what factors affect our weather? heat in our atmosphere winds water cycle

What factors affect our weather?

• Heat in our atmosphere

• Winds

• Water cycle

Who predicts the weather?

• Meteorologists!– Scientists who study the causes weather & try

to predict it– They use a variety of methods to predict

weather...

What type of tools do they use?

• Barometer

• Anemometer

• Wind/Weather Vane

• Thermometer

What other tools do they use in forecasting our weather?

• Local weather observers

• Weather balloons

• Satellites

• Weather Stations

• Maps

• Charts

• Computers

• Radar

What is an air mass?

• Huge body of air that has similar temp, humidity, & air pressure

• Classified by temperature & humidity

Air Mass Types:

• Tropical

• Continental

• Maritime

• Polar

Tropical

• Warm air mass with low pressure that forming in the tropics

Continental

• Dry air mass over land

Maritime

• Humid air mass over an ocean

Polar

• Cold air mass with high pressure 50ºN/S latitude

What are the major types of air masses that affect the weather in

North America?

• Maritime Tropical

• Maritime Polar

• Continental Tropical

• Continental Polar

Maritime Tropical

• Form over Pacific-affects weather on the west coast

• Form over Gulf of Mexico or Atlantic-affects weather in the central & eastern US

Maritime Polar

• Form over North Atlantic-most are pushed out to sea by prevailing westerly winds

• Form over North Pacific-affects weather on west coast

Continental Tropical

• Form over Southwest & Mexico-brings dry, hot air to southwest & central US

Continental Polar

• Forms over central/northern Canada and Alaska

• Brings cold air to central & eastern US

How do these air masses move across the US?

• Prevailing westerlies

What is a front?

• The area where 2 air masses, with different temperatures & densities meet & do not mix

• A front may be 15-200km wide & extend 10km up into the troposphere

4 types of fronts:

• Cold

• Warm

• Stationary

• Occluded

Cold Front

• Rapidly moving cold air runs into slower moving warm air

• Cold air slides under the warm air

Warm Front

• Warm air runs into cold air

• Warm air moves over the cold air

Stationary Front

• Warm and cold air meet

• Neither has enough force to move the other

Occluded Front

• Warm air is caught between 2 cold air masses

• Most complex

• Warm air rises & the 2 cold air masses mix

What types of severe weather affect the US?

• Thunderstorms

• Tornadoes

• Hurricanes

• Tropical Storms

• Flooding

Thunderstorms

• Heavy rainstorm accompanied by thunder & lightning

• Form within cumulonimbus clouds or “thunderheads”

Which occurs first…the thunder or lightning?

Lightning

• A sudden spark or energy discharge between 2 nearby clouds

Thunder

• The sound of the explosion when lightning occurs

…so which happens first?

• Lightning!

• Light travels faster than sound

Tornadoes

• A rapid, whirling, funnel-shaped cloud that reaches down from a storm cloud & touches Earth’s surface

How do tornadoes form?

• They form in low, heavy cumulonimbus clouds in spring/early summer in late afternoon when the ground is warm

• May only last 15mins or less, but causes serious damage with winds up to 480km per hour

How is the damage measured?

• Fujita Scale

Where do most tornadoes occur in the US?

• Tornado Alley

• Great Plains area including: – Central Texas– Kansas– Central Oklahoma– Nebraska

What’s the difference between a tornado warning & a tornado

watch?• Tornado Warning:a tornado has been spotted in

the sky or on radar

• Tornado Watch: a tornado is

possible in your area

Waterspout

• Tornado that forms over a body of water

• The US has more tornadoes than any other country …over 800 a year!

How do hurricanes affect the US?

• A hurricane is a tropical storm with winds of 119km per hour & 600km across

Hurricane Facts

• Longest lasting storm at over a week

• Hurricane Season: June-November

• Hurricane in the Pacific is called a typhoon

• Hurricanes gain strength from warm humid air over the ocean

• Hurricanes are propelled by winds

How does a hurricane form?

• They begin over warm water as an area of low pressure or a tropical disturbance

• Disturbance grows in size & strength called a tropical storm

What is the eye of the hurricane?

• The calm, clear center of a hurricane

Hurricane Watch vs. a Warning!

• Hurricane Watch: hurricane conditions are possible

• Hurricane Warning: hurricane conditions are expected within 24hours

How do floods affect the people in the US?

• A flood occurs when so much water pours into a stream/river overflowing its banks, covering land on either side

• Floods can be the most violent type of storm to affect the US

What is a flash flood?

• Unexpected, violent flood occurring within hours/minutes of a storm

What causes a flash flood?

• Snow/Ice melt

• Heavy Thunderstorms

• Breaking Dam

• Hurricanes/tropical storms

What is climate?

• The Average year-after-year conditions of an area– Conditions: temp, precipitation, winds, clouds

5 climate regions:

• Classified according to temp & precipitation

1. Tropical rainy

2. Dry

3. Temperate marine

4. Temperate continental

5. Polar