Weather Chapter 25 Modern Earth Science. Fronts Chapter 25 Section 2 EQ: What are some of the possible outcomes from fronts coming together?

WeatherWeather

Chapter 25Chapter 25

Modern Earth ScienceModern Earth Science

FrontsFronts

Chapter 25 Section 2Chapter 25 Section 2

EQ: What are some of the EQ: What are some of the possible outcomes from fronts possible outcomes from fronts

coming together?coming together?

Section 25.2 ObjectivesSection 25.2 Objectives

CompareCompare the characteristic weather the characteristic weather patterns of cold fronts with those of patterns of cold fronts with those of warm fronts.warm fronts.

DescribeDescribe how a midlatitude cyclone how a midlatitude cyclone forms.forms.

DescribeDescribe the development of the development of hurricanes, thunderstorms, and hurricanes, thunderstorms, and tornadoes.tornadoes.

FrontsFronts A A cool air masscool air mass is dense and is dense and does not mixdoes not mix

with the less-dense air of a warm air mass.with the less-dense air of a warm air mass.

a a front front is a boundary that forms between is a boundary that forms between air masses.air masses.

Middle-latitude weather changes usually Middle-latitude weather changes usually take place along the various types of take place along the various types of fronts. fronts.

Fronts do not exist in the Tropics because Fronts do not exist in the Tropics because no air masses that have significant no air masses that have significant temperature differences exist there.temperature differences exist there.

Cold & Warm FrontsCold & Warm Fronts

cold front cold front the front edge of a moving mass the front edge of a moving mass of cold air that pushes beneath a warmer of cold air that pushes beneath a warmer air mass like a wedgeair mass like a wedge

If the warm air is moist, clouds will form. If the warm air is moist, clouds will form.

warm front warm front the front edge of advancing the front edge of advancing warm air mass that replaces colder air warm air mass that replaces colder air with warmer airwith warmer air

A warm front generally produces A warm front generally produces precipitation over a large area and may precipitation over a large area and may cause violent weather.cause violent weather.

Stationary and Occluded FrontsStationary and Occluded Fronts

stationary front stationary front a front of air a front of air masses that moves either very masses that moves either very slowly or not at allslowly or not at all

occluded front occluded front a front that forms a front that forms when a cold air mass overtakes a when a cold air mass overtakes a warm air mass and lifts the warm air warm air mass and lifts the warm air mass off the ground and over mass off the ground and over another air massanother air mass

Polar FrontsPolar Fronts

The boundary where cold polar air The boundary where cold polar air meets the tropical air mass of the meets the tropical air mass of the middle latitudes, especially over the middle latitudes, especially over the ocean, is called the ocean, is called the polar frontpolar front..

Waves commonly develop along the Waves commonly develop along the polar front. polar front.

AA wave wave is a bend that forms in a cold is a bend that forms in a cold front or stationary front.front or stationary front.

Wave CyclonesWave Cyclones

midlatitude cyclone midlatitude cyclone an area of low an area of low pressure that is characterized by rotating pressure that is characterized by rotating wind that moves toward the rising air of wind that moves toward the rising air of the central low-pressure regionthe central low-pressure region

Waves are the beginnings of low-pressure Waves are the beginnings of low-pressure storm centers called midlatitude cyclones storm centers called midlatitude cyclones or or wave cycloneswave cyclones..

These cyclones strongly influence weather These cyclones strongly influence weather patterns in the middle latitudes.patterns in the middle latitudes.

Wave CyclonesWave Cyclones

ThunderstormsThunderstorms

thunderstorm thunderstorm a usually brief, heavy a usually brief, heavy storm that consists of rain, strong storm that consists of rain, strong winds, lightning, and thunderwinds, lightning, and thunder

T-storms develop in three distinct T-storms develop in three distinct stages.stages.

The t-storm dissipates as the supply The t-storm dissipates as the supply of water vapor decrease.of water vapor decrease.

LightningLightning

During a t-storm, clouds discharge During a t-storm, clouds discharge electricity in the form of electricity in the form of lightninglightning..

The released electricity heats the air, and The released electricity heats the air, and the air rapidly expands and produces a the air rapidly expands and produces a loud noise known as loud noise known as thunderthunder..

For lightning to occur, the clouds must For lightning to occur, the clouds must have areas that carry distinct electrical have areas that carry distinct electrical charges. charges.

HurricanesHurricanes hurricane hurricane a severe storm that develops a severe storm that develops

over tropical oceans and whose strong over tropical oceans and whose strong winds of more than 120 km/h spiral in winds of more than 120 km/h spiral in toward the intensely low-pressure storm toward the intensely low-pressure storm centercenter

A hurricane begins when warm, moist air A hurricane begins when warm, moist air over the ocean rises rapidly.over the ocean rises rapidly.

When moisture in the rising warm air When moisture in the rising warm air condenses, a large amount of energy in condenses, a large amount of energy in the form of the form of latent heatlatent heat is released. This is released. This heat increases the force of the rising air.heat increases the force of the rising air.

TornadoesTornadoes

tornado tornado a destructive, rotating column of a destructive, rotating column of air that has very high wind speeds and air that has very high wind speeds and that maybe visible as a funnel-shaped that maybe visible as a funnel-shaped cloudcloud

The smallest, most violent, and shortest-The smallest, most violent, and shortest-lived severe storm is a tornado.lived severe storm is a tornado.

A tornado forms when a thunderstorm A tornado forms when a thunderstorm meets high-altitude horizontal winds. meets high-altitude horizontal winds. These winds cause the rising air in the These winds cause the rising air in the thunderstorm to rotate.thunderstorm to rotate.