weather
the state of the atmosphere at a specific time and place. It includes such conditions as air pressure, wind, temperature, and moisture in the air. Because air and moisture move in the atmosphere, weather constantly changes. The interaction of air, water a
humidity
is the amount of water vapor in the air. Warmer air can hold more water vapor, tending to make it more humid.
relative humidity
is the amount of water vapor in the air compared to what it can hold at a specific temperature. It is given in a percentage. When air cools, it can't hold as much water vapor, so the water vapor condenses to a liquid or forms ice crystals. Warm air holds
dew point
is the temperature at which air is saturated and condensation forms. A cold drink cools the air around the container to its dew point. At its dew point, the water vapor in the air condenses and forms droplets on the container. Water can form on grass in t
fog
stratus clouds that form near the ground.
precipitation
is water falling from clouds. When water droplets in clouds combine and grow large enough precipitation falls to Earth. These droplets form around very small particles of dust or salt. Air temperature determines whether the droplets form rain, snow, sleet
air mass
a large body of air with properties like the part of Earth's surface over which it formed
front
a boundary between two different air masses. Clouds, precipitation, and storms occur at frontal boundaries. Where colder air advances under warm air you have a cold front. Where warmer air advances over colder air you have a warm front. Occluded fronts in
tornado
a violent, whirling wind that moves in a narrow path over land. They can be produced by thunderstorms. They are produced when wind at different heights blows in different directions and at different speeds.
hurricane
a large, swirling, low-pressure system that forms over tropical oceans. Most of these travel from east to west. These are the most powerful severe storms. Warm, moist air
blizzard
a winter snow storm with strong winds, cold temperatures, and low visibility, that lasts more than three hours.
meteorologist
studies and forecasts the weather using data gathered from many sources.
station model
shows weather conditions at a one specific location.
isotherm
are lines on a weather map connecting points of equal temperature.
isobar
are lines on a weather map that connect points of equal atmospheric pressure. Weather maps are drawn with these to keep track of high and low pressure areas.
anemometer
an instrument used to measure wind speed. They have rotating cups that spin faster when the wind is strong.
saturated air
When air holds all the water vapor it possibly can at a specific temperature.
stratus clouds
smooth, even sheets or layers at low altitudes. Low layered gray clouds that produce light precipitation.
cumulus clouds
masses of puffy, white clouds, often with flat bases, that form when air currents rise.
cirrus clouds
high, thin, white, feathery clouds made of ice crystals that are usually associated with fair weather but that can also indicate approaching storms.
cirro-
prefix or suffix used for high clouds
alto-
prefix or suffix used for middle-elevation clouds
strato-
prefix or suffix used for low clouds
cirrostratus clouds
high clouds that usually indicate fair weather but they can also signal an approaching storm. They are made of ice crystals.
nimbus
suffix/prefix for clouds that are dark and so full of water that sunlight can't penetrate them. Clouds producing rain or snow usually have the word 'nimbus' attached to them.
cumulonimbus cloud
When a cumulus cloud grows into a thunderstorm. These clouds can tower up to 18 KM high.
nimbostratus clouds
layered clouds that can bring long, steady, rain or snow falls.
cyclone
large, swirling areas of low pressure that are associated with stormy weather.
anticyclone
high pressure areas that are associated with fair weather.
wind
air moving in a specific direction. Air moves from high pressure areas to low pressure areas, causing this
barometer
an instrument that measures air pressure
Wind
Air moving in a specific direction
Condensation
Formation of liquid water from water vapor
Precipitation
Cloud droplets combine and grow large enough to fall to Earth
Temperature
Measurement of average amount of motion of molecules
Wind vane
Instrument of testing wind direction
Humidity
Amount of water vapor present in the air
Dew point
The temperature at which air is saturated and condensation forms
Air
Made up of molecules that are always moving randomly
Relative humidity
Amount of water vapor present in air compared to the amount needed for saturation at a specific temperature
Weather
State of the atmosphere at a specific time and place
Fog
A stratus cloud on the ground, forms when warm, moist air cools at ground level
Anemometer
Instrument for measuring wind speed
4 types of precipitation
Rain, snow, sleet, hail
3 types of clouds
stratus, cumulus, cirrus
Relationship between temperature and relative humidity
Relative humidity increases as temperature decreases, or relative humidity decreases as temperature increases
Weather at a cold front
Clouds & precipitation; possible thunderstorms and tornadoes
Weather at a warm front
Clouds & precipitation; long periods of steady, light precipitation
Weather warning
Some sort of bad weather will happen
Weather watch
Weather conditions could happen