2. What factors affect our weather? Heat in our atmosphere Winds Water cycle

3. Who predicts the weather? Meteorologists! –Scientists who study the causes weather & try to predict it –They use a variety of methods to predict weather...

4. What type of tools do they use? Barometer Anemometer Wind/Weather Vane Thermometer

5. What other tools do they use in forecasting our weather? Local weather observers Weather balloons Satellites Weather Stations Maps Charts Computers Radar

6. What is an air mass? Huge body of air that has similar temp, humidity, & air pressure Classified by temperature & humidity

7. Air Mass Types: Tropical Continental Maritime Polar

8. Tropical Warm air mass with low pressure that forming in the tropics

9. Continental Dry air mass over land

10. Maritime Humid air mass over an ocean

11. Polar Cold air mass with high pressure 50ºN/S latitude

12. What are the major types of air masses that affect the weather in North America? Maritime Tropical Maritime Polar Continental Tropical Continental Polar

13. 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

14. 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

15. Continental Tropical Form over Southwest & Mexico-brings dry, hot air to southwest & central US

16. Continental Polar Forms over central/northern Canada and Alaska Brings cold air to central & eastern US

17. How do these air masses move across the US? Prevailing westerlies

18. 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

19. 4 types of fronts: Cold Warm Stationary Occluded

20. Cold Front Rapidly moving cold air runs into slower moving warm air Cold air slides under the warm air

21. Warm Front Warm air runs into cold air Warm air moves over the cold air

22. Stationary Front Warm and cold air meet Neither has enough force to move the other

23. Occluded Front Warm air is caught between 2 cold air masses Most complex Warm air rises & the 2 cold air masses mix

24. What types of severe weather affect the US? Thunderstorms Tornadoes Hurricanes Tropical Storms Flooding

25. Thunderstorms Heavy rainstorm accompanied by thunder & lightning Form within cumulonimbus clouds or “thunderheads”

26. Which occurs first…the thunder or lightning?

27. Lightning A sudden spark or energy discharge between 2 nearby clouds

28. Thunder The sound of the explosion when lightning occurs

29. …so which happens first? Lightning! Light travels faster than sound

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

31. How do tornadoes form? They form in low, heavy cumulonimbus clouds in spring/early summer in late afternoon when the ground is warm

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

33. How is the damage measured? Fujita Scale

35. Where do most tornadoes occur in the US? Tornado Alley Great Plains area including: –Central Texas –Kansas –Central Oklahoma –Nebraska

36. 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

37. Waterspout Tornado that forms over a body of water

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

39. How do hurricanes affect the US? A hurricane is a tropical storm with winds of 119km per hour & 600km across

40. 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

42. 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

44. What is the eye of the hurricane? The calm, clear center of a hurricane

45. Hurricane Watch vs. a Warning! Hurricane Watch: hurricane conditions are possible Hurricane Warning: hurricane conditions are expected within 24hours

46. 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

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

48. What is a flash flood? Unexpected, violent flood occurring within hours/minutes of a storm

49. What causes a flash flood? Snow/Ice melt Heavy Thunderstorms Breaking Dam Hurricanes/tropical storms

50. What is climate? The Average year-after-year conditions of an area –Conditions: temp, precipitation, winds, clouds

52. 5 climate regions: Classified according to temp & precipitation 1.Tropical rainy 2.Dry 3.Temperate marine 4.Temperate continental 5.Polar