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