Weather terms starting with H

147 terms

H-Alpha In solar-terrestrial terms, this absorption line of neutral hydrogen falls in the red part of the visible spectrum and is convenient for solar…
H-component of the Geomagnetic Field (Geomagnetic Elements) In solar-terrestrial terms, the components of the geomagnetic field at the surface of the earth.
H0 On a buoy report, Significant Wave Height is the average height (meters) of the highest one-third of the waves during a 20 minute sampling period.
H5 500 millibar level height (in a standard atmosphere this is near 5,500 meters (18,000 ft)
H7 height of the 700 millibar level. In a standard atmosphere this is near 3,000 meters (10,000 ft)
H8 height of the 850 millibar level.
Hague Line The North Atlantic boundary between the U.S. and Canada fishing waters as determined by the World Court in The Hague, Netherlands.
Hail Showery precipitation in the form of irregular pellets or balls of ice more than 5 mm in diameter, falling from a cumulonimbus cloud.
Hail Contamination A limitation in NEXRAD rainfall estimates whereby abnormally high reflectivities associated with hail are converted to rainfall rates and rainfall…
Hail Index An indication of whether the thunderstorm structure of each storm identified is conducive to the production of hail.
Hail Size Typically refers to the diameter of the hailstones. Warnings and reports may report hail size through comparisons with real-world objects that correspond…
Hail Spike An area of reflectivity extending away from the radar immediately behind a thunderstorm with extremely large hail.
hailstones Transparent or partially opaque particles of ice that range in size from that of a pea to that of golf balls.
Haines Index This is also called the Lower Atmosphere Stability Index. It is computed from the morning (12Z) soundings from RAOB stations across North America.
Half-life The time in which half the atoms of a particular radioactive nuclide disintegrate. The half-life is a characteristic property of each radioactive isotope.
haline related to salt.
Halo Any of a variety of bright circles or arcs centered on the sun or moon, caused by the refraction or reflection of light by ice crystals suspended in the…
Halocarbons Compounds containing either chlorine, bromine or fluorine and carbon. Such compounds can act as powerful greenhouse gases in the atmosphere.
Halons Compounds, also known as bromofluorocarbons, that contain bromine, fluorine, and carbon.
Hanging (ice) dam A mass of ice composed mainly of frazil or broken ice deposited underneath an ice cover in a region of low flow velocity.
Hazardous Weather Outlook A narrative statement produced by the National Weather Service, frequently issued on a routine basis, to provide information regarding the potential of…
Hazards Assessment CPC's Hazards Assessment provides emergency managers, planners, forecasters and the public advance notice of potential hazards related to climate, weather…
Haze (abbrev. HZ)- An aggregation in the atmosphere of very fine, widely dispersed, solid or liquid particles, or both, giving the air an opalescent appearance…
HDD Heating Degree Days- A form of degree day used to estimate energy requirements for heating.
HDRAIN An Hourly Digital Rainfall Product of the WSR-88D.
Head The upper horizontal part of a window frame or window opening.
Head Loss The energy lost from a flowing fluid due to friction, transitions, bends, etc.
Head Race A channel which directs water to a water wheel; a forebay.
Headward Erosion Erosion which occurs in the upstream end of the valley of a stream, causing it to lengthen its course in such a direction.
Headwater Basin A basin at the headwaters of a river. All discharge of the river at this point is developed within the basin.
Headwaters Streams at the source of a river.
Heat Pressure and intimidation used by a casino to discourage card counters.
Heat Advisory Issued within 12 hours of the onset of the following conditions: heat index of at least 105°F but less than 115°F for less than 3 hours per day, or…
Heat Balance Energy output from a system that equals energy input.
Heat balance of the Earth-atmosphere system Heat balance of the Earth-atmosphere system The equilibrium that exists on the average between the radiation received by the Earth and atmosphere from the…
Heat budget Heat budget Relation between fluxes of heat into and out of a given region or body and the heat stored by the system.
heat capacity The ratio of the heat absorbed (or released) by a system to the corresponding temperature rise (or fall).
Heat Content The amount of heat in a quantity of matter at a specific temperature and pressure.
Heat Exhaustion A mild form of heat stroke, characterized by faintness, dizziness, and heavy sweating.
Heat flux Heat flux Amount of heat, transferred in a liquid, in particular in the atmosphere, per unit of time through a unit area.
Heat Index The Heat Index (HI) or the "Apparent Temperature" is an accurate measure of how hot it really feels when the Relative Humidity (RH) is added to the actual…
heat index (HI) An index that combines air temperature and relative humidity to determine an apparent temperature-how hot it actually feels.
Heat Lightning Lightning that occurs at a distance such that thunder is no longer audible.
Heat Sink A structure or media that absorbs heat.
Heat Source A structure or media from which heat can be absorbed or extracted.
Heat Stroke A condition resulting from excessive exposure to intense heat, characterized by high fever, collapse, and sometimes convulsions or coma.
Heat Wave A period of abnormally and uncomfortably hot and unusually humid weather. Typically a heat wave lasts two or more days.
Heating Degree Days (abbrev. HDD) A form of degree day used to estimate energy requirements for heating.
Heavy Freezing Spray An accumulation of freezing water droplets on a vessel at a rate of 2 cm per hour or greater caused by some appropriate combination of cold water, wind…
Heavy Freezing Spray Warning A warning that may be issued within the Offshore Waters Forecast, the Coastal Waters Forecast, the Nearshore Marine Forecast, and the Open Lake Forecast…
Heavy Snow This generally means... snowfall accumulating to 4" or more in depth in 12 hours or less; or snowfall accumulating to 6" or more in depth in 24 hours or…
Heavy Snow Warning Issued by the National Weather Service when snowfall of 6 inches (15 cm) or more in 12 hours or 8 inches (20 cm) or more in 24 hours is imminent or…
Heavy Surf Advisory An advisory issued by the National Weather Service for fast moving deep water waves which can result in big breaking waves in shallow water (the surf…
Hectopascal A unit of pressure equal to a millibar (1 hPa = 1 mb). Abbreviated hPa.
Height In meteorology, usually a reference to Geopotential Height; roughly the height above sea level of a pressure level.
Heinrich Events periods of increased discharge of icebergs from the margin of ice sheets into the North Atlantic Ocean during the last glacial.
Helicity A property of a moving fluid which represents the potential for helical flow (i.e. flow which follows the pattern of a corkscrew) to evolve.
Hertz A measure of the number of cycles or wavelengths of electrical energy per second; U.S. electricity supply has a standard frequency of 60 hertz.
HI High- In meteorology, a region of high pressure; also known as anticyclone.
HIC Hydrologist In Charge
High (abbrev. HI)- In meteorology, a region of high pressure; also known as anticyclone.
High Clouds These clouds have bases between 16,500 and 45,000 feet in the mid latitudes. At this level they are composed of primarily of ice crystals.
High Energy Event In solar-terrestrial terms, flares (class two or more) with outstanding Centimetric Bursts and SID.
High Frequency (HF) The portion of the radio frequency spectrum between between 3 and 30 MHz
High Latitudes With specific reference to zones of geomagnetic activity, "high latitudes" refers to 50Âº to 80Âº geomagnetic.
High Risk (of severe thunderstorms) Severe weather is expected to affect more than 10 percent of the area. A high risk is rare, and implies an unusually dangerous situation and usually the…
High Seas Forecast (HSF) - Marine forecasts for the major oceans of the world. In this context, major gulfs or seas (e.g.
High Surf Large waves breaking on or near the shore resulting from swells spawned by a distant storm.
High Surf Advisory A High Surf Advisory is issued when breaking wave action poses a threat to life and property within the surf zone. High surf criteria vary by region.
High Surf Warning A High Surf Warning is issued when breaking wave action results in an especially heightened threat to life and property within the surf zone.
High Wind Sustained wind speeds of 40 mph or greater lasting for 1 hour or longer, or winds of 58 mph or greater for any duration.
High Wind Advisory This product is issued by the National Weather Service when high wind speeds may pose a hazard. The criteria for this advisory varies from state to state.
High Wind Warning This product is issued by the National Weather Service when high wind speeds may pose a hazard or is life threatening.
High Wind Watch This product is issued by the National Weather Service when there is the potential of high wind speeds developing that may pose a hazard or is life…
High-level clouds High-level clouds Cirrus, Cirrocumulus and Cirrostratus are high-level clouds.
High-Speed Stream In solar-terrestrial terms, a feature of the solar wind having velocities that are about double average solar wind values.
Higher heating value Quantity of heat liberated by the complete combustion of a unit volume or weight of a fuel assuming that the produced water vapor is completely condensed…
Hinge Crack Crack caused by significant changes in water level.
Histosol Wet organic soils, such as peats and mucks.
HLS Hurricane Local Statement
HMD (Hemispheric Map Discussion)- This discussion is issued once a day around 1 PM EST (2 PM EDT) and is primarily intended to provide insight into the…
HND Hundred
Hoar Frost A deposit of interlocking crystals formed by direct sublimation on objects, usually those of small diameter freely exposed to the air, such as tree…
Hoarfrost Hoarfrost A deposit of interlocking ice crystals (hoar crystals) formed by direct sublimation on objects, usually those of small diameter freely exposed…
Hodograph A polar coordinate graph which shows the vertical wind profile of the lowest 7000 meters of the atmosphere.
Holocene epoch an epoch of the Quaternary period dating from the end of the Pleistocene approximately 11,500 years ago until the present.
Homologous Flares In solar-terrestrial terms, solar flares that occur repetitively in the same active region, with essentially the same position and with a common pattern…
Hook Echo A radar reflectivity pattern characterized by a hook-shaped extension of a thunderstorm echo, usually in the right-rear part of the storm (relative to its…
Horizon The distant line along with the earth and sky appear to meet. Obstructions are not considered as part of the horizon.
horizontal wind The horizontal wind in terms of either speed and direction, or the zonal (u) and meridional (v) components.
Hourly Precipitation Data (HPD) It contains data on nearly 3,000 hourly precipitation stations (National Weather Service, Federal Aviation Administration, and cooperative observer…
HP Storm or HP Supercell - High-Precipitation storm (or High-Precipitation supercell). A supercell thunderstorm in which heavy precipitation (often including hail)…
HPA Hectopascal- A unit of pressure equal to a millibar (1 hPa = 1 mb).
HPC Hydrometeorological Prediction Center
HR Hour
HRS hours
HSA (Hydrologic Service Area) A geographical area assigned to Weather Service Forecast Office's/Weather Forecast Office's that embraces one or more rivers.
Humidity A measure of the moisture content of air; may be expressed as absolute, mixing ratio, saturation deficit, relative, or specific.
Humidity Recovery The change in relative humidity over a given period of time; generally between late evening and sunrise.
Hummock A hillock of broken ice which has been forced upward by pressure.