Air Masses and Weather Fronts: Types and Characteristics | Homework and Review

1. BEFORE THE BELL RINGS • Please copy your homework into your assignment book

2. Warm-up • What is a weather front? • What are different types of weather fronts you have heard of? End

3. Thursday, January 12, 2017 • Warm-up (collecting these today) • Review Air Masses and Fronts • Review game • Homework: Midterm Exam Review due 1/17

4. Air Masses: A large body of air that has the same properties as the surface over which it forms (source region). Example An air mass that forms over water will have higher humidity than an air mass that forms over land.

5. Air Masses: • Air Masses come from latitudes of high pressure (30 and 90) due to sinking air hitting the ground and spreading out. • Air mass Weather is CONSTANT! • The leading edge of an air mass (FRONT) causes our day to day weather change.

6. Air Mass Identification • Air masses are named for the region over which they form. (Source Region) Moisture content and Temperature! • Identification: Cold = Polar Warm = Tropical Dry = Continental Humid = Maritime

7. Types of Air Masses • There are five (5) types of air masses: 1. Continental Arctic (cA) 2. Continental polar (cP) 3. Maritime polar (mP) 4. Maritime tropical (mT) 5. Continental Tropical (cT)

8. Continental Arctic (cA): 1. Extremely cold temperatures and very little moisture. 2. These usually originate north of the Arctic Circle. 3. cA air masses affect Canada and occasionally the USA during winter.

10. Continental polar (cP): 1. Cold and dry, but not as cold as Arctic air masses. 2. These form south of the Arctic circle and often dominate the weather picture across the North central and Eastern U.S. during winter. 3. cP masses do form during the summer, but usually influence only the northern USA. 4. These air masses are responsible for bringing clear and pleasant weather during the summer to the North.

12. Maritime polar (mP): 1. Cool and humid. 2. mP air masses form over the northern Atlantic and the northern Pacific oceans. 3. They most often influence the Pacific Northwest and the New England States. . 4. mP air masses can form any time of the year and are not as cold as cP air masses.

14. Maritime tropical (mT): 1. Warm and humid! 2. mT air masses are most common across the eastern and central U.S. and originate over the warm waters of the Southern Atlantic and the Gulf of Mexico. 3.These air masses can form year round, but they are most prevalent across the U.S. during summer. 4. Maritime tropical air masses are responsible for the hot, humid days of summer.

16. Continental Tropical (cT): 1. Hot and very dry. 2. cT usually form over the Desert Southwest and northern Mexico during summer. 3. cT can bring record heat to the Plains and the Mississippi Valley during summer, but they usually do not make it to the East and the Southeast during winter.

18. WEATHER FRONTS Chapter 12 notes

20. FRONTS • Front: • A boundary separating any contrasting air masses (cold air mass/warm air mass). • The leading edge of an air mass! • The warm air mass is always pushed up by the cooler air mass. (FRONTAL LIFTING!!!) • Due to warm moist air being pushed up, storms and precipitation often occur at front.

21. Severity of Weather • The more intense the Frontal Lifting (Updrafts): • The lower the pressure • The more severe weather conditions • Depends on Diversity of Air Masses and Speed of Air Mass movement.

22. FRONTS • Four (4) Types of Fronts 1. Cold Front 2. Warm Front 3. Stationary Front 4. Occluded Front

23. COLD FRONT • On a weather map, a cold front is always represented by a line with blue triangles • The arrows tell where the warm air is and the direction the front is moving

24. Cold air COLD FRONT • A cold front forms when a cold air mass moves into an area that was covered by a warm air mass.

25. COLD FRONT

26. COLD FRONT CONDITIONS • Altocumulus clouds are often seen ahead of a cold front. • Cumulonimbus clouds may be found along the front. • Cold fronts usually bring high winds, heavy rains, and possible violent weather but only for a short period of time.

27. COLD FRONT CONDITIONS • After the front passes, skies will begin to clear. • Winds will shift from the South to the West/Northwest after the front passes. • http://www.phschool.com/atschool/phsciexp/active_art/weather_fronts/

29. WARM FRONT • On a weather map, a warm front is always represented by a line with red semi-circles. • The semi-circles tell where the cold air is and the direction the front is moving

30. Warm air WARM FRONT • A warm front forms when a warm air mass moves into an area that was covered by a cold air mass.

31. WARM FRONT

32. WARM FRONT CONDITIONS • The first sign that a warm front is approaching is the appearance of cirrus clouds. • As the front moves closer, cirrostratus clouds move in followed by altostratus, and finally, thick stratus or nimbostratus clouds fill the sky. • Warm fronts usually bring light to moderate rain over a large area for several days.

33. WARM FRONT CONDITIONS • After the front passes, skies will generally clear although some cumulus or altocumulus clouds are present. • Winds will shift from the South to West after the front passes.

35. STATIONARY FRONT • On a weather map, a stationary front is always represented by a line with red semi-circles on one side and blue triangles on the other.

36. STATIONARY FRONT • Stationary fronts are formed when pressure differences cause the front to stop moving. • The condition may last for several days. • Weather at a stationary front will be overcast with light wind and light precipitation.

38. OCCLUDED FRONT • On a weather map, an occluded front is always represented by a line with semi-circles and triangles on the same side colored purple

39. OCCLUDED FRONT • Occluded fronts are formed when 2 cold air masses come together and force warm air up between them. • The weather at an occluded front is very complex and difficult to predict. However, strong winds and heavy rains often accompany this type of front.

40. OCCLUDED FRONT

41. EARTH SCIENCEGeology, the Environment and the Universe Chapter 13: The Nature of Storms

42. SECTION13.1 Thunderstorms Essential Questions • How do thunderstorms form? • What are the different types of thunderstorms? • What is the life cycle of a thunderstorm? Review Vocabulary • latent heat: stored energy in water vapor that is not released to warm the atmosphere until condensation occurs

43. SECTION13.1 Thunderstorms • The intensity and duration of thunderstorms depend on the local conditions that create them. New Vocabulary air-mass thunderstorm mountain thunderstorm sea-breeze thunderstorm frontal thunderstorm stepped leader return stroke

44. SECTION13.1 Thunderstorms Up to 2000 thunderstorms are in progress around the world

45. SECTION13.1 Thunderstorms • Both geography and air mass movements make thunderstorms most common in the southeastern United States.

46. SECTION13.1 Thunderstorms How thunderstorms form • For a thunderstorm to form, three conditions must exist: a source of moisture, lifting of the air mass, and an unstable atmosphere.

47. SECTION13.1 Thunderstorms Limits to thunderstorm growth TROPOPAUSE

48. SECTION13.1 Thunderstorms Types of Thunderstorms • Thunderstorms are often classified according to the mechanism that causes the air mass that formed them to rise. • There are two main types of thunderstorms: air-mass and frontal.

50. SECTION13.1 Thunderstorms Types of Thunderstorms Air-mass thunderstorms • When air rises because of unequal heating of Earth’s surface beneath one air mass, the thunderstorm is called an air-mass thunderstorm. • There are two kinds of air-mass thunderstorms.