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_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 2 _ 8 8 9 4 0 edn setas ete Weather Reading Essentials Pressure Systems Weather Patterns Weather forms. and sometimesprecipitation,suchasrainorsnow, also rising aircoolsandthewatervaporcondenses.Cloudsform, This causesairinsidethelow-pressuresystemtorise.The the outsideofsystemwillspiralintowardcenter. pressure atitscenter andhigherpressure outsideofthesystem brings clearskiesandfairweather. . Thedenseairinsidethehighpressuresystemsinksand from areasofhighpressuretolowiscalled inside thesystemmovesawayfromcenter. Airmoving from highpressuretolowpressure.Heavy, high-pressureair pressure atitscenter andlower pressure outsideof the system low pressure. weight, thanwarmairmassesdo.Warm airmasseshave molecules. Coolairmasseshavehighpressure,ormore air. Cool airmoleculesareclosertogetherthanwarm pressure istheweightofmoleculesinalargemass 7 this lesson,reread thestatements to seeifyou have changedyour mind. if you agree withthestatement oraDifyou disagree. After you’ve read whether you agree ordisagree withthem.Place anAintheBefore column What doyou think? . i n eoeSaeetAfter Statement Before d d A A Weather isoftenassociatedwithpressuresystems.Air

7 high- low-pressure system 4. 3. There are nosafety precautions for , suchastornadoes andhurricanes. masses. air of large occurs often attheboundaries Readthetwo statements below anddecide isalarge bodyofcirculating airwithlow isalarge bodyofcirculating airwithhigh . Air moves . Airmoves . Airon of pressure systems.of pressure you read the description. graphic withyour fingerafter Trace thedetailsoneach understand whatyou’ve read. and graphs canhelpyou Maps, diagrams, charts, Learning withGraphics • • • • Key Concepts otat contrast 1. Compare and of severe weather? What are someexamples patterns? understand weather Why isitusefulto patterns? What drives weather pressure systems? of What are twotypes 3TUDY#OACH Key Concept Check two types two types CHAPTER 13 LESSON 2

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0 1 / 9 1 / Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 22/19/10 3:08:44 PM polar Maritime are responsible are responsible tropical Maritime Cool, humid Warm, humid tropical Maritime row? Air masses row? Air . An forms when a large, mass forms when . An air polar hot Dry, tropical Continental Continental are large bodies of air with distinct of air with distinct bodies temperature large are Air Mass Classifications Warm, humid Cool, humid tropical Maritime Air masses Air polar Maritime moisture characteristics moisture The figure below identifies types of air masses and the The figure below identifies types Have you ever noticed that the weather sometimes stays sometimes stays that the weather ever noticed Have you can high- and low-pressure systems, Air masses, like extend for a thousand kilometers or more. Sometimes one kilometers or more. Sometimes extend for a thousand masses affect most of the United States. Air air mass covers weather patterns. the same for several days in a for several days the same for this. and The for several days. over an area system stays high-pressure system comes in contact in the high-pressure air circulating moisture and air takes on the temperature with . This the surface below it. characteristics of Air Mass Classification Air Air Masses Air continental air masses. Air masses that form over water are continental air masses. Air masses masses that form near the called maritime air masses. Air Those air masses that equator are called tropical air masses. polar air masses. Air masses form in cold regions are called air and antarctic arctic that form near the poles are called masses. regions where they form. The arrows on the map show the regions where they form. The Air commonly follow. general paths that the air masses and moisture masses are classified by their temperature form over land are called characteristics. Air masses that

Masses

Tropical Air Tropical 8

Where doesWhere d d n Masses i . Polar Air Polar 7 0 4 9 8 8 _

2 Masses L

Visual Visual Check Arctic Air Arctic _ Weather Weather Essentials Reading E R _ 4 continental polar air comecontinental from? 216

2. Classify from a sheet of paper and a sheet from about information record types of air masses. Make a three-columnbook 1 0 _ 7 0 0 _ 3 7 1 CC173_007_014_RE_L2_889407.indd 8 CC173_007_014_RE_L2_889407.indd 9 1 7 3 _ 0 0 7 _ 0 1 4 _ R E

_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 2 _ 8 8 9 4 0 in summer. Inwinter, theycanbringheavysnowfall. They bringhot,humidairtothesoutheasternUnitedStates Ocean. Maritimetropicalairmassesaremoistmasses. Gulf ofMexico,theCaribbeanSea,andeasternPacific form onlyduringsummer. high .Continentaltropicalairmassesusually airmassesbringclearskiesand masses. Thesehotanddry tropics overdry, desertlandarecontinentaltropicalair Alaska andCanada. Polar airmassesthataffectNorthAmericaoftenformover temperatures inwinterandcoolsummer. Continental polarairmassesarefastmoving.Theybringcold over landaredrierthanairmassesthatformoceans. moisture totheairasoceanscan.Thus,massesthatform and warm. aircanmoveoverwater andbecomemoist cool. Cold,dry ocean. Warm, moistaircanloseitsmoistureandbecome to During thewinter, anarctic airmasscanbringtemperatures the Arctic. air. Theseairmassescontainbitterlycold,dry edn setas ete Weather Reading Essentials Fronts Maritime Tropical Air Masses Continental Tropical Air Masses Maritime Polar Air Masses Continental Polar Air Masses AirArctic Masses common atfronts. temperature, , , wind,andprecipitationare Major weatherchangesoftenoccuratfronts.Changesin the airmasswilleventuallybumpintoanothermass. wind carriesanairmassawayfromtheareawhereitformed, armies. boundary. used theword occur attheboundariesbetweendifferentairmasses.He weather. Bjerknesnoticedthatspecifictypesofweather coworkers developedanewmethodforforecastingthe polar airmassesoftenbringcloudy, rainyweather. masses. Theseairmassesarecoldandhumid.Maritime northern AtlanticandPacificOceansaremaritimepolarair 7 . i n d - d Air massescanchangeastheymoveoverthelandand A military front is the boundary betweenopposing frontistheboundary A military JacobBjerknes(BYURKnuhs)andhis In 1918,Norwegian

40°C. 9 A weather front, front Arctic airmassesformoverSiberiaand a military term,todescribethis amilitary is the boundary between two airmasses. two between is theboundary Airmassesthatformoverthe Land cannot transfer as much Landcannottransferasmuch Theseairmassesformoverthe Airmassesforminginthe As weather patterns? equation: use this units to Celsius ( To convert Fahrenheit ( 4. Describe b. a. Conversions 3. b. a.

Example: Covert 76°Fto °C. this equation: to Fahrenheit (°F)units, use To units convert Celsius (°C) Math Skills Convert 86°Fto °C. the Always perform Convert 37°Cto °F. Divide theanswer from first. operation inparentheses Step aby 1.8. °F (76°F Key Concept Check ° = C _____

(44°F) (°C 1.8 = -

______( 32 ° ×

F = 1.8 1.8) - What drives 24°C ° = 32) C) units, C)

44°F) +

32 ° F) 217 22/19/10 3:08:48PM / 1 9 / 1 0

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0 1 / 9 1 / Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 22/19/10 3:08:53 PM Cool air Cool Cold air Cold Warm air Warm Warm Cold air Cold Warm air Warm Warm air Warm Warm air Warm n addition to cold fronts and warm fronts, n addition to cold fronts and warm I The figure below on the left shows a cold front. A cold A a cold front. shows the left on figure below The warm front right shows a warm front. A The figure on the Cold air Cold Cold air Cold forms when less dense, warmer air moves toward colder, colder, dense, warmer air moves toward forms when less mass. When air rises above the cold air The warm denser air. condenses, a wide blanket ofthe water vapor in the warm air bring steady or forclouds forms. These clouds often brings warmerseveral hours or days. A warm front to shift directions. temperatures and causes the wind front forms when a colder air mass moves toward a warmer air toward a warmer air mass moves when a colder front forms cold airAs a result, the than warm air. air is denser mass. Cold and The warm air rises warm air mass. the pushes underneath and clouds the air condenses, vapor in cool. Water begins to along cold and often form form. Rain showers The wind for temperatures to decrease. fronts. It is common cases, cold changes direction. In many becomes gusty and severe storms. fronts give rise to Stationary and Occluded Fronts Stationary and Occluded Warm Fronts Warm Cold Fronts Cold have identified stationary and occluded fronts. These fronts two types of fronts are illustrated below and described on the next page. 0 1 Highlight the

the difference the difference

What types of d d n i . 7 0 4 9 8 8 _ 2 Reading Check L Visual Check Visual Visual Visual Check _ Weather Weather Essentials Reading E R _ 4 between a cold front and a front a cold between warm front. 218 7. Contrast 7. Contrast

6. Describe 6. Describe figures. How is the location of How figures. in the two warm air different types of fronts? label “Warm air” in both of the air” “Warm label

5. Specify with associated are weather fronts? cold 1 0 _ 7 0 0 _ 3 7 1 CC173_007_014_RE_L2_889407.indd 10 CC173_007_014_RE_L2_889407.indd 11 1 7 3 _ 0 0 7 _ 0 1 4 _ R E

_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 2 _ 8 8 9 4 0 fronts usuallybringprecipitation. warm front,anoccluded,orblocked,frontforms.Occluded When afast-movingcoldfrontcatchesupwithslow-moving edn setas ete Weather Reading Essentials Thunderstorms Severe Weather Occluded Front fronts. stationary front. Cloudyskiesandlightrainarecommonalong between twoairmassesstalls,thefrontiscalledastationary front andcoldairontheotherside.Whenboundary stops, forseveraldays.Warm airislocatedononesideofthe FrontStationary expansion andcontractionsoftheairmolecules. and thencontract.Thunderisthesoundmadebyrapid from thelightningcausesairmoleculestorapidlyexpand ground, orgroundtocloud.Theextremethermalenergy canheatthenearbyairtomorethan27,000°C. electricity. Thiselectricityisseenasaboltoflightning. and thechargesofparticlesongroundcreates difference betweenthechargesofparticlesincloud positively andnegativelychargedparticlesinthecloud.The tocrashintoeachother.tiny icecrystals Thiscreates lightning stops,andprecipitationweakens. In thedissipationstage,updraftsstop,windsdiedown, mature stage,thethunderstormbeginstofade,ordissipate. rain, andlightning down towardtheg to appear. Downdraftsareaircurrentsthatmovevertically After thecumuluscloudhasbeencreated,downdraftsbegin are air currentsthatmoveverticallyupfromtheground. cumulus stage,cloudsformandupdraftsoccur. Updrafts in as little30minutes. a cumulus cloudcangrowintoa10-km-tallthundercloud conditions. Thunderstormscanformquickly. Forexample, moisture, andrisingair. Alow-pressuresystembringsthese of theirlightning.Thunderstormshavewarmtemperatures, tornadoes, hurricanes,andblizzards. death. Types ofsevereweatherincludethunderstorms, 7 . i n d d Thunderstorms are also known as electrical storms because Thunderstorms arealsoknownaselectricalstormsbecause Severe weathercancausemajordamage,injuries,and Lightning canmovefromcloudtocloud, Strong updraftsanddowndraftsinathunderstormcause A typicalthunderstormhasthreestages.Duringthe

1 1 Cold fronts move faster than warm fronts. Coldfrontsmovefasterthanwarmfronts. Sometimes an approaching front stalls, or Sometimesanapproachingfrontstalls,or round. Inthematurestage,heavywinds, occur. Within 30minutesofreachingthe answer.) down? (Circle thecorrect itto begin toexpect die of thethunderstorm canyou known asthunder? known lightning to makethesound molecules intheairnear c. c. b. a. 9. Identify 8. Interpret 10. Apply fronts? patterns associated with useful to understandweather the dissipationstage the cumulusstage the mature stage Raig Check Reading Key Concept Check What causes At whichstage Why isit 219 22/19/10 3:08:57PM / 1 9 / 1 0

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0 1 / 9 1 / Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 22/19/10 3:09:03 PM . A A forms when A tornado forms Dr. Ted Fujita developed a system for Fujita developed a system Ted Dr. central United States. This area has been central United States. This area More tornadoes occur in the United States More tornadoes occur in the United is a violent, whirling column of air in contact with the with the air in contact of column whirling is a violent, is an intense tropical storm with exceeding 119 km/h storm with winds exceeding is an intense tropical . Most tornadoes have a diameter of several hundred hundred a diameter of several have . Most tornadoes tornado km/h. The strong, swirling wind in a tornado can send swirling wind in a tornado km/h. The strong, Hurricanes are the most destructive storms on Earth. Hurricanes, like tornadoes, have strong, swirling winds. A A more than tornado can reach speeds within a Wind hurricane is much larger than a tornado. A typical hurricane hurricane is is 480 km across, more than 150 thousand times larger than hurricane is the eye. The eye is a tornado. At the center of a an area of clear skies and light winds. hurricane Hurricanes typically form in late summer over warm, tropical ocean water. ground in than 1,500 m are more The largest tornadoes meters. diameter. 400 Most tornadoes houses flying through the air. cars, trees, and ones, however, minutes. The more destructive last only a few hours. can last for several named Tornado Alley. It extends from Nebraska to Texas. In to Texas. It extends from Nebraska Alley. named Tornado from Canada cold air blowing southward Alley, Tornado air moving northward from often bumps into warm, moist are ideal for severe the Gulf of Mexico. These conditions thunderstorms and tornadoes. than anywhere else on Earth. The most tornadoes occur in than anywhere else on Earth. The an area in the Hurricanes Classifying Tornadoes Formation of Tornadoes of Formation Alley Tornado Tornadoes tormadoes cause moderate to devastating damage. F5 tormadoes cause moderate to devastating tornadoes cause incredible damage. Concrete and steel buildings can be destroyed. F5 can pull bark from trees. classifying the strength of tornadoes. Tornadoes are classified Tornadoes classifying the strength of tornadoes. on the damage they cause. on the Fujita intensity scale based Damage might include F0 tornadoes cause little damage. billboards. F1 through F4 broken tree branches and damaged updrafts begin to rotate. Swirling winds spiral downward to rotate. Swirling winds spiral updrafts begin a funnel the thunderstorm. This creates from the base of it becomes funnel reaches the ground, . When the air is invisible. The funnel cloud you see tornado. Swirling a the tornado. is the dirt and debris lifted by

2 How do How 1

huracan, Would you you Would d d n i . RIGIN 7 0 4 9 O 8 8 _ 2 Reading Check L _ Weather Weather Essentials Reading E ORD R _ hurricane from Spanish means “tempest” 4 220 W 12. Apply

11. Explain tornadoes form? tornadoes expect to F4 tornado an damage or less cause more damage than an F3 tornado? 1 0 _ 7 0 0 _ 3 7 1 CC173_007_014_RE_L2_889407.indd 12 CC173_007_014_RE_L2_889407.indd 13 1 7 3 _ 0 0 7 _ 0 1 4 _ R E

_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 2 _ 8 8 9 4 0 edn setas ete Weather Reading Essentials Severe WeatherSafety Winter Storms and fingerscovered,limityourtimeoutdoors. temperatures arebelow water, highplaces,andtreesthatstandalone.Whenwind-chill objects andelectricalcords.Ifyouareoutside,stayawayfrom is importantandcouldsaveyourlife. already occurring.Payingattentiontowatchesandwarnings weather ispossible.Awarningmeansthatsevere warnings forsevereweather. Awatchmeansthatsevere person’s bodytemperatureislowered. (hi poh THERmeeuh),adangerouscondition inwhicha loss ofbodyheatcanresultinfrostbiteandhypothermia and coldtemperaturescanrapidlycoolexposedskin.The can reducevisibilitytoafewmetersorless.Strongwinds temperatures, strong winds, andblowing snow The weightoftheicecanbreaktreesandpowerlines. storms coattheground,trees,andbuildingswithalayerofice. to freezing(0°C),raincanfreezewhenithitstheground.Ice a typhoon.InAustralia,itiscalledtropicalcyclone. loses energyanddiesout.InAsia,thistypeofstormiscalled areas. Onceahurricanemovesoverlandorcolderwater, it contribute tofloodingthatcandamageordestroyentire areas. Asahurricanecrossesthecoastline,strongrains flooding. Hurricanescreatehighwavesthatcanfloodcoastal from hurricanesoccursastheresultofstrongwindsand 7 Hurricane FormationHurricane . pressure over theocean. air creates anarea oflow clouds form. More rising vapor condenses and air rises, itcools. Water Warm, moistairrises. As 1. Low-Pressure Area i n Low pressure d d The figureaboveshowshowahurricaneforms.Damage During thunderstorms, stay inside and away from metal During thunderstorms,stayinsideandawayfrommetal The U.S.NationalWeather issueswatchesand Service A Winter weathercanbesevere.Whentemperaturesareclose

1 blizzard 3 isaviolentwinterstormcharacterized by freezing - winds of37–62km/h. tropical depression with The storm becomes a center begins to rotate. pressure inthecenter. The Air moves toward thelow 2. TropicalDepression 20°C, dress in layers, keep your head 20°C, dressinlayers,keepyourhead . Theblowingsnow thunderstorms. storm produces strong of more than63km/h. The a tropical storm withwinds rotate. The storm buildsto Air continues to riseand 3. TropicalStorm examples ofsevere weather? 14. Summarize Identify 13. hurricanes form? Visual Check hurricanes. tropical stor Only onepercent of becomes ahurricane. thestorm km/h, Wh 4. Hurricane Key Concept Check en windsexceed 119 How do How do ms become Eye What are 221 22/19/10 3:09:06PM / 1 9 / 1 0

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0 1 / 9 1 / Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 22/19/10 3:09:11 PM END OF LESSON a large body of circulating air with body of circulating a large ED an intense tropical storm with winds exceeding exceeding with winds storm tropical an intense a violent, whirling column of air in contact with whirling column a violent, onnect C low pressure at the center and higher pressure outside and higher pressure the center at pressure low of the system the ground 119 km/h Log on to ConnectED.mcgraw-hill.com ConnectED.mcgraw-hill.com on to Log find this to textbook your and access resources. lesson’s hurricane: system: low-pressure tornado: a large body of circulating air with high body of circulating a large 4 1

d d n i . 7 0 a large body of air with distinct temperature and body of air with distincta large temperature a violent winter storm characterized by freezing freezing by characterized storm winter a violent 4 9 8 8 a boundary air masses two between _ 2 L pressure at its center and lower pressure outside of the system pressure and lower its center at pressure moisture characteristics moisture temperatures, strong winds, and blowing snow blowing and winds, strong temperatures, _ Weather Weather Essentials Reading E Describe how tracing the details on a graphic helped you better understand one of the Describe how tracing the details on a graphic helped you better processes described in this lesson. continental tropical arctic maritime polar the chart about air masses. Use the terms below to complete maritime arctic continental polar maritime tropical Review the terms and their definitions in the Mini Glossary. Write a sentence that Write Mini Glossary. and their definitions in the Review the terms air mass and a front are related. explains how an agree with the statement or a D if you disagree. disagree. or a D if you the statement with agree mind? change your Did you Reread the statements at the beginning of the at the beginning the statements Reread with an A if you column in the After lesson. Fill R What do you think cold landcold areasthe coldest water ocean cold (d) (c) (e) air masses. air masses. air masses. Air masses that form over . . . over form masses that Air waterwarm ocean . . . are warm land (a) (b) air masses. air masses. _ 4 222 3. 2. 1. front: high-pressure system: Mini Glossary air mass: blizzard: 1 0 _ 7 0 0 _ 3 7 1 CC173_007_014_RE_L2_889407.indd 14 Name Date Class

Content Vocabulary LESSON 2 Weather Patterns Directions: Explain the differences between/among each set of terms on the lines provided. You must include the terms below in your answer.

1. high-pressure system, low-pressure system

2. tornado, hurricane

3. blizzard, winter storm

Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.

4. air mass, front

5. thunderstorm, dominate, dissipate

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Lesson Outline LESSON 2 Weather Patterns

A. Pressure Systems 1. A(n) is a large body of circulating air that has low pressure at its center and higher pressure on the outside. a. Air moves from pressure to low pressure. b. In a low-pressure system, air moves away from the of the system. c. Air in the center of the system , and the water vapor in it condenses and forms clouds. 2. A(n) is a large body of circulating air that has high pressure at its center and lower pressure on the outside. a. High-pressure air at the center and moves toward low-pressure areas. b. High-pressure systems bring skies. B. Air Masses 1. are large bodies of air that have distinct temperature and moisture characteristics. 2. An air mass forms when a(n) system lingers in one area for a few days. a. Continental polar air masses are and . b. air masses are warm and humid. c. air masses are very cold and dry. They form over or arctic ice. C. Fronts 1. A weather is the boundary between two air masses. 2. A(n) front forms when a colder air mass moves toward a warmer air mass. It often brings severe and cooler temperatures. Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. The McGraw-Hill of a division © Glencoe/McGraw-Hill, Copyright 3. A(n) front forms when a warmer air mass moves toward a cooler air mass. a. As the warm air rises, water vapor condenses, and often occurs.

Weather 27

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Lesson Outline continued

b. A warm front brings temperatures and shifting winds. 4. A(n) front forms when the boundary between two air masses stalls. It brings skies and light rain. D. Severe Weather 1. A low-pressure system can provide the warm temperatures, moisture, and rising air needed for a(n) to form. a. The stage of a thunderstorm starts with cloud formation and updrafts. b. The stage of a thunderstorm contains heavy winds, rain, and lightning. c. During the stage of a thunderstorm, wind and rain subside. d. Lightning is caused by oppositely particles in clouds and on the ground. 2. A violent, whirling column of air that contacts the ground is a(n) . a. Tornadoes form when updrafts from thunderstorms begin Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. to . b. is the name for the part of the United States that has the most tornadoes. 3. A(n) is an intense tropical storm with winds exceeding 119 km per hour. a. Hurricanes typically form in late summer over warm, tropical and are the largest type of severe storm. b. When a hurricane moves over land or water, it loses energy. 4. A(n) is a severe winter storm, characterized by freezing temperatures, strong winds, and blowing snow. 5. The U.S. National Weather Service issues a(n) when severe weather is possible. It issues a(n) when severe weather is already occurring.

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