Weather What causes weather patterns? - PowerPoint Presentation

Slide1

WeatherSlide2

What causes weather patterns?

The

sun! The

sun

is the source of almost all heat and energy. The sun heats air, which causes it to become less dense and rise and change temperature. Remember… the tilt of the Earth in relation to the sun causes the seasons. Slide3

Weather is the

atmospheric conditions present in an area.

Weather

is the day-to-day conditions of the air in a

particular place. The components of weather include: temperature, precipitation, wind, sunshine, visibility, air pressure, clouds, and location of the area.Slide4

Climate

Climate is the pattern of weather in an area over a period of many

years

.Slide5
Slide6

Weather vs. Climate

Weather

A

short

period of time

Short term changes in the

atmosphere

Colorado

Weather: Today it is sunny with a chance of

rain

. The temperature is 62 degrees.

Climate

Long period of

time

Long term weather

pattern

of a particular area

A

PATTERN of weather

Colorado (Fort Collins) Climate:

dry

winters with some snow,

windy

springs, low humidity winters, pleasant falls. Semi-arid. Highly changeable

weather

.Slide7

CloudsSlide8

What are clouds made of?

Clouds - are made of tiny water

droplets that condense from water vapor in rising air

.Slide9

Different characteristics

Clouds have different characteristics because they form under

different

conditions and at different

altitudes. Some cloud types and characteristics include:Slide10

Cirrus Clouds

wispy because they form in cold air at very high altitudes and are made of

ice

crystals

fair weather can be signs of a storm comingSlide11

Cumulus Clouds

puffy

with flat bottom can have darker bases

Usually in the

daytime in fair weatherIf cumulus clouds keep growing taller, they can produce showers which changes the name to cumulonimbus clouds. Slide12

Stratus Clouds

Smooth/Layers because they form

without

strong air

movement. Usually make the whole sky appear to be grayLow stratus clouds can be so dark that they completely block out the sunCan produce steady, light precipitationSlide13

Cloud Prefixes or Sufixes

Cumulas

= heaped or puffy

Stratus = layers

Cirros = high (above 20,000ft.)Alto = middle (between 70,000ft. -20,000ft.)Nimbo/Nimbus = PrecipitationVirga = rain that falls from a cloud and does not hit the groundSlide14
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Air Masses and Fronts

An air mass's

temperature

and

humidity depend on the characteristics of the land or water over which it forms. Air masses move and push each other. An air mass can be: continental (dry) or maritime (moist), and polar (cold) or tropical (warm)Fronts form where air masses meet. Slide17
Slide18

Cold Front

When the colder air mass pushes

the warmer air mass, a steep cold front occurs. There may be

thunderstorms

along the front.Symbol: solid line with triangles along the front pointing towards the warmer air Slide19

Warm Front

When the warmer air pushes

the colder air, a warm front occurs. There may be

overcast

skies and steady precipitation.Symbol: solid line with semicircles pointing towards the colder air.Slide20

Stationary Front

When the boundary is not

moving, it is called a stationary front.

Symbol

has both the cold front (triangle) and the warm front (semicircle) symbols. Slide21

Occluded Front

Front

forms as the cold air

behind

the cold front meets the cold air ahead of the warm front. Symbol: solid purple line with alternating triangles and semi-circles. Slide22

Two types of pressure systems

High-pressure systems = weather that form around a high-pressure center.

Fair

weather usually results

.Low-pressure systems often form where air masses meet. Rising air at the fronts and at the low can cause stormy weather.Slide23
Slide24

A thunderstorm is a storm with lightning

and thunder. It’s

produced by a cumulonimbus cloud, usually producing

gusty

winds, heavy rain and sometimes hail.Slide25

The basic ingredients used to make a thunderstorm are

moisture, unstable air and lift

.

You

need moisture to form clouds and rain. You need unstable air that is relatively warm and can rise rapidly. Finally, you need lift. This can form from fronts, sea breezes or mountains.Slide26

Thunderstorms can

occur

year-round and at all hours. But they are most likely to happen in the

spring

and summer months and during the afternoon and evening hours.Slide27

It is estimated that there are around 1,800

thunderstorms that occur across our planet every day.Slide28

All thunderstorms are dangerous

. Every thunderstorm produces lightning, which kills more people each year than tornadoes

.Slide29
Slide30

Tornadoes

A

tornado is a violent rotating column of air extending from a

thunderstorm

to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of up to 300 mph. Slide31

Most tornadoes form from

thunderstorms. You need warm, moist air from the Gulf of Mexico and cool, dry air from

Canada

. Slide32

When these two air masses meet, they create instability in the

atmosphere

. A change in wind

direction

and an increase in wind speed with increasing height create an invisible, horizontal spinning effect in the lower atmosphere. Rising air within the updraft tilts the rotating air from horizontal to vertical. An area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.Slide33

When do they happen?

Tornadoes can happen at any time of the

year

and at any time of the

day. In the southern states, peak tornado season is from March through May. Peak times for tornadoes in the northern states are during the summer. A few southern states have a second peak time for tornado outbreaks in the fall. Tornadoes are most likely to occur between 3 p.m. and 9 p.m. Slide34

The geography of the Great Plains, located in the

central United States, is suited to bring all of the ingredients

together to form

tornadoes.

The Great Plains are also known as Tornado Alley. More than 500 tornadoes typically occur in this area every year. Texas, Oklahoma, Kansas, Nebraska, South Dakota, North Dakota, Iowa, Missouri, Arkansas and Louisiana all make up Tornado Alley.Slide35
Slide36

A hurricane is a

huge storm! It can be up to 600 miles across and have strong winds spiraling inward and upward at speeds of 75 to 200

mph.

Each

hurricane usually lasts for over a week, moving 10-20 miles per hour over the open ocean. Slide37

Hurricanes gather

heat and energy through contact with

warm

ocean waters.

Evaporation from the seawater increases their power.Hurricanes rotate in a counter-clockwise direction around an "eye" in the Northern Hemisphere and clockwise direction in the Southern Hemisphere.The center of the storm or "eye" is the calmest part. It has only light winds and fair weather. When they come onto land, the heavy rain, strong winds and large waves can damage buildings, trees and cars.Slide38

Hurricanes only form over really

warm ocean water of 80°F or warmer. The atmosphere (the air) must cool off very

quickly

the higher you go. Also, the wind must be blowing in the same

direction and at the same speed to force air upward from the ocean surface. Winds flow outward above the storm allowing the air below to rise. Hurricanes typically form between 5 to 15 degrees latitude north and south of the equator. The Coriolis Effect is needed to create the spin in the hurricane and it becomes too weak near the equator, so hurricanes can never form there. Slide39
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What is a storm surge?

Storm surges are frequently the most

devastating

element of a hurricane. Slide42

What is a storm surge?

As a hurricane’s winds

spiral

around and around the storm, they push

water into a mound at the storm’s center. This mound of water becomes dangerous when the storm reaches land because it causes flooding along the coast. The water piles up, unable to escape anywhere but on land as the storm carries it landward. A hurricane will cause more storm surge in areas where the ocean floor slopes gradually. This causes major flooding.Slide43
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Hurricane Seasons

The Atlantic hurricane season is from June 1 to November 30, but most hurricanes occur during the

fall

months.

The Eastern Pacific hurricane season is from May 15 to November 30.Slide45

Who names hurricanes? (This is just for fun, you won’t be tested over the naming of hurricanes.)

From

1950 to 1952, tropical cyclones of the North Atlantic Ocean were identified by the phonetic alphabet (Able-Baker-Charlie-etc.), but in 1953 the US Weather Bureau switched to women's names.

T

he rest of the world eventually caught on, and naming rights now go by the World Meteorological Organization, which uses different sets of names depending on the part of the world the storm is in. Around the U.S., only women's names were used until 1979, when it was decided that they should alternate a list that included men's names too. There's 6 different name lists that alternate each year. If a hurricane does significant damage, its name is retired and replaced with another.