Weather Maps and Cloud Formation

evaporation fog

forms when water vapor is added to air.

condensation nuclei

particles that serve as surfaces onto which water vapor condenses.

clouds

water droplets or ice suspended in the atmosphere.

Isobars

lines that connect locations of the same pressure.

dew point

the atmospheric temperature (varying according to pressure and humidity) below which water droplets begin to condense and dew can form.

warm fronts

the changeover region where a warm air mass is replacing a cold air mass. Causes steady, light rain (long lived), followed by warm temperatures.

stationary fronts

two air masses meet and neither advanced into the other's territory. Winds blow in parallel but opposite directions. Clouds form on either side. Precipitation may fall in the same place for long periods, or may not fall at all.

air mass

A huge body of air that has similar temperature, humidity, and air pressure at any given height.

high-pressure area

An area that is relatively cold and dry.

low-pressure area

An area that is relatively warm and moist.

trough

An elongated area of low pressure, denoted by a dashed line. Precipitation usually occurs on the eastern side as warm air rises.

low level clouds

Are those that form below 6,500 ft. Usually thick and obscure the sky. Are rich in moisture and usually result in precipitation.

midlevel clouds

Are those that form between 6,500 and 20,000 ft. diffuse light from the moon and sun, thereby creating fuzzy discs, but they do not totally block light from these objects. Have more moisture than high-level clouds and can lead to light snow or light rain.

localized convection

Areas of the ground heat unevenly, and small pockets of hot air above the hot spots rise.

Fronts

Areas where cold and warm air masses meet. The narrow region separating the two air masses of different densities.

upslope fog

As air rises along a mountain, a fog forms like a cloud near the mountain slope.

fog

Is a cloud that happens at ground level. Classified by how it forms.

Isotherms

Lines joining places that have the same temperature.

cold fronts

The changeover region where a cold air mass is replacing a warmer air mass. Causes thunderstorms and heavy rains (short lived), followed by cooler temperatures.

high clouds

Thin and relatively dry. They consist mainly of ice crystals and do not produce precipitation.

Convergence

Two airflows collide head-on, forcing air upward.

occluded fronts

Two cold air masses meet with a warm air mass sandwiched aloft, denoted by purple semi-circles and triangles on the same side of a line. Causes heavy precipitation, and cooler air follows the front.

frontal wedging

Warm, moist air rises over cold, dense air, which happens at frontal boundaries.

orographic uplift

When airflow confronts a mountain barrier, the air rises.

radiation fog

When the ground cools rapidly (radiative cooling), it cools the air immediately above it below the dew point, and a fog forms.

advection fog

When warm, moist air blows over a cold surface (land or water), fog forms.

Surface weather maps

a special type of weather map that provides a view of weather elements over a geographical area at a specified time based on information from ground-based weather stations.

clouds of vertical development

clouds that stretch through multiple altitudes within the atmosphere.