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

FRONT SYMBOLS

WEATHER MAP SYMBOLS

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?_______ __________________.