BJU Earth Science Chapter 20

air mass

A huge body of air in the troposphere with similar temperature and humidity throughout

continental air mass

A low humidity air mass that originates over land

maritime air mass

A high humidity air mass that originates over oceans

arctic air mass

A frigid air mass that originates over the poles

polar air mass

A cool or cold air mass that originates over upper latitudes

tropical air mass

A warm air mass that originates in the tropics

front

The boundary where at least two different air masses meet

orographic lifting

The upward movement of air masses as they flow over mountains

frontal wedging

The lifting of a warm air mass above a cool air mass acting as a wedge

convergence

The lifting of air when horizontal air currents from opposite directions collide and rise into the atmosphere

storm

A severe weather disturbance involving high winds, heavy precipitation, and other conditions, such as lightening or low temperatures

winter storm

A storm that brings heavy snow or sleet, high winds, and/or unusually cold weather

thunderstorm

A rainstorm that produces lightening. It may include hail, bursts of strong winds, and even tornadoes

lightning

An atmospheric electrical discharge that occurs either between clouds or between a cloud and the ground

tornado

A destructive, localized, rapidly rotating cyclonic windstorm forming a funnel; usually associated with a special cumulonimbus cloud called a supercell

hurricane

An immense cyclonic windstorm that forms over tropical or subtropical oceans; hazardous to ships at sea and extremely damaging if it moves over land; also called a typhoon or cyclone

tropical storm

A strong cyclonic storm with winds of at least 63 km/h (39mi/h). They can strengthen into hurricanes.

eye (hurricane)

The low-pressure center of a hurricane containing relatively clear, calm, rising air. It usually has light winds, low precipitation, and low pressure.

storm surge

A higher than normal local sea level caused by seawater flowing toward the lower air pressure under a hurricane.

station model

A symbolic representation of data from a weather station on a weather map; each number and symbol, and their locations in the model, provide specific provide specific weather information

synoptic weather map

A weather map that presents a summary or synopsis of weather data for a given time frame

source region

where air masses gain their temperature and humidity

cold front

when a cold air mass replaces a warm air mass

weather associated with cumulonimbus clouds

tornadoes, thunderstorms, and lightening

greatest source of destruction in-land from a hurricane

high wind speeds

if caught outside in a thunderstorm you should...

crouch down on the ground in an open area away from trees

Nor'easter

a winter storm system that brings snow in from the Atlantic Ocean

supercell

strong rotating cloud systems that form tornadoes

what makes tornadoes so destructive

wind speed and updrafts

tropical cyclones and storms

the kind of storms that are assigned names

occluded front

When a warm air mass is trapped between two colliding colder air masses

wintry mix

sequence of different kinds of precipitation during winter storms

tornado base

part of the tornado is the most destructive

isobars

map with lines connecting areas of same pressure

isotherms

map with lines connecting areas of same temperature

isohyet

map with lines connecting areas of same rain fall

storm swell

huge waves that precede a hurricane

eye wall

winds are strongest in this part of a hurricane

4 synoptic weather maps

Surface Weather map, Highest and Lowest Temperatures map, Precipitation Areas and Amounts map, and 500 Millibar Height Contours map

warm front

when a warm air mass overtakes a cold air mass

high pressure system weather

Sunny, clear skies Calm winds, spiral clockwise Cool, dry air

low pressure system weather

Cloudy, stormy skies Strong winds, spiral counterclockwise Warm, moist air

N, NW or W

directions from which cold air masses tend to approach

S, SE or E

directions from which warm air masses tend to approach

4 ways in which air can be lifted

convection, orographic lifting, frontal wedging, convergence