Weather Vocabulary
Name: ____KEY______________________ Date: _______________ Class: _____________
Humidity
A measure of the amount of water vapor in the air; warm air holds more water vapor than cold air
Relative
Humidity
The % of water vapor that’s actually in the air compared to the maximum amount that the air can hold at a particular temp.; 100% relative humidity means the air is saturated
w/water
Dew
Point
The temperature at which condensation begins to form; if dew point is above freezing water droplets form; if its below freezing ice crystals may form
Cirrus
Clouds
Wispy, feathery clouds, form at high altitudes (6 kilometers high)where temps are low, made of ice crystals
Means “curls of hair”
Cumulus
Clouds
Fluffy, rounded piles of cotton, form less than 2 km above the ground, but may grow in size & height until they extend 18 km
, sometime called “fair weather cumulus” when seen on sunny days, when they grow high & dark they are called
cumulonimbus & predict thunderstorms (nimbus means “rain”)
Means “heap” or “mass”
Flat, spread out layers, may cover the whole sky, uniform dull, gray color, may bring drizzle, rain or snow (called
nimbostratus)
Means “spread out”
Stratus
Clouds
Air
Mass
Huge body of air that has similar temp, humidity & air pressure at any height; may spread over millions of square km & be up to 10 km deep; characterized by humidity & temp –
4 main types of air masses…
In the U.S. air masses are moved by prevailing westerlies & jet streams
Tropical
Air Mass
Polar
Air Mass
Maritime
Air Mass
Warm air masses form in the tropics & have low air pressure
Continental
Air Mass
Air masses form over land, drier; Continental Polar air masses form over Canada & Alaska & bring bitterly cold, drier weather
Front
The boundary where two air masses meet; storms form & weather changes along fronts; air masses don’t mix easily
Cold air masses form north of 50° north latitude & 50° south latitude, have high air pressure
Air masses that form over oceans, very humid; Maritime Tropical air masses form over Gulf of Mexico & Atlantic Ocean & move into southeastern U.S. – bring hot, humid
weather in the summer with thunderstorms & showers and in the winter they bring snow or heavy rain
Fast-moving, dense air sinks under slow-moving warm fronts, warm air rises forming clouds
Cold Front
May cause sudden thunderstorms,
followed by colder, drier air with clear
skies
May cause several days of rain or
clouds then warm & humid days will
follow
May bring days of clouds & precipitation
(rain, snow, sleet , fog or clouds)
cold air moves in & warm air
rises
Warm air moves over
Warm Front
Fast-moving warm air mass overtakes a slow-moving cold air mass, warm air moves over the
cold, dense air; Warm, dry air = scattered clouds
Stationary
Front
Cold & warm air masses meet in a “standoff” – neither can move the other, stalls over the area
Occluded
Front
Warm air mass is caught & trapped between 2 cold air masses, temp near ground is cold due to
the cold air masses staying low while warm air cools & condenses – forming clouds
Cyclone
A swirling center of low pressure , as warm air rises at the center air pressure decreases, cooler air blows in ; cyclones play a large role in the weather of U.S. – associated
with clouds, wind & precipitation
“LOWS” = L on weather maps
Anticyclone
Storm
High pressure center of dry air, cool air moves downward from high in the troposphere, as it falls, it warms up so its relative humidity drops – associated with dry. clear
weather
“HIGHS” = H on weather maps
Violent disturbance in the atmosphere, involve sudden changes in air pressure which causes rapid air movements
Lightning &
Thunder
Lightning is a sudden spark of electrical discharge that has built up in storm clouds; Thunder is the sound of the explosion as the heated air suddenly expands in lightning
Thunder ALWAYS follows Lightning (Lightning McQueen – ‘Cars’ movie!)
dense cold air
cold & warm meet
neither moves
May cause cloudy days with rain or
snow falling
Storm surge
A “dome” of water that sweeps across the coast where a hurricane lands, raises water level up to 6 meters above normal sea level; causes great damage, washes away
beaches, destroys buildings & erodes coastlines,
Type of Storm What is it?
How does it form?
How to be safe:
Thunderstorm Small storms with heavy precipitation & frequent thunder &
Cumulonimbus Clouds form on hot, humid afternoons or when warm air Stay indoors, avoid water &
lightning
is forced upward along a cold front – warm humid air rises rapidly, the metal objects or appliances that
air cools forming thunderheads (When? Spring /Summer)
conduct electricity
Tornado
Rapidly whirling, funnel-shaped cloud that reaches from storm
cloud to the ground
Snowstorm
Heavy snowfalls that block roads, trap people in cars/homes,
blowing winds disorient people
Hurricane
Tropical cyclone with winds of 119 km/hour or higher, may be
600 km across; Hurricanes form in the Atlantic, Pacific &
Form from similar clouds that bring thunderstorms, occur in summer
& spring mostly ( in Tornado Alley warm, moist air from Gulf of Mexico
meets cold, dry air from Canada forming a squall line which may
produce 10 or more tornadoes in 1 squall – 800 occur in Tornado Alley
every year)
Extreme cold, air colder than 0°C all the way to the ground
Move to basement or sturdy area
w/out windows or doors
Begins over warm ocean water as a low pressure area or tropical
disturbance which grows to a tropical storm, then to a hurricane; lasts
Evacuate (leave) the area
immediately
Find shelter from wind, cover
exposed areas of skin, stay dry
Indian Oceans; Typhoons form in the western Pacific Ocean;
eye is calm.
a week or more; loses strength as it passes over land since it no longer
has warm, moist air to draw from (When? Late summer-fall)
5 Types of Precipitation
(depend on temps)
Hail
Rain
At least 0.5 mm in
diameter
Drizzle & mist
(small drops of
water) fall from
stratus clouds
Temp > freezing
Round pellets
larger than 0.5 mm
Forms inside
cumulonimbus
clouds during
thunderstorms as
pellets are tossed
around in the
clouds, they fall to
the ground when
they get too heavy
Sleet
Snow
Water vapor in a
cloud that is made
directly into ice
crystals called
snowflakes
Powdery snow
forms when snow
falls through cold,
dry air; it clumps
together as it falls
through humid air
close to freezing
Ice particles
smaller than 5mm
Freezing Rain
Raindrops that fall
through air that is
below 0°Celsius
(the freezing point
of water) freeze
into solid particles
of ice
Raindrops falling
through cold air
near the ground
that don’t freeze in
the air – they
freeze on cold
surfaces
You can hear it
hitting surfaces.
Georgia in the
winter!