Weather Words - E | Weather | WGNTV.com | WGN TV

Weather Words - E

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1816 - The Year Without a Summer: Widespread snows in June across New England and southeast Canada, repeated frosts in July and August. Major crop failures. Known also as Eighteen hundred and froze to death.

Early hurricane: The annual Atlantic hurricane season runs from June 1 through November 30. Any named tropical cyclone that forms during the preceding three months (March, April, May) is considered to be an early storm and it will be named from the upcoming season's list.

Early radioactive fallout: Radioactive debris that rises into the atmosphere and falls to earth within 24 hours after a nuclear explosion. Because it remains in the atmosphere for such a short time, it is highly radioactive.

Earth: The third planet from the sun and our home. It's not a perfect sphere: The equatorial circumference of the Earth is 24,901.55 miles, and the polar circumference is 24,859.82 miles, or 41.73 miles less.

Earth's atmosphere: A mixture of several gases: nitrogen (78 percent), oxygen (21 percent), argon (1 percent), carbon dioxide (0.03 percent) and several trace gases. Water vapor is a variable constituent (up to 4 percent).

Earth tide: Movement of the solid Earth due to the gravitational pull of the moon and sun, and greatest when the moon is directly overhead: The earth rises about one foot.

Earthlight: The faint illumination on the dark part of the moon's disk produced by sunlight reflected onto the moon from the Earth's surface and atmosphere; also called earthshine.

Earthquake: The vibration or movement of a portion of the Earth's surface. It is not a meteorological event and has no known atmospheric or weather consequences.

Earthquake duration: The average strong U.S. earthquake lasts about 30 seconds. The magnitude 9.2 Alaskan earthquake on March 27, 1964 (the most powerful U.S. quake) lasted almost seven minutes. It caused great damage in Anchorage and southern Alaska.

Earthquake hazard: In the last century, nearly one million people died in earthquakes; in this century, it is feared ten million might die because of much larger populations in earthquake-vulnerable areas. Most vulnerable regions: the Pacific rim, the Mid-East.

Earthquake weather: Weather conditions that supposedly cause earthquakes. The belief, now discredited, was that hot, calm weather caused earthquakes, as did cloudy, calm weather. The concept of earthquake weather originated with Aristotle in the 4th Century B.C.

Earthquake, world's most powerful: The May 22, 1960, quake centered beneath the Pacific Ocean 100 miles off the coast of southern Chile. It registered an awesome magnitude 9.5.

Earthshine: The faint illumination on the dark part of the moon's disk produced by sunlight reflected onto the moon from the Earth's surface and atmosphere; also called earthlight.

Easterly wave: An area of weak low pressure that forms over North Africa and drifts to the west over the tropical North Atlantic Ocean, carried along by a belt of prevailing easterly winds that exists just to the north of the Equator. About 60 waves are generated over North Africa each year and a few intensify into hurricanes.

Easterly waves: Areas of weak low pressure that form over North Africa and drift to the west over the tropical North Atlantic Ocean. They often serve as seeding circulations for hurricanes.

Eastland disaster: The steamer Eastland capsized on July 24, 1915, between the Clark and LaSalle Street bridges in the Chicago River; 835 deaths (worst Great Lakes ship disaster). The steamer was unstable and this event was not weather related.

Echo: A general term for the appearance on a radar display of the radio signal reflected from a target, usually precipitation particles or very large cloud particles.

Echoes: Precipitation patterns displayed on radars, so-called because, like reflected sound echoes, they result from the radar beam reflecting off precipitation particles and returning to the radar.

Ecology: The study of the mutual relations between organisms and their environment.

Ecosystem: Organisms and the environment (including the weather) in which they interact. The definition is sometimes extended to include the actual processes of interaction.

Eddy: A current in water or in air that moves contrary to the direction of the main current, and often in a circular motion. Atmospheric and oceanic eddies can be hundreds of miles in diameter.

Edmund Fitzgerald: On Nov. 10, 1975, the 729-foot ore freighter Edmund Fitzgerald sank at 7:10 p.m. during a violent Lake Superior storm that brought 70 m.p.h. winds and 30-foot waves. All on board (29) were lost.

Edmund Fitzgerald disaster: On November 10, 1975, the 729-foot ore freighter Edmund Fitzgerald sank at 7:10 p.m. during a violent Lake Superior storm that brought 70 m.p.h. winds and 30-foot waves. All on board (29) were lost.

El Cordonazo: The remnants of a rare West Coast hurricane swept onshore south of Los Angeles on Sept. 25, 1939. El Cordonazo brought 5 to 12 inches of rain across the city area; 45 lives were lost at sea.

El Niño: A widespread warming of the surface waters of the eastern tropical Pacific Ocean. It results in heavy rainfall on coastal Ecuador and Peru, and suppresses the upwelling of nutrient-rich waters in the region. It causes changes in planetary wind patterns that have major effects, many not yet understood, on global weather.

El Niño/La Niña: A widespread warming of the surface waters of the eastern tropical Pacific Ocean. La Niña: A widespread cooling of the surface waters of the eastern tropical Pacific Ocean.

Electromagnetic pulse (EMP): The burst of electromagnetic radiation released during a nuclear blast above the surface. EMP is possibly capable of burning out electronic circuitry hundreds of miles from the site of an air burst.

Endoreic: Referring to a region of interior drainage; a region whose water drains to interior lakes and is lost only by evaporation, but otherwise never returns to the oceans. About 5% of North America is endoreic.

Endoreic region: A region whose surface drainage (rivers, streams) does not reach the oceans. Portions of the intermountain west of the U.S. are endoreic.

Enhanced greenhouse effect: The strengthening of the atmosphere's natural greenhouse effect due to the addition to the atmosphere of significant amounts of heat-trapping gases that result from man's activities.

Ensemble forecast: A weather forecast based upon an average of many forecasts created by running the same computer model with slightly different initial (starting) conditions.

Entrainment: The mixing of environmental air into an organized current of air. The term is often applied to the mixing of air into clouds, especially cumulus clouds, or the currents feeding into cumulus clouds.

Entrance Region: The region upstream from a wind speed maximum in a jet stream, in which air is approaching (entering) the region of maximum winds, and therefore is accelerating.

Environment: External conditions and surroundings, especially those that affect the quality of life of plants, animals and human beings.

Environment Canada: Canada's weather service, created in 1871; it provides a wide array of environmental information for Canada, including daily weather forecasts, warnings of severe storms, smog advisories and the ultra-violet index.

Environmental quality: Small efforts can make a difference in our environment: Plant a tree. Trees moderate temperatures, help break the wind, reduce airborne pollution and are visually pleasing.

Eolian: (also aeolian) Pertaining to the action or the effect of the wind, as in eolian sounds or eolian deposits of sand. The word is derived from the name of the Greek god of the winds, Aeolus.

Ephemeral stream: A stream or stream channel that carries water only during or immediately after periods of rain or snowmelt.

Epilimnion: The upper warm layer of a body of water with thermal stratification (like Lake Michigan), which extends down from the surface to the thermocline (top of layer of colder water beneath).

Equator: The imaginary great circle of 0 degrees latitude on the Earth's surface, equidistant from the north and south poles, separating the Northern Hemisphere from the Southern Hemisphere.

Equinoctial storms: Severe storms that are popularly believed to accompany the vernal (around Mar. 21) and autumnal (around Sep. 21) equinoxes. There is no evidence the occurrence of an equinox has meteorological implication.

Equinox: The moment the center of the sun crosses the celestial equator (the projection of the Earth's equator into space). Spring and autumn equinoxes occur, respectively, about March 21 and Sept. 22.

Erosion: The movement of soil or rock from one place to another by the action of the sea, running water, moving ice, precipitation, or wind.

Escape velocity: The lowest speed that an object moving directly outward from an astronomical body must have in order to escape its gravitational pull. The Earth's escape velocity: about 25,000 m.p.h.

Estivation: A sleeplike state that some animals enter in summer. Their metabolic rate slows and they become inactive, permitting survival during long periods of high temperatures and diminished water supply.

Ether: A medium of transmission of light and heat, once believed to pervade all space, including the interior of all solid bodies. The existence of ether is no longer accepted.

Euphotic zone: The near-surface layer of a body of water that receives ample sunlight to support plant photosynthesis. The layer is typically the top 240 feet, but this varies with sun angle, length of day and cloudiness.

Europe's highest temperature: On this date (August 4) in 1881, the temperature at Seville, Spain, rocketed to 122 degrees F, the highest temperature ever recorded on the continent of Europe.

Europe's lowest temperature: -67 degrees F at Ust'Shchugor, Russia, in January. The U.S. National Climatic Data Center recognizes the validity of this temperature, but the date and year are unknown.

Evaporation: The physical process by which a liquid (like water) or solid (like ice) is transformed to the gaseous state; the opposite of condensation.

Evaporation of ocean water: 80,000 cubic miles of water evaporate each year from the oceans. Of that evaporated water, 24,000 cubic miles of it falls on the continents as rain and snow. The rest falls directly back into the oceans.

Evaporation pan: A pan used to hold water during observations for the determination of the amount of evaporation at a given location. Such pans are of varying sizes and shapes.

Evapotranspiration: The addition of water vapor to the atmosphere through evaporation from wet surfaces and from the release of water vapor by plants. Evapotranspiration is an important process in the modification of dry air masses.

Ever-changing weather: A term used to stress the importance of different aspects of the weather that are constantly changing as they move, rather than moving unchanged.

Exhalation: The escape of radioactive gases (radon, thoron, actinon) from surface layers of soil or loose rock into the atmosphere.

Exosphere: Beginning at about 400 miles above the Earth's surface, it is the uppermost layer of the earth's atmosphere; the only layer of the atmosphere from which atmospheric gases can escape into outer space.

Explosive cyclogenesis: Sudden, extremely rapid intensification of a low pressure system; it occurs most often just off the U.S. Atlantic Coast or, more rarely, in the western Great Lakes region.

Exposure: The method of presentation of a weather instrument (like a thermometer) to that element which it is destined to measure; also, the situation of a weather station with regard to the phenomena to be observed there.

Exsiccation: The drying up of an area by the removal of moisture. It implies some change, frequently the result of human activity, that decreases available moisture without any change in precipitation.

Extratropical: Descriptive of a tropical cyclone that has lost its tropical characteristics. It implies both movement of the storm into mid latitudes and a transition of the storm's energy source from heat released by condensation of water vapor to cold frontal process.

Eye: The roughly circular central area of comparatively light winds and fair weather of a hurricane. Eye diameters are usually 10-25 miles. Over the ocean, the sea in the eye is very turbulent: high waves and confused wave patterns.

Eye of wind: A nautical expression indicating the direction from which the wind is blowing. More generally, wind direction is always stated as the direction from which the wind is blowing.

Eye wall: A ring of cumulonimbus clouds that, by definition, must encircle half or more of the eye of a tropical cyclone. The eye wall contains the storm's highest winds and most intense rains, but lightning is rare.