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Hurricanes: Science and Society
Glossary - L
La Nina
La Nina, a phase of ENSO, is a periodic cooling of surface ocean waters in the eastern tropical Pacific along with a shift in convection in the western Pacific further west than the climatological average. These conditions affect weather patterns around the world. The preliminary CPC definition of La Nina is a phenomenon in the equatorial Pacific Ocean characterized by a negative sea surface temperature departure from normal. Source: NOAA-NWS
The intersection of the surface center of a tropical cyclone with a coastline. Because the strongest winds in a tropical cyclone are not located precisely at the center, it is possible for the strongest winds in a cyclone to be experienced over land even if landfall does not occur. Similarly, it is possible for a tropical cyclone to make landfall and have its strongest winds remain over the water. Compare direct hit, indirect hit, and strike. Source NOAA-NHC.
A wide range of ground movement, such as rock falls, deep failure of slopes, and shallow debris flows. Although gravity acting on an over-steepened slope is the primary reason for a landslide, there are other contributing factors including: erosion by rivers, glaciers, or ocean waves create oversteepened slopes; rock and soil slopes are weakened through saturation by snowmelt or heavy rains; earthquakes create stresses that make weak slopes fail; earthquakes of magnitude 4.0 and greater have been known to trigger landslides; volcanic eruptions produce loose ash deposits, heavy rain, and debris flows; excess weight from accumulation of rain or snow, stockpiling of rock or ore, from waste piles, or from man-made structures may stress weak slopes to failure and other structures. Source: USGS
The angular distance north or south from the equator. Source: NASA
lead times
The length of time between the issuance of a forecast and the occurrence of the phenomena that were predicted. Source: (c) 1999, American Meteorological Society. Used with permission.
long wave radiation
A term used loosely to describe heat radiation emitted by the earth and atmosphere at wavelengths greater than about 4?m (greater than that of visible light). Source: (c) 1999, American Meteorological Society. Used with permission.
loop current
The passage of warm water through the Gulf of Mexico from the Yucatan Strait to the Straits of Florida and the connection between the Caribbean and Florida Currents. The Loop Current is part of the western boundary current system of the North Atlantic subtropical gyre and as such, is swift flowing, extending to great depth, and prone to instabilities. Its path includes a large northward excursion into the Gulf beyond 27°N but retreats to 25°N when shedding an eddy. Eddies drift slowly westward into the central and western Gulf of Mexico. Source: (c) 1999, American Meteorological Society. Used with permission.
low-pressure system
An area of a relative pressure minimum that has converging winds and rotates in the same direction as the earth. This is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Also known as an cyclone, it is the opposite of an area of high pressure, or a anticyclone. Source: NOAA-NWS