Why do we have weather? 1. The sun is what causes us to have weather. As solar energy reaches the Earth, the air masses at the equator heat up more than at the poles. 2. Warm air and water at the equator travel toward the poles 3. Cold air and water at the poles travel toward equator 4. It is the atmosphere's struggle for temperature balance that brings us our changing weather.

The Atmosphere’s Struggle

An air mass is a large dome of air which has similar temperature and moisture characteristics.

What is a storm? Storms are very simple to understand Areas in our atmosphere that have low air-pressure and winds that spiral in toward the center form the many different types of storms.

Types of storms Extratropical storms:  Form outside the tropics  Center of storm is colder than the surrounding air  Has fronts  Strongest winds in the upper atmosphere  Causes tornadoes, thunderstorms Tropical storms:  Form over a tropical ocean  Center of storm is warmer than the surrounding air than the surrounding air  Has no fronts  Strongest winds are near the Earth's surface the Earth's surface  Causes hurricanes, typhoons

What is a Front? When 2 air masses with different properties meet and do not combine together, the area between them is called a front. There are 4 types of fronts: Cold Front Warm Front Occluded Front Stationary Front

What is a cold front? A Cold Front… forms when warm air moves up, and cold air rushes in beneath it. the air masses crash together and the cold front goes down and the warm front goes up.

A Warm Front forms… A Warm Front forms… …when a mass of warm air overtakes a cold air mass and moves over it. Steady rain and light showers usually are associated with Warm Fronts.

What do they mean by Occluded? To occlude means to block or hide someone or something. An Occluded Front… o forms when a Cold Front overtakes a Warm Front. o produces less extreme weather such as rain and wind

Since a cold front is the boundary between cool and warm air when the cool air is replacing the warm air, and a warm front is the boundary when the warm air is winning the battle in the sky…what happens when neither one is winning? This known as a stationary front. Stationary fronts often bring several days of cloudy, wet weather that can last a week or more The Tale of the Fighting Fronts

A Tornado is… A violent whirling wind, extending from the base of a thunderstorm cloud to the ground. 2. A tornado over a lake or ocean is called a waterspout.

Tornadoes The most destructive winds – speeds of up to 310 mph -- faster than Indy 500 race cars Winds act like a vacuum -- sucks up air that crashes together and spins

…..After Before…

Microbursts  Very concentrated bursts of air that blast down from thunderstorms.

 In a Microburst, air falls at speeds of 90 mph (in normal storms air falls about 10 mph)

The name "monsoon" comes from an Arabic word which means "season" or "wind-shift". Arizona Monsoons occur during the late summer months. In the winter, wind flows to Arizona from California and Nevada. In the summer, the winds shift bringing moisture from the Pacific Ocean and the Gulf of Mexico. This change, together with daytime heating, brings Arizona monsoons.

How a Monsoon forms

Are Monsoons only in Arizona? No, the most well known monsoons are those which affect India and Southeast Asia. The summer monsoon blows southwest across the Indian Ocean and is extremely wet. The winter monsoon blows northeasterly and is generally dry.

Dust Devils Look like mini tornadoes, but tornadoes form high in the sky, devils form on the ground Happens when ground gets really hot and heats up air;air rises fast and bangs together, spinning around Sucks up dust and dirt Fastest devils spin about 40 mph

Hurricanes are actually a kind of Tropical Storms Tropical storms are large rotating storm systems that form in the Atlantic, Indian, and Pacific oceans.  In the Atlantic and eastern Pacific they are called hurricanes. Pacific they are called hurricanes.  In the western Pacific they are known as typhoons, which means known as typhoons, which means “great winds” in Chinese. “great winds” in Chinese.  Those in the Indian Ocean are called cyclones, or by Australians, called cyclones, or by Australians, willy-willies. willy-willies.  No matter which term is used, they all describe this phenomenon all describe this phenomenon

How a hurricane begins

Great Hurricane of 1938  The eye was about 50 miles across and the hurricane was about 500 miles wide.  Winds gusting over 180 mph and waves between 30 and 50 feet pounded the coastline with millions of tons of sea water.  Entire homes and families were swept into the sea.  Most people did not even realize that a hurricane was upon them even as the waters began flooding their coastal homes.  Providence, Rhode Island was 20 feet underwater while Westhampton Beach, a mile inland, was under 8 feet of water!

Types of Precipitation  Rain - Liquid drops of water which fall from the clouds  Snow - Falling ice formed when water vapor turns into ice.  Sleet - Drops of rain that freeze into ice as they fall.  Hail - Falling ice balls formed during thunderstorms.

Snowstorms

Rainstorms and Snowstorms Rainstorms and Snowstorms are produced when two different fronts collide. (A warm hitting a cold or a cold hitting a warm.) Major effects could be huge blizzards, ice storms and heavy rainstorms also known as Monsoons.

Blizzards In the winter, when a warm front moves in and meets a cold front, clouds develop and heavy snowfall occurs. There are ice crystals in clouds. When many tiny crystals build up, they fall to the Earth as snow. A blizzard is a name for a violent, bitterly cold wind with blowing snow whipped up from the ground.

What makes a snowstorm into a blizzard? A snowstorm becomes a blizzard when you can’t see very far ahead of you for three or more hours. Winds of 35 mph or more along with lots of falling and/or blowing snow Temperature of less than 20 degrees

Thunderstorms  Thunderstorms are produced when cold fronts move in and meet warm fronts.  Thunderstorms are heavy rainstorms accompanied by thunder and lightning.

Thunder and Lightning Thunder is created when lightning heats up the air around it and causes it to expand rapidly. Since light travels very fast, you see lightning as it happens. Sound travels much slower than light and takes much longer to get to you. You hear the thunder after you see the lightning. It takes thunder 5 seconds to travel one mile. After you see a flash of lightning, start counting seconds until you hear the thunder. Divide the number of seconds by 5. This is the number of miles away the lightning is.

Hailstorms and Hailstones Hail forms when strong currents of rising air carry rain from thunderstorms upwards where it freezes into ice. Hail often melts before it reaches the ground, but in sometimes ice chunks the size of softballs pound the countryside

Floods A flood occurs when a body of water rises and overflows onto normally dry land.

Coastal Flooding Caused by high, wind- generated water waves, high tides, erosion of coastal areas, and tsunamis (underwater earthquakes). Coastal flooding is a big concern because, in many people live along coastlines all over the world.

River Flooding When it rains and snow melts, the soil can only absorb water a certain amount of water in a short period of time. The longer it rains, the more likely it is that rainwater will build up on the ground as runoff and overflow lakes, rivers and streams.

Caused by extremely intense rainfall, 10 inches or more an hour, for a short period of time. Common in mountainous areas, where steep slopes cause water to travel at high speeds, causing erosion. These floods often occur with little warning. Flash Floods

Is there anything good about a flood? Floods cause disasters, but they can also be beneficial. When a river overflows, it dumps sand, silt and debris that is carried downstream onto the surrounding land. After the flood waters move away, the soil is more fertile, because of the organic matter and minerals that were in the water.