Air Masses, Fronts, and Severe Weather Flashcards 6th

What are air masses?

Air masses are large bodies of cold or moist air with properties that are determined by the part of Earths surface over which it develops.

Do air masses always move in the same or different directions?

Different

When air masses bump into each other what happens?

Rain, thunderstorms, snow, or tornadoes

What is a front?

A front is an air mass that collides with another air mass and a boundary forms between them.

The movement and collision of air masses causes _______.

Weather conditions to change.

When does a cold front occur?

When a cold air mass advances towards a warm air mass

During a cold front, does cold air replace warm air or the other way around?

Cold air replaces warmer air.

In the U.S. cold fronts move __ to __.

NW, SE

What happens to air once a cold front moves in?

It gets drier.

What happens during cold fronts?

Severe thunderstorms

When does a warm front occur?

When a warm air mass meets a cold air mass

Does cold air replace warm air during a warm front or the other way around?

Warm air replaces colder air

Which direction do warm fronts travel?

SW to NE

What happens to the air after a warm front moves in?

It becomes more humid

What is a stationary front?

When a cold or warm front stops moving

What is an occluded front?

When two cold air masses meet and trap warm air between them

What does an occluded front usually result in?

storms

In the U.S. colder air lies to the ____.

West

What do high pressure systems bring?

Clear weather

What is the density of air in high pressure systems?

Air particles are more densely packed

High pressure causes air to ____. As it _____, it becomes ________, so it can hold more water vapor. Humidity of warmer air _______, and droplets of water in clouds evaporate.

Sink, sinks, warmer, decreases.

Low pressure systems bring:

Cloudy, rainy weather

Low pressure systems are pushed _____ by ______ dense air (high pressure systems) . As it gains altitude, air _____, humidity _______, _______ takes place and clouds form.

upward, more, cools, increases ,condensation

Thunderstorms are formed by:

The rapid upward movement of warm, moist air. Warm moist air powers all thunderstorms.

What front to thunderstorms usually occur at?

Cold fronts

What clouds make thunderstorms?

Cumulonimbus clouds

How do thunderstorms form?

Thunderstorms produce water droplets that form in clouds and begin falling towards Earth. These water droplets collide with others while they are falling and create larger raindrops. The falling droplets cause a downward motion of air that spread out as Earth's surface causing strong winds.

What is lightning?

Lightning is electricity which occurs when current flows between regions of opposite electrical charge.

Lightning can happen:

Between two clouds, from a cloud to Earth's surface or from Earth's surface to a cloud

Lightning tends to strike ______ buildings.

Taller

Thunder happens because:

The result of rapid heating of the air around a lightning bolt. The air close by expands, forming a sound wave.

What shape are tornadoes?

Funnel shaped

How do tornadoes form?

Thunderstorms produce rapid upward movement of warm moist air. The upward moving air is twisted when it comes in contact with cooler winds in different directions. As the speed of the rotating mass increases, warm air is is drawn to the low-pressure at its center. The funnel-shaped cloud extends down, touching the ground.

What are hurricanes?

Large, swirling low pressure systems that form over tropical oceans.

How do hurricanes form (big idea)?

Rising warm air

How do hurricanes form (detailed)?

They form over tropical oceans, where two opposing winds begin to blow. A low pressure system forms in the middle and starts rotating, Warm moist air is pushed up the middle. Dropping air pressure brings air to the center causing winds and lower pressure.

What is a drought?

A prolonged period of abnormally low rainfall leading to less rainfall.

How do droughts form?

Droughts form slowly over time. They are difficult to predict