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Weather/ Comic notes
Clouds
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A collection of small water droplets or ice crystals suspended in the air, which forms when
the air is cooled and condensation occurs
Three kinds of clouds
o Cumulus clouds
 Puffy white clouds
 Flat bottoms
 Warm air rises, form
 Fair weather
 Cloud gets larger= thunderstorm, cumulonimbus cloud
o Stratus clouds
 Clouds that form in layers
 Large areas of the sky
 Block out the sun
 Nimbostratus clouds= rain and fog
o Cirrus clouds
 Thin, feathery, white clouds
 High altitudes
 Made of ice crystals
 Wind is strong
 Change in weather
Classified by altitude
High altitude= ice crystals; prefix= cirro
Middle altitude= water drops, ice crystals; prefix= alto
Low clouds= water drops
Precipitation
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Any form of water that falls to the Earth’s surface from the clouds
Can be sold or liquid, four major forms
o Rain
 Common form
 Water drops in cloud become large enough to fall
 Droplet smaller than the period
o Sleet
 When rain falls through a layer of freezing air
 Falling ice
o Snow
 Temperatures are so cold that water vapour changes directly to a solid
 Single ice crystals or snowflakes
o Hail
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Balls or lumps of ice that forms from clouds
Forms in cumulonimbus clouds
Updrafts of air in the clouds carry raindrops high in the clouds, the raindrop
freeze
Hail falls, water drop coats it
Updrafts of air can send the hail up again
Water drops collected on the hail freeze to form another layer of the ice
Air Mass
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Change in weather caused by movements and interaction of air masses
Air mass= a large body of air where temperature and moisture content are constant
throughout
Moisture content and temperature are determined by the area over which the air mass
forms; area= source regions
Two kinds
o Cold air masses
 Three polar air masses
 Continental polar (cP)
o A cP air mass generally brings cool, dry weather
 Maritime polar (mP)
o Cool and very wet
o Rain and snow in winter
o Cool and fog in summer
o Warm air masses
 Four warm air masses
 Maritime tropical (mT)
o Over warm areas, milder than mP
o Summer= hot and humid weather, hurricanes and
thunderstorms
o Winter= mild, often cloudy weather
 Continental tropical (cT)
o Summer= clear, dry and hot weather
Fronts
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The boundary between air masses of different densities and usually different temperatures
Air masses, form from different area, don’t mix= different densities
Warm air is less dense than cold air
Two types of air masses meet, warm air rises
Associated with weather and middle latitudes
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4 kinds of fronts
o Cold front
 Forms when cold air moves under warm air, which is less dense, and pushes
the warm air up
 Move quickly, bring thunderstorms, heavy rain, snow, cooler weather
o Warm front
 Forms when warm air moves over cold, denser air
 Warm air replaces cold air
 Drizzly rain, clear and warm weather
o Occluded font
 Forms when warm air mass is caught between two cold masses
 Coldest air moves under and pushes up the warm air mass
 Coldest air moves forward, meets cold air mass warm and less dense
 Colder of the two air moves under and pushes warm air mass
 Two colder air masses may mix
 Cool temperatures, large amounts of rain and snow
o Stationary font
 Cold air mass meets warm air mass
 Do not have enough force to lift the warm air mass over cold air mass=
separated= not enough wind
 Many days of cold, cloudy, wet weather
Cyclones and anticyclones
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Low pressure and high pressure
Cyclones
o An area in the atmosphere that has lower pressure than the surrounding areas and
has winds that spiral toward the centre
o Air masses come together, or converge, and rise
o Air in the centre of the cyclone rises, cools and forms cloud and rain
o Causes stormy weather
Anticyclones
o The rotation of air around a high-pressure centre in the direction opposite to Earth’s
rotation
o Area where air moves apart, or diverges, and sinks
o Sinking air is denser than surrounding air, and the pressure is higher
o Cooler, denser air moves out of the centre of these high-pressure areas toward
areas of lower-pressure
o Air sinks, gets warmer and absorbs moisture
o Brings dry, clear weather
Keep track of cyclones and anticyclones can predict the weather
Thunderstorm
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Severe weather is weather that can cause property damage and sometimes death
A usually brief, heavy storm that consists of rain, strong winds, lightning and thunder
Loud and powerful
Two atmospheric conditions= warm and moist air near Earth’s surface and unstable
atmosphere
Unstable when surrounding air is colder than the rising air mass
Rising warm air reaches its dew point, the water vapour in the air condenses and forms
cumulus clouds
Lightning= an electric discharge that takes place between two oppositely charged surfaces,
such as between a cloud and the ground, between two clouds, or between two parts of the
same cloud
o Ex. Friction between the floor and your shoes builds up an electric charge in your
body
o Lightning strikes, energy is released
o Happens in all thunderstorm
o Very powerful= start thousands of forest fires, killing and injuring people
Thunder= the sound caused by the rapid expansion of air along an electric strike
Causes high winds, hail, flash floods, tornadoes
Hailstorm= damage crops, dent metal on cars, break windows
Flash flooding= heavy rain, millions of dollars in property damage, weather-related deaths
Turn on radio and tv during a storm
Stay away from trees, crouch down, stay away from bodies of water
Tornadoes
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A destructive, rotating column of air that has very high wind speeds, is visible as a funnelshaped cloud, and touches the ground
1% of all thunderstorms
Wind moving in two directions causes a layer of air in the middle to begin to spin
Spinning column of air is turned to a vertical position by strong updraughts of air in the
cumulonimbus cloud. Updraughts of air begin to spin.
Spinning column of air moves to the bottom of the cumulonimbus cloud and forms a funnel
cloud
Funnel clouds become a tornado when it touch the ground
75% of worlds tornado= united states
Spring and early summer when cold, dry air from Canada meets warm, moist air from the
tropics
Ability to cause damage= strong spinning winds
Uproot trees, destroy buildings
Capable of picking up heavy objects such as mobile homes and cars, hurling them through
air
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Watches and warnings
Watch= weather alert that let people know that a tornado may happen
Warning= weather alert that lets people know tornado has been spotted
Shelter= basement or cellar; windowless rooms= bathroom, closet, or hallway; lie down in a
large, open field or a deep ditch
Hurricanes
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A severe storm that develops over tropical oceans and whose strong winds of more than 120
km/h spiral in toward the intensely low-pressure storm centre
Powerful storms
Also known as Typhoons and cyclones
Form in the areas between 5 degree and 20 degree north latitude and between 5 degree
and 20 degree south latitude over warm, tropical oceans
Begin as a group of thunderstorm moving over tropical ocean water
Wind travelling in two different directions meet and cause the storm to spin
Coriolis effect= storm turn counter clockwise in northern hemisphere and clockwise in
southern hemisphere
Warm, moist air rises, the water vapour condenses, releases large amount of energy
Hurricanes move into colder waters or over land, begins to die, lost source of energy
Surround the eye= eye wall= a group of cumulonimbus clouds that produce heavy rains and
strong winds= strongest part of hurricanes
Centre of hurricane= eye= a core of warm, relatively calm air with low pressure and light
winds
Beyond the eye wall, spiralling bands of clouds called rain bands circle the centre of the
hurricane= heavy rains and high winds
Knock down trees and telephone poles, damage and destroy buildings and homes
Caused by flooding associated with heavy rains and storm surges
Storm surges= wall of water that builds up over the ocean because of the strong winds and
low atmospheric pressure
Flooding= tremendous danger to property and lives
TV or radio station, evacuate the area, disaster supply kit that includes enough water and
food that lasts for several days, protect windows (cover with plywood), must stay indoors