Air Masses and Fronts CHAPTER 17 1 FRONTS

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 u A cold air mass replaces a warm air mass • Showers and Thunderstorms are common • Cooler and drier air follows the front

WARM FRONT u 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 u 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 u 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

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 1) 2) 3) 4) 5) 6) 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 u u u u 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? _____________.