wise sense (north to northwest to west, for example).
barometer — an instrument that measures atmospheric pressure. The two most common barometers are the mercury barometer and the aneroid barometer.
blizzard — a severe weather condition characterized by low temperatures and strong winds (greater than 32 mph) bearing a great amount of snow.
Celsius scale — a temperature scale where (at sea level) water freezes at 0° and boils at 100°.
cold front — a transition zone where a cold air mass advances and replaces a warm air mass.
cold wave — a rapid fall in temperature within 24 hours that often requires increased protection for agriculture, industry, commerce, and human activities.
convection — atmospheric motions that are predominantly vertical, such as rising air currents due to surface heating. The rising of heated surface air and the sinking of cooler air aloft is often called free convection.
cyclone — an area of low pressure around which the winds blow counterclockwise in the Northern hemisphere and clockwise in the Southern hemisphere.
daily range of temperature — the difference between the maximum and minimum temperatures for any given day.
dew — water that has condensed onto objects near the ground when their temperatures have fallen below the dew point of the surface air.
dew point
dew point falls below freezing, it is called the frost point.
downburst — a severe localized downdraft that can be experienced beneath a severe thunderstorm.
drizzle — small drops between 0.2 and 0.5
mmin diameter that fall slowly and reduce visibility more than light rain.
drought — a period of abnormally dry weather sufficiently long enough to cause serious effects on agriculture and other activities in the affected area.
dry line — a boundary that separates warm, dry air from warm, moist air. It usually represents a zone of instability along which thunderstorms form.
evaporation — the process by which a liquid changes into a gas.
extratropical cyclone — a cyclonic storm that most often forms along a front in middle and high latitudes. Also called a middle latitude storm, a depression, and a low. It is not a tropical storm or hurricane.
eye — a region in the center of a hurricane (tropical storm) where the winds are light and skies are clear to partly cloudy.
eye wall — a wall of dense thunderstorms that surrounds the eye of a hurricane.
Fahrenheit scale — a temperature scale where (at sea level) water freezes at 32° and boils at 212°.
fog — a cloud with its base at the earth’s surface. It reduces visibility to less than 1 mile (1.6 km).
freeze — the condition that exists when the surface temperature over a widespread area remains below freezing (32° F or 0° C) for a sufficient time to constitute the characteristic feature of the weather. If the freeze cuts
28 | Special Features |