Storms Chapter 13 Section 4. Essential Questions Chap 13 Sec 4 1.What are the main kinds of storms, and how do they form? 2.What measures can you take.

StormsStormsChapter 13Chapter 13

Section 4Section 4

Essential QuestionsEssential QuestionsChap 13 Sec 4Chap 13 Sec 4

1.1. What are the main kinds of storms, and What are the main kinds of storms, and how do they form?how do they form?

2.2. What measures can you take to ensure What measures can you take to ensure safety in a storm?safety in a storm?

StormsStorms

StormsStorms

A storm is a violent disturbance in the A storm is a violent disturbance in the atmosphereatmosphere

It is involves sudden changes in air It is involves sudden changes in air pressure, which can cause rapid air pressure, which can cause rapid air movementsmovements

There are several types of stormsThere are several types of storms

Types of StormsTypes of Storms

ThunderstormsThunderstorms TornadoesTornadoes Snow StormsSnow Storms HurricanesHurricanes

ThunderstormsThunderstorms

ThunderstormsThunderstorms Thunderstorms are small storms with heavy Thunderstorms are small storms with heavy

precipitation and frequent thunder & precipitation and frequent thunder & lightninglightning

Many thunderstorms form in the spring and Many thunderstorms form in the spring and summer in southern states and on the summer in southern states and on the Western PlainsWestern Plains

Thunderstorms form in large cumulonimbus Thunderstorms form in large cumulonimbus clouds (either on hot, humid afternoons or clouds (either on hot, humid afternoons or when cold fronts pass through)when cold fronts pass through)

How thunderstorms form:How thunderstorms form:

Warm, humid air rises rapidlyWarm, humid air rises rapidly The air cools, forming dense thunderheads The air cools, forming dense thunderheads

(cumulonimbus clouds)(cumulonimbus clouds) Heavy rain and sometimes hail fallsHeavy rain and sometimes hail falls The clouds contain strong upward and The clouds contain strong upward and

downward winds (called updrafts and downward winds (called updrafts and downdrafts)downdrafts)

Thunderstorms contain thunder & lightningThunderstorms contain thunder & lightning

Stages in the Development Stages in the Development of a Thunderstormof a Thunderstorm

Thunder & lightningThunder & lightning Lightning is a sudden spark (an electrical Lightning is a sudden spark (an electrical

discharge) as positive and negative charges discharge) as positive and negative charges jump between parts of a cloud, between nearby jump between parts of a cloud, between nearby clouds, or between a cloud and the groundclouds, or between a cloud and the ground

Thunder is caused by the superfast heating of Thunder is caused by the superfast heating of the air by lightningthe air by lightning– Lightning heats the air around it to 30,000° C (much Lightning heats the air around it to 30,000° C (much

hotter than the surface of the sun)hotter than the surface of the sun)– The rapidly heated air expands suddenly and The rapidly heated air expands suddenly and

explosivelyexplosively– Thunder is the sound of the explosionThunder is the sound of the explosion

Because light travels much faster than sound, Because light travels much faster than sound, you see lightning before you hear thunderyou see lightning before you hear thunder

Calculate the distance of lightning:Calculate the distance of lightning:

Count the number of seconds between the Count the number of seconds between the moment you see the lightning and when you moment you see the lightning and when you hear the thunderhear the thunder

Divide that number by 5 to get the Divide that number by 5 to get the approximate distance in milesapproximate distance in miles– Example: 15 seconds divided by 5 = 3 milesExample: 15 seconds divided by 5 = 3 miles

Do this inside!!!!!!!Do this inside!!!!!!!

Damage & Danger from Damage & Danger from Thunderstorms:Thunderstorms:

Heavy rains can cause floodingHeavy rains can cause flooding Lightning can strike and damage trees, Lightning can strike and damage trees,

homes, electronics in our homes, animals, homes, electronics in our homes, animals, and peopleand people

Lightning can start firesLightning can start fires When it strikes people and animals, it can When it strikes people and animals, it can

cause unconsciousness, serious burns, or cause unconsciousness, serious burns, or even heart failureeven heart failure

FloodsFloods Floods are caused by too much water pouring Floods are caused by too much water pouring

into streams and rivers at onceinto streams and rivers at once In cities floods can be caused by lack of ground In cities floods can be caused by lack of ground

to absorb the water (covered with roads, to absorb the water (covered with roads, buildings, etc)buildings, etc)

If the ground is already soaked because of If the ground is already soaked because of previous rains it is more likely to floodprevious rains it is more likely to flood

Floods can destroy human structures and Floods can destroy human structures and wildlife habitatswildlife habitats

Floods can be good! They can provide rich new Floods can be good! They can provide rich new soil for agriculturesoil for agriculture

Safety during ThunderstormsSafety during Thunderstorms Go inside Go inside Avoid touching telephones, electrical appliances, Avoid touching telephones, electrical appliances,

or plumbing fixtures (all conduct electricity)or plumbing fixtures (all conduct electricity) Cars are generally safe if they have a hard top Cars are generally safe if they have a hard top

because the electricity will flow along the metal because the electricity will flow along the metal surface of the car to the groundsurface of the car to the ground

Avoid metal objects, tall structures, and bodies Avoid metal objects, tall structures, and bodies of water such as:of water such as:– Trees, poles, high hills, fences, being in pools or lakes Trees, poles, high hills, fences, being in pools or lakes

(even in a boat)(even in a boat) Get in a low area as close to the ground as Get in a low area as close to the ground as

possiblepossible

TornadoesTornadoes

All About TornadoesAll About Tornadoes

A frightening and destructive stormA frightening and destructive storm A rapidly whirling, funnel-shaped cloud that A rapidly whirling, funnel-shaped cloud that

reaches down from a storm cloud to touch Earth’s reaches down from a storm cloud to touch Earth’s surfacesurface

A waterspout is a tornado over a lake or oceanA waterspout is a tornado over a lake or ocean Tornadoes usually touch the ground for 15 Tornadoes usually touch the ground for 15

minutes or less and are usually only a few minutes or less and are usually only a few hundred meters acrosshundred meters across

Winds in the tornado reach up to 500 kilometers Winds in the tornado reach up to 500 kilometers per hour (311 mph)per hour (311 mph)

How Tornadoes FormHow Tornadoes Form

Tornadoes usually develop in cumulonimbus Tornadoes usually develop in cumulonimbus clouds just like thunderstorms, but can clouds just like thunderstorms, but can develop in any situation that produces develop in any situation that produces severe weathersevere weather

They are most likely to occur in the spring They are most likely to occur in the spring and early summer, often late in the and early summer, often late in the afternoon when the ground is warm (just like afternoon when the ground is warm (just like thunderstorms)thunderstorms)

Formation continuedFormation continued

A special situation on the Great Plains creates A special situation on the Great Plains creates perfect weather for tornadoes to formperfect weather for tornadoes to form– A warm, humid air mass moves north from the Gulf of A warm, humid air mass moves north from the Gulf of

Mexico into the lower Great PlainsMexico into the lower Great Plains– A cold, dry air mass moves south from CanadaA cold, dry air mass moves south from Canada– When the air masses meet, the cold air moves under When the air masses meet, the cold air moves under

the warm air, forcing it to risethe warm air, forcing it to rise– A squall line (narrow band of thunderstorms) is formed A squall line (narrow band of thunderstorms) is formed

and the storms travel from southwest to northeastand the storms travel from southwest to northeast– A single squall line can produce ten or more tornadoesA single squall line can produce ten or more tornadoes

Tornado AlleyTornado Alley

The US has more tornadoes per year than The US has more tornadoes per year than any other country (about 800)any other country (about 800)

Tornadoes occur in nearly every part of Tornadoes occur in nearly every part of the USthe US

Because of the warm air from the Gulf of Because of the warm air from the Gulf of Mexico and the cold air from Canada, Mexico and the cold air from Canada, there is Tornado Alleythere is Tornado Alley– It includes Texas, Oklahoma, Kansas, It includes Texas, Oklahoma, Kansas,

Nebraska, and Iowa (and a very small area of Nebraska, and Iowa (and a very small area of South Dakota). See page 453 for a map.South Dakota). See page 453 for a map.

Tornado SafetyTornado Safety

The safest place to be is in a storm shelter or the The safest place to be is in a storm shelter or the basement of a well-built buildingbasement of a well-built building

Stay away from windows and doors and avoid Stay away from windows and doors and avoid flying debrisflying debris

Lie on the floor under a sturdy piece of furniture Lie on the floor under a sturdy piece of furniture (such as a strong table)(such as a strong table)

Outside – lie flat in a ditchOutside – lie flat in a ditch Don’t take cover under an overpass or bridge Don’t take cover under an overpass or bridge

(the forces are actually strengthened here)(the forces are actually strengthened here) There is usually little warning of a tornado – take There is usually little warning of a tornado – take

shelter immediately if you hear of a warningshelter immediately if you hear of a warning

Tornadoes

20.320.3 Severe Storms Severe Storms

Tornado Intensity

Tornado Safety• Tornado watches alert people to the possibility of

tornadoes in a specified area for a particular time.

• Because tornado winds cannot be measured directly, a rating on the Fujita scale is determined by assessing the worst damage produced by the storm.

• A tornado warning is issued when a tornado has actually been sighted in an area or is indicated by weather radar.

Fujita Tornado Intensity ScaleFujita Tornado Intensity Scale

SnowstormsSnowstorms

SnowstormsSnowstorms

All year, most precipitation begins in clouds as All year, most precipitation begins in clouds as snow!! If the air is colder than 0° C all the way to snow!! If the air is colder than 0° C all the way to the ground, the precipitation falls as snow.the ground, the precipitation falls as snow.

A snowstorm has high winds blowing the snow A snowstorm has high winds blowing the snow and even picking up snow from the ground and and even picking up snow from the ground and blowing it back into the airblowing it back into the air

It is easy to become lost in a snowstorm because It is easy to become lost in a snowstorm because of poor visibilityof poor visibility

Strong winds cool a person’s body rapidlyStrong winds cool a person’s body rapidly

Snowstorm SafetySnowstorm Safety

Try to find shelter from the windTry to find shelter from the wind Cover exposed parts of your body and try to Cover exposed parts of your body and try to

stay drystay dry If in a car, only run the engine if the exhaust If in a car, only run the engine if the exhaust

pipe is clear of snowpipe is clear of snow

HurricanesHurricanes

Satellite View of Hurricane FloydSatellite View of Hurricane Floyd

HurricaneHurricane

A tropical cyclone (remember from last A tropical cyclone (remember from last week) that has winds of 119 km/h week) that has winds of 119 km/h (kilometers per hour) or (74 mph)(kilometers per hour) or (74 mph)

A typical hurricane is about 600 km (373 A typical hurricane is about 600 km (373 miles) acrossmiles) across

Hurricanes form in the Atlantic, Pacific, and Hurricanes form in the Atlantic, Pacific, and Indian oceansIndian oceans– Called typhoons in the western Pacific OceanCalled typhoons in the western Pacific Ocean– Called cyclones in the Indian OceanCalled cyclones in the Indian Ocean

How Hurricanes FormHow Hurricanes Form

A hurricane begins over warm ocean water A hurricane begins over warm ocean water as a low-pressure area (called a tropical as a low-pressure area (called a tropical disturbance)disturbance)

If the tropical disturbance grows in size and If the tropical disturbance grows in size and strength it becomes a tropical storm, then strength it becomes a tropical storm, then can become a hurricanecan become a hurricane

Hurricanes that strike the US usually form in Hurricanes that strike the US usually form in the Atlantic Ocean north of the equator near the Atlantic Ocean north of the equator near Africa in August, September, or OctoberAfrica in August, September, or October

Formation ContinuedFormation Continued

Warm, humid air at the ocean’s surface rises and forms Warm, humid air at the ocean’s surface rises and forms cloudsclouds

The rising air draws more warm, moist air into the systemThe rising air draws more warm, moist air into the system Inside the storm are bands of very high winds and heavy Inside the storm are bands of very high winds and heavy

rainrain Winds spiral inward toward the area of lowest pressure at Winds spiral inward toward the area of lowest pressure at

the centerthe center The lower the air pressure at the center of a storm, the The lower the air pressure at the center of a storm, the

faster the winds blow toward the centerfaster the winds blow toward the center Hurricane winds may be as strong as 320 km/h (199 mph)Hurricane winds may be as strong as 320 km/h (199 mph)

Structure of the HurricaneStructure of the Hurricane

The hurricane has bands of very high winds and The hurricane has bands of very high winds and heavy rainsheavy rains

The narrow band around the center of the storm The narrow band around the center of the storm has the strongest windshas the strongest winds

At the center of the storm is a ring of clouds called At the center of the storm is a ring of clouds called the eyewall which encloses a quiet “eye”the eyewall which encloses a quiet “eye”– The winds get stronger as the eye approachesThe winds get stronger as the eye approaches– When the eye arrives, the weather suddenly changes to When the eye arrives, the weather suddenly changes to

calm air and possibly clear skiescalm air and possibly clear skies– After the eye passes, the storm resumes, but the wind After the eye passes, the storm resumes, but the wind

blows from the opposite directionblows from the opposite direction

Cross Section of a HurricaneCross Section of a Hurricane

How Hurricanes MoveHow Hurricanes Move Hurricanes last much longer than other storms Hurricanes last much longer than other storms

(usually a week or more)(usually a week or more) They travel a far distance over the ocean before They travel a far distance over the ocean before

making “Landfall”making “Landfall” Hurricanes formed in the Atlantic Ocean are Hurricanes formed in the Atlantic Ocean are

steered by trade winds toward the Caribbean steered by trade winds toward the Caribbean Islands and the southeastern US (that is us!)Islands and the southeastern US (that is us!)

After a hurricane moves over land, it loses its After a hurricane moves over land, it loses its supply of warm, humid air and gradually loses supply of warm, humid air and gradually loses strenghtstrenght

Even after losing strength, it can carry heavy Even after losing strength, it can carry heavy rainfall for long distances over several days rainfall for long distances over several days

Hurricane DamageHurricane Damage Hurricanes bring high waves, severe flooding, Hurricanes bring high waves, severe flooding,

damaging winds, and even tornadoes as they damaging winds, and even tornadoes as they come ashorecome ashore

In the area of the hurricane while over the In the area of the hurricane while over the ocean, low pressure and high winds can raise ocean, low pressure and high winds can raise water up to 6 meters (20 feet) above normal sea water up to 6 meters (20 feet) above normal sea levellevel– As the hurricane makes landfall, a huge dome of As the hurricane makes landfall, a huge dome of

water called a storm surge sweeps across the coast water called a storm surge sweeps across the coast where the hurricane landswhere the hurricane lands

– Storm surge is the most deadly part of a hurricane Storm surge is the most deadly part of a hurricane where it makes landfallwhere it makes landfall

– Storm surges can cause great damage, washing Storm surges can cause great damage, washing away beaches, destroying buildings along the coast, away beaches, destroying buildings along the coast, and eroding coastlinesand eroding coastlines

Hurricane SafetyHurricane Safety Prior to the 1950s people had little warning Prior to the 1950s people had little warning

about hurricanes because of a lack of about hurricanes because of a lack of technologytechnology

Today, we watch hurricanes move across Today, we watch hurricanes move across the ocean for daysthe ocean for days

Cities will issue hurricane warnings when Cities will issue hurricane warnings when hurricane conditions are expected with 24 hurricane conditions are expected with 24 hourshours– Citizens are often told to evacuate which Citizens are often told to evacuate which

means they should leave the area means they should leave the area immediatelyimmediately

Hurricanes

20.320.3 Severe Storms Severe Storms

Hurricane Intensity• The intensity of a hurricane is described using

the Saffir-Simpson scale.

• A storm surge is the abnormal rise of the sea along a shore as a result of strong winds.

Saffir-Simpson Hurricane ScaleSaffir-Simpson Hurricane Scale

Essential Questions AnsweredEssential Questions AnsweredChap 13 Sec 4Chap 13 Sec 4

1.1. What are the main kinds of storms, and What are the main kinds of storms, and how do they form?how do they form?

Thunderstorms – form when warm, humid air Thunderstorms – form when warm, humid air rises quicklyrises quickly

Tornadoes – form in cumulonimbus cloudsTornadoes – form in cumulonimbus clouds Hurricanes – form in low-pressure areas over Hurricanes – form in low-pressure areas over

the oceanthe ocean Snowstorms – form when it is really cold, Snowstorms – form when it is really cold,

windy, and snowingwindy, and snowing

Essential QuestionsEssential QuestionsChap 13 Sec 4Chap 13 Sec 4

2.2. What measures can you take to ensure What measures can you take to ensure safety in a storm?safety in a storm?

Thunderstorm – stay inside, avoid water & Thunderstorm – stay inside, avoid water & electricityelectricity

Tornadoes – storm cellar, basement, avoid cars, Tornadoes – storm cellar, basement, avoid cars, windows, and doorswindows, and doors

Hurricanes – evacuateHurricanes – evacuate

Snowstorms – find shelter, no exposed body partsSnowstorms – find shelter, no exposed body parts

Section 5 – Predicting the Section 5 – Predicting the WeatherWeather

Essential Questions (Ch 13 S 5)Essential Questions (Ch 13 S 5)

1.1. How do weather forecasters How do weather forecasters predict the weather?predict the weather?

Collect DataCollect Data Collect data about clouds, air pressure, and Collect data about clouds, air pressure, and

other weather readingsother weather readings Analyze the data to predict what will happen Analyze the data to predict what will happen

nextnext Meteorologists are scientists that study the Meteorologists are scientists that study the

causes of weather and try to predict itcauses of weather and try to predict it– They use maps, charts, and computers to analyze They use maps, charts, and computers to analyze

weather data and to prepare weather forecastsweather data and to prepare weather forecasts– Data is collected by local weather observers, Data is collected by local weather observers,

instruments carried by balloons, satellites, and instruments carried by balloons, satellites, and weather stations around the worldweather stations around the world

– The National Weather Service owns much of the The National Weather Service owns much of the equipment and provides data to the meteorologistsequipment and provides data to the meteorologists

You can collect data too:You can collect data too: Observe air pressure. Falling air pressure Observe air pressure. Falling air pressure

usually indicates an approaching low-pressure usually indicates an approaching low-pressure area, possibly bringing rain or snowarea, possibly bringing rain or snow

Observe clouds. Thin cirrus clouds high in the Observe clouds. Thin cirrus clouds high in the sky indicate a warm front may be approaching. sky indicate a warm front may be approaching. Cumulus clouds growing taller and taller on a Cumulus clouds growing taller and taller on a warm afternoon can become cumulonimbus warm afternoon can become cumulonimbus clouds and produce thunderstormsclouds and produce thunderstorms

A red sky at sunrise might indicate an A red sky at sunrise might indicate an approaching low-pressure area and stormy approaching low-pressure area and stormy weatherweather

A red sky at sunset often indicates storms are A red sky at sunset often indicates storms are moving away and clear weather is aheadmoving away and clear weather is ahead

Weather MapsWeather Maps The National Weather Service assembles The National Weather Service assembles

weather maps using data from all over the weather maps using data from all over the countrycountry

Isobars are lines often found on weather maps. Isobars are lines often found on weather maps. These lines show areas having the same air These lines show areas having the same air pressure. Iso means equal and bar means pressure. Iso means equal and bar means pressure. Measurement may be in inches or pressure. Measurement may be in inches or mercury, millibars, or both.mercury, millibars, or both.

Isotherms show areas have the same Isotherms show areas have the same temperature.temperature.

Weather maps have symbols to show fronts, Weather maps have symbols to show fronts, areas of high and low pressure, types of areas of high and low pressure, types of precipitation, and temperaturesprecipitation, and temperatures

See the weather map on page 463See the weather map on page 463

Limits of Weather ForecastsLimits of Weather Forecasts

Computers, satellites, and radar have made Computers, satellites, and radar have made weather monitoring and predicting much weather monitoring and predicting much betterbetter

However, we will probably never be able to However, we will probably never be able to predict the weather a month in advance predict the weather a month in advance because just a small change today can because just a small change today can create big changes several days latercreate big changes several days later

The Butterfly EffectThe Butterfly Effect

A scientist once suggested that even the A scientist once suggested that even the flapping of a butterfly’s wings causes a tiny flapping of a butterfly’s wings causes a tiny disturbance in the atmosphere. This tiny disturbance in the atmosphere. This tiny event might cause a larger disturbance that event might cause a larger disturbance that could grow into a large storm.could grow into a large storm.

Essential Questions AnsweredEssential Questions Answered(Ch 13 S 5)(Ch 13 S 5)

1.1. How do weather forecasters How do weather forecasters predict the weather?predict the weather?

They make observations, collect They make observations, collect weather data, and interpret the weather data, and interpret the data to make their predictionsdata to make their predictions

ReviewReview

1.1. What is the name of a scientist that studies What is the name of a scientist that studies and predicts weather?and predicts weather?

2.2. Which type of storm develops over the Which type of storm develops over the ocean over warm, humid air?ocean over warm, humid air?

3.3. Which type of storm usually develops Which type of storm usually develops inside a cumulonimbus cloud over land inside a cumulonimbus cloud over land and has strong, swirling winds?and has strong, swirling winds?

4.4. Which type of storm produces heavy rain, Which type of storm produces heavy rain, thunder, and lightning?thunder, and lightning?