Descriptionary

Bermuda high in the North Atlantic off North America, a migrating, subtropical area of high pressure.

blue jet similar to a sprite, a blue electrical dis­charge whose flash appears over a thunderstorm, 25 to 30 miles (40-48 km) above Earth.

bust meteorologist's slang for an inaccurate forecast.

Celsius scale by which temperature is measured in many areas outside of the United States. The freez­ing point is 0 degrees and the boiling point is 100 degrees.

condensation the change of a substance from a vapor to a liquid; the opposite of evaporation.

convection the transfer of heat by the vertical motion of air.

depression an area of low pressure.

dew point the temperature at which air becomes saturated; a further drop in temperature causes con­densation followed by precipitation.

Doppler radar more accurately referred to as pulse- Doppler radar, a radar system that reads returned echoes to detect the presence, speed, and direction of precipitation, whether rain, hail, or snow.

El Nino taken from the Spanish for "the child," since it usually appears during Christmastime, it is a unusually warm flow of water from the Pacific Ocean toward South America.

eye of the storm circular area of light winds and fair weather in the center of tropical storms.

Fahrenheit scale used to measure temperature in the United States. Freezing is 32 degrees and the boil­ing point is 212 degrees.

fair descriptive term for clear, pleasant, and largely windless weather.

front the line of divergence between air masses of different characteristics.

fulmineous referring to thunder.

heat lightning an erroneous term. Heat lightning is normal lightning that flashes at such a great distance that its thunder cannot be heard.

heat wave very hot and humid weather that lasts for two days or more.

high a high-pressure system, usually associated with fair weather.

Indian summer any unusually warm period in the middle of autumn.

La Nina a periodic cooling of the surface waters of the Pacific off the coast of South America, which causes changes in weather patterns elsewhere in the world.

lightning a powerful electrical discharge, reaching temperatures of 54,000 degrees Fahrenheit (29,982° C) and carrying 40 kiloamperes (40,000 amperes) of electric current or more; most often released during a thunderstorm, from cloud to cloud, from cloud to air, or from cloud to ground. Lightning bolts can stretch anywhere from 1 mile to more than 100 miles in length. The near-instant superheating of the surround­ing air creates a shock wave that produces thunder.

lightning rod a conductive metal rod erected over the roof of a building to attract lightning and draw it safely down into the ground.

low a region of low pressure, often associated with precipitation and windy conditions.

meteorologist one who is trained to forecast the weather.

radiosonde installed in a weather balloon, an instru­ment or probe that measures altitude, atmospheric pressure, temperature, humidity, and wind speed and radios the data to a ground computer. A type of radio­sonde known as an ozonesonde measures ozone.

ridge an elongated area of high barometric pressure.

sheet lightning an erroneous term. Sheet lightning is actually normal lightning, but the bolt is obscured by distance and cloud cover, resulting in a broad flash that reflects for great distances.

sprite any large, reddish-orange, electrical discharge whose flash appears 25 to 60 miles (40-96 km) above a thunderstorm.

storm surge the raising of shoreline water level by storm winds; also known as storm tide or storm wave.

super cell the most powerful and long-lasting type of thunderstorm, characterized by a continuously rotating updraft that generates not only heavy rain, hail, and wind but may also spawn tornadoes and dangerous downdrafts.

temperature inversion a flipping of normal atmo­spheric conditions, when air that is normally cold at higher elevations is actually warm, while cold air stays at low elevations. Inversions, which can trap smog close to the ground and sometimes spawn thunder­storms, are caused by less dense warm air masses mov­ing over dense, cool ones, but they can occur simply when the Sun goes down or when the Sun is low on the horizon, as in winter.

transient luminous event any electrical discharge, including sprites and blue jets, occurring in the upper atmosphere.

trough an elongated area of low pressure.

weather balloon a hydrogen-filled balloon that car­ries instruments to high altitude to measure atmo­spheric pressure, temperature, humidity, wind speed, and, sometimes, ozone levels. Also known as a sound­ing balloon.

whistler a descending whistling noise heard over the radio and caused by lightning.

mountains