20-1 Flashcards
what are severe storms? what storms happen in spring and summer vs late summer and early fall?
one of nature’s most destructive forces. Spring and summer - tornadoes, force is strong; late summer and early fall - hurricanes over tropical oceans; destruction
what are summer heat waves?
several days of high temperatures and humidity that causes series of storms through an area; stormy weather followed by cool weather
what are winter cold spells?
periods of frigid temperatures under clear skies; bitter cold periods followed by cloudy, snowy, warm days that are milder
what are periods of fairly constant weather conditions followed by?
short period of changes in the weather
what are air masses?
extremely large body of air in the troposphere with similar temperatures and amounts of moisture at any given altitude; takes several days to move over an area
what is the weather at air masses?
fairly constant weather
What happens when an air mass moves out of the region where it formed?
It carries its temperature and moisture conditions with it. As it travels, its characteristics change, affecting the weather in the areas it moves over.
what is a source region?
area over an air mass gets characteristic properties of temperature and moisture
describe polar (P) air masses
high altitudes, near poles, cold
describe tropical (T) air masses.
low latitudes, near equator, warm
describe continental (c) air masses.
form over land, dryer
describe maritime (m) air masses.
form over water, humid
what are the four basic types of air masses that utilize classification scheme?
continental polar (cP), continental tropical (cT), maritime polar (mP), and maritime tropical (mT)
describe cP air masses
dry cold air, As they travel south their relative humidity lowers, results in sunshine
what is lake-effect snow? how does it relate to the cP air mass?
cold dry air flowing over lake picks up lots of heat and moisture, making it rise, hit cool air, and cool to dew point. cP air mass is traveling south and east because of prevailing westerlies so south and east side of the lake receives snow
what are snow belts?
areas where you receive lots of snow from lake-effect snow
describe cT air masses. what happens when it moves outside source regions?
dry warm air, begins in southwestern USA and Mexico in the summer, usually does not move outside source regions, but when it does it brings extreme heat and drought to Great plains
what is an Indian summer?
Movement of cT air masses in the fall resulting in mild weather
describe mP air masses (where it moves from and to, how it starts and becomes)
Cold and humid air moves from the Pacific to the Northwest USA, starting as cP and becoming milder, wetter, and more unstable over the ocean.
How does mP air affect weather in the Northwest USA and New England? how does a nor’easter form?
In the Northwest, mP air causes clouds and showers in WA and OR, with heavy rain or snow in the Cascades. In winter, New England can get heavy snow or rain when low pressure pulls in ocean moisture, creating a nor’easter.
describe mT air masses. (what it brings in summer, in USA)
humid, warm, unstable air, major source of precipitation in eastern ⅔ of USA, in summer it brings warm and humidity to our area, typical at its source region (tropics)
