertains to the study of lakes. Line Echo Wave Pattern (abbrev. LEWP) A radar echo pattern formed when a segment of a line of thunderstorms surges forward at an accelerated rate. Line Source An array of pollutant sources along a defined path that can be treated in dispersion models as an aggregate uniform release of pollutants along a line. Example: the sum of emissions from individual cars traveling down a highway can be treated as a line source. Compare area source and point source. Liquid Water Equivalent Same as Water Equivalent; the liquid content of solid precipitation that has accumulated on the ground (snow depth). The accumulation may consist of snow, ice formed by freezing precipitation, freezing liquid precipitation, or ice formed by the refreezing of melted snow. Lithometeor Atmospheric phenomena which affect the state of the atmosphere. They constitute dry particles that hang suspended in the atmosphere, such as dust, smoke, sand, and haze. Lithosphere In hydrologic terms, that part of the earth which is composed predominantly of rocks (either coherent or incoherent, and including the disintegrated rock materials known as soils and subsoils), together with everything in this rocky crust. Littoral Zone In hydrologic terms, the area on, or near the shore of a body water. Live Capacity In hydrologic terms, the total amount of storage capacity available in a reservoir for all purposes, from the dead storage level to the normal water or normal pool level surface level. Does not include surcharge, or dead storage, but does include inactive storage, active conservation storage and exclusive flood control storage. --- þ Synchronet þ The Thunderbolt BBS - wx1der.dyndns.org .