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Hurricanes: Science and Society
Glossary - H
H
halocline
A layer of water in which the salinity increases rapidly with depth. The principal haloclines in the ocean are either seasonal, due to freshwater inputs, or permanent.
hardwood hammocks
A dense stand of broad-leafed trees that grow on a natural rise of only a few inches in elevation.
heat waves
Periods of abnormally and uncomfortably hot and usually humid weather. To be a heat wave such a period should last at least one day, but conventionally it lasts from several days to several weeks. In 1900, A. T. Burrows more rigidly defined a “hot wave” as a spell of three or more days on each of which the maximum shade temperature reaches or exceeds 90°F. More realistically, the comfort criteria for any one region are dependent upon the normal conditions of that region. In the eastern United States, heat waves generally build up with southerly winds on the western flank of an anticyclone centered over the southeastern states, the air being warmed by passage over a land surface heated by the sun. Source: (c) 1999, American Meteorological Society. Used with permission.
hemisphere
Half of the Earth, usually conceived as resulting from the division of the globe into two equal parts, north and south or east and west.
herbaceous
Having the texture, color or appearance of a leaf, with little or no woody tissue. Source: State of Florida
high wind warning
A high wind warning is defined as 1-minute average surface winds of 35 kt (40 mph or 64 km/hr) or greater lasting for 1 hour or longer, or winds gusting to 50 kt (58 mph or 93 km/hr) or greater regardless of duration that are either expected or observed over land. Source NOAA-NHC.
high-pressure
An elongated area of relatively high atmospheric pressure, generally associated with light winds and dry weather, and almost always correlated with and most clearly identified as an area of anticyclonic wind flow.
horizontal boundary condition
A set of mathematical conditions to be satisfied, in the solution of a differential equation, at the edges or physical boundaries (including fluid boundaries) of the region in which the solution is sought. The nature of these conditions is usually determined by the physical nature of the problem, and is a necessary part of the complete formulation of the problem. Common boundary conditions for the atmosphere are that the velocity component normal to the surface of the earth vanish, and that the individual derivative of pressure vanish at the upper surface. The term is also used in the context of the time evolution of an open dynamical system that interacts with other external systems. The state of the external systems must be specified as a boundary condition to infer the evolution of the dynamical system under consideration. For example, the evolution of the atmospheric state of the earth requires the specification of sea surface temperature as a boundary condition. Source: (c) 1999, American Meteorological Society. Used with permission.
humidity
The amount of water vapor in the atmosphere. Source: NOAA-NWS ERH
hurricane
A tropical cyclone with maximum sustained winds of 119 km/h (74 mph) or greater. The term “hurricane” is used for Northern Hemisphere tropical cyclones east of the International Dateline to the Greenwich Meridian. The term “typhoon” is used for Pacific tropical cyclones north of the equator, west of the International Dateline. Hurricanes are further designated by categories on the Saffir-Simpson Scale. Hurricanes in categories 3, 4, 5 are known as “major” or “intense” hurricanes.
hurricane buoys
Buoys deployed to measure wind, wave, barometric pressure and temperature data to help the NOAA Tropical Prediction Center more accurately determine formation or dissipation, extent of wind circulation, maximum intensity and center location of the tropical cyclones. In addition, direction, height and distribution of ocean waves generated by hurricane activity are be measured. Beyond their measurements of tropical cyclones, the buoys also provide year-round data for analysis and forecasts of other marine disturbances. Data from the buoys, some as large as 12-meters wide, is used to validate the quality of measurements and estimates obtained from remote-sensing reconnaissance aircraft and satellites, and National Weather Service forecasts. Source: NOAA Public Affairs
hurricane season
The portion of the year having a relatively high incidence of hurricanes. The hurricane season in the Atlantic, Caribbean, and Gulf of Mexico runs from June 1 to November 30. The hurricane season in the Eastern Pacific basin runs from May 15 to November 30. The hurricane season in the Central Pacific basin runs from June 1 to November 30. Source NOAA-NHC.
hurricane warning
An announcement that hurricane conditions (sustained winds of 118 km/h [74 mph] or higher) are expected somewhere within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds. Source NOAA-NHC.
hurricane watch
An announcement that hurricane conditions (sustained winds of 118 km/h [74 mph] or higher) are possible within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds. Source NOAA-NHC.
hurricane’s primary circulation
The prevailing fundamental atmospheric circulation on a planetary scale that must exist in response to 1) radiation differences with latitude, 2) the rotation of the earth, and 3) the particular distribution of land and oceans; and that is required from the viewpoint of conservation of energy. Primary circulation and general circulation are sometimes taken synonymously. They may be distinguished, however, on the basis of approach; that is, primary circulation is the basic system of winds, of which the secondary and tertiary circulation are perturbations, while general circulation encompasses at least the secondary circulations. Source: (c) 1999, American Meteorological Society. Used with permission.
hurricane’s secondary circulation
1. Atmospheric circulation features of cyclonic scale. Use of the term is usually reserved for distinguishing between the various dimensions of atmospheric circulation, that is, primary circulation, tertiary circulation. See also general circulation.2. A circulation induced by the presence of a stronger circulation as a result of dynamical constraints. A frictional secondary flow is an example. 3. Organized flow superimposed on a larger-scale mean circulation. For example, roll vortices are a secondary circulation in the atmospheric boundary layer. They “fill” the boundary layer vertically, but have a width of only two to three times the boundary layer depth, while the mean wind profile extends over a much broader region. Source: Glossary of Meteorology. (c)American Meteorological Society. Reprinted with permission.
hydrogen bonds
The attractive force between a hydrogen attached to an electronegative (attracts electrons) atom of one molecule and an electronegative atom of a different molecule. Usually the electronegative atom is oxygen, nitrogen, or fluorine. Hydrogen bonds that form between water molecules account for some of the essential properties of water (e.g. that it can be found in all three physical states, solid, liquid, and gas).
hydrologic analyses
The study of the waters of the earth with relation to the effects of precipitation and evaporation upon the water in streams, rivers, lakes, and its effect on land surfaces. Source: NOAA-NWS ERH
hypoxia
A condition where there is not enough oxygen in the water. This forces fish to either swim away or die and can suffocate plants living in the water. Hypoxia occurs when there are too many nutrients in the water. Source: US EPA