Air Masses and Fronts CHAPTER 17-1
FRONTS A FRONT is the boundary between two different air masses • Storms and changeable weather are common • Differences in air pressure, temperature and humidity are common with fronts • Four types of fronts are: • Cold • Warm • Stationary • Occluded
COLD FRONT • A cold air mass replaces a warm air mass • Showers and Thunderstorms are common • Cooler and drier air follows the front
WARM FRONT • A warm air mass replaces a cold air mass • Steady precipitation for several hours or days • Weather tends to be warm and humid
STATIONARY FRONT • A front that does not move or barely moves • Two air masses in a “standoff” with neither one moving • Periods of rain, drizzle and fog are common • Several days of clouds and precipitation are likely • Temperatures remain constant and winds are gentle
OCCLUDED FRONT • Occurs when a warm air mass is caught between two cooler air masses • Warm air is “cut off” from the ground • Periods of rain or snow are common warm warm
ANTICYCLONES High pressure centers of dry air • Usually called “HIGHS” • Appears as an “H” on a weather map • Winds spin clockwise in N. Hemisphere • Areas of sinking air in the center • Dry, clear weather is likely
ANTICYCLONES HIGH PRESSURE AREAS
CYCLONES Low pressure areas • Usually called “LOWS” • Appears as an “L” on a weather map • Winds spin counterclockwise in N. Hemisphere • Areas of warm, rising air in the center • Clouds and precipitation are likely
CYCLONES LOW PRESSURE AREAS
REVIEW # 1 1) The air mass that forms over central Canada is called_________ 2) The front that brings rising temperatures and steady rain is the ______front 3) The air mass that is warm and humid is called__________ 4) The front that brings showers and cooler temperatures is called a ______front 5) The front that doesn’t move is called_______ 6) An air mass that is warm and dry is called ? 7) Clear and dry weather is common to a _____
REVIEW # 2 • What are the symbols used on a weather map for the four types of fronts? • In what direction do LOWS spin? • How many air masses are found in an OCCLUDED FRONT? • What are the weather conditions does a CYCLONE bring? • Air masses move across the U. S. from ________ to __________. • What kind of air mass is outside today?
REVIEW # 3 • 1) Maritime means ________________. • 2) Tropical means________________. • 3) Continental means_______________. • 4) Polar means________________. • 5) Several days of clouds and precipitation would be likely with a _________ front. • 6) Which air mass forms over the Gulf of Mexico? ______ • 7) An “L” on a weather map is called ___.
REVIEW ANTICYCLONE 1) What direction does it spin in the northern hemisphere? ______________ 2) What kind of weather does it have? ________ ___________. 3) What is another name for this feature?_______ _____________.
REVIEW CYCLONE 1) What direction does it spin in the northern hemisphere? ___________________. 2) What kind of weather does it have?_________ ______________. 3) What is another name for this feature?_______ __________________.