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Thiswebsitewouldliketoremindyou:Yourbrowser(AppleSafari4)isoutofdate.Updateyourbrowserformore security,comfortandthebestexperienceonthissite. × EncyclopedicEntry stormsurge Forthecompleteencyclopedicentrywithmediaresources,visit: http://education.nationalgeographic.com/encyclopedia/storm-surge/ Astormsurgeisariseinsealevelthatoccursduringtropicalcyclones,intensestormsalsoknownastyphoonsor hurricanes.Thestormsproducestrongwindsthatpushthewaterintoshore,whichcanleadtoflooding.This makesstormsurgesverydangerousforcoastalregions. Tropicalcyclonesarecircularstormscharacterizedbyhighwindsandheavyrainfall.Theyformoverwarm,tropical oceans.Thecenterofacycloneiscalledtheeye.Theeyeissurroundedbyaringofcloudscalledtheeyewall, wherethewindsarestrongest.Surroundingtheeyewallarecloudsthatspiraloutward,calledspiralingrainbands. Astormsurgeisprimarilycausedbytherelationshipbetweenthewindsandtheocean’ssurface.Thewaterlevel riseswherethewindsarestrongest.Inaddition,waterispushedinthedirectionthewindsareblowing.The rotationoftheEarthcauseswindstomovetowardtherightintheNorthernHemisphereandtowardtheleftinthe SouthernHemisphere—aphenomenonknownastheCorioliseffect.IfacyclonedevelopsintheNorthern Hemisphere,thesurgewillbelargestintheright-forwardpartofthestorm.IntheSouthernHemisphere,thesurge willbelargestintheleft-forwardpartofthecyclone. Anotherfactorcontributingtostormsurgeisatmosphericpressure.Atmosphericpressureistheforceexertedby theweightofairintheEarth’satmosphere.Thepressureishigherattheedgesofacyclonethanitisatthecenter. Thispushesdownthewaterintheouterpartsofthestorm,causingthewatertobulgeattheeyeandeyewall— wherethewindshavehelpedaddtotheriseinsealevel. Morefactorscontributetothestrengthofastormsurgeasthedomeofwatercomesashore.Thewaterlevelcan reachashighas10meters(33feet)ifthestormsurgehappensatthesametimeashightide.Theslopeofthe landjustoffthecoastalsoplaysapart:Waterwillmoreeasilyfloodashallowcoastthanasteepone. StormSurgesandCoastalCommunities Tropicalcyclones,andthestormsurgestheygenerate,areaserioushazardforcoastalareasintropicaland subtropicalregionsoftheworld.Developinginthelatesummermonths(July-AugustintheNorthernHemisphere, January-FebruaryintheSouthernHemisphere),whenthewatersarewarmest,tropicalcycloneshitregionsasfar apartastheGulfCoastoftheUnitedStates,northwesternAustraliaandBangladesh. Whenacyclonehitsland,theaccompanyingstormsurgewillmostoftenfloodthesurroundingcoastalarea. Floodingisresponsibleformostdeathsandeconomicdamageassociatedwithtropicalcyclonelandfalls.Whena hurricanehitGalveston,Texas,in1900,thestormsurgewasresponsibleforapproximately6,000deaths.InEast Pakistan(nowBangladesh),theBholacyclonekilledasmanyas500,000peoplein1970.Thestormsurgefrom theBholacyclonewasestimatedtobe10meters(33feet)high. 1of5 Improvementsinforecastingcyclonesandissuingearlywarningstothepublichavebecomeindispensableasboth coastalpopulationsandtheoccurrenceofextremestormscontinuetorise. However,evensophisticatedmeteorologyandstormwarningsdonotalwaysprotectagainstdevastatingstorm surges.HurricaneKatrina’sstormsurgefloodedtheU.S.coastalcommunitiesofLouisianaandMississippi,aswell astheurbanareasofNewOrleans,Louisiana,andBiloxi,Mississippi,in2005.Thefloodingkilledmorethan1,500 peopleinNewOrleansalone,andcausedmillionsofdollarsindamage.Homes,businesses,schools,and hospitalsweredestroyed. Still,improvementsinforecastinggreatlybenefitregionsliketheChesapeakeBay,intheU.S.statesofMaryland andVirginia.TheChesapeakeBaysufferedseveredamagefromHurricaneIsabelin2003.Emergencymanagers failedtopredictIsabel’sextremestormsurges,whichcausedwidespreadfloodingintheregion. Now,meteorologistsandemergencymanagersmonitorthestormsforminginthesoutheastmoreclosely.New computersimulationsbytheFederalEmergencyManagementAgency(FEMA)examinedtheeffectsofaCategory 4hurricane(131-155mphwinds)landingintheU.S.statesofNorthorSouthCarolina,hundredsofmilessouthof theChesapeake.Thesimulationshowedthehurricanecouldproducestormsurgesashighas5or6meters(18or 20feet)alongtheChesapeakeshoreline.FEMAusedthelatestversionofitscomputerizedSLOSHmodelto predictthesurge.Anacronymfor"Sea,Lake,andOverlandSurgesfromHurricanes,''theSLOSHprogramisused bytheNationalWeatherServiceandtheNationalHurricaneCenter. TheMarylandEmergencyManagementAgencyisnowworkingwiththeU.S.ArmyCorpsofEngineersandlocal officialstoturntheSLOSHsimulationdataintoupdatedmapsforemergencyplanning.Thenewmapsshowhow farinlandfloodingcouldstretchundercertainconditions.Withthisnewforecastingdata,emergencyplannersand citizenswillbebetterpreparedforstormsurges. Governmentagenciescanarrangeforresidentstoevacuate.Someresidentsdon’thavecarsandmayrequire transportationtosaferground.Othersmaynothaveaplacetogoandrequireemergencyshelter.Manyresidents, suchasthoseinhospitalsandprisons,areespeciallyatrisk. Advancewarningofastrongstormsurgealsoallowshomesandbusinessestopreparefordamage.Business ownerscanrelocateexpensivemachineryortoolstosafeareas,andhomeownerscanboardupwindowsto protectagainststrongfloodsormovefurnitureandothervaluablestoasecondstory. Wetlands Coastalresidentscanreducethedamagedonebyastormsurgebyprotectinglocalwetlands.Wetlands,suchas swamps,estuaries,andmudflats,actasspongesfortropicalcyclones.Asthecyclonemakeslandfall,themarshy landandplantsabsorbthewaterandtheenergyofthestormsurge.Siltandswampvegetationpreventthemost intensepartofthestormsurgefromhittinghomesandbusinesses. EstuariesaresuchanimportantpartofournaturalenvironmentthattheU.S.EnvironmentalProtectionAgency (EPA)createdtheNationalEstuaryProgramin1987.Thisprogramseekstoimprovethequalityofestuariesto protectimportantwildlifehabitats,publicwatersupplies,andcoastalregionsaffectedbyseverestorms. Thedevelopmentofcoastalwetlandsforhousing,industry,oragriculturereducesthenaturalbarrierthatwetlands provide.Communitiescanprotectthemselvesagainststormsurgesbymaintaininghealthycoastalwetland ecosystems. VOCABULARY 2of5 Term PartofSpeech Definition accompany verb tojoinwithsomeoneorsomething. adversely adverb negativelyorinabadway. agriculture noun theartandscienceofcultivatingthelandforgrowingcrops(farming)orraising livestock(ranching). ArmyCorpsof Engineers noun governmentorganizationconcernedwithconstructionprojects. atmosphere noun layersofgasessurroundingaplanetorothercelestialbody. atmospheric pressure noun forceperunitareaexertedbythemassoftheatmosphereasgravitypullsitto Earth. Bholacyclone noun (1970)stormthatcausedwidespreaddamageanddeathinBangladeshand India. Carolinas noun theU.S.statesofNorthCarolinaandSouthCarolina. Chesapeake Bay noun large,shallowestuaryoftheSusquehannaandotherriversthatflowthroughthe U.S.statesofMaryland,Virginia,WestVirginia,Delaware,Pennsylvania,andNew YorkandthecapitalofWashington,D.C.,beforeemptyingintheAtlanticOcean. Corioliseffect noun theresultofEarth'srotationonweatherpatternsandoceancurrents.TheCoriolis effectmakesstormsswirlclockwiseintheSouthernhemisphereand counterclockwiseintheNorthernHemisphere. cyclone noun weathersystemthatrotatesaroundacenteroflowpressureandincludes thunderstormsandrain.Usually,hurricanesrefertocyclonesthatformoverthe AtlanticOcean. data pluralnoun (singular:datum)informationcollectedduringascientificstudy. economic adjective havingtodowithmoney. ecosystem noun communityandinteractionsoflivingandnonlivingthingsinanarea. Environmental Protection Agency(EPA) noun U.S.governmentorganizationwhosemissionisto"protecthumanhealthandthe environment." estuary noun mouthofariverwheretheriver'scurrentmeetsthesea'stide. evacuate verb toleaveorremovefromadangerousplace. exert verb toforceorpressure. expensive adjective verycostly. eye noun centerofatropicalcyclone,characterizedbyaroughlycircularareaoflightwinds andrain-freeskies. eyewall noun ringofthunderstormsthatsurroundsahurricane'seye. Federal Emergency Management Agency(FEMA) noun U.S.HomelandSecurityagencyresponsibleforcoordinatingresponseandaid distributionafternaturalandmanmadedisasters. flood noun overflowofabodyofwaterontoland. forecast verb topredict,especiallytheweather. 3of5 forecast verb topredict,especiallytheweather. generate verb tocreateorbegin. GulfCoast noun landintheUnitedStatessurroundingtheGulfofMexico. habitat noun environmentwhereanorganismlivesthroughouttheyearorforshorterperiodsof time. hazard noun dangerorrisk. hightide noun waterlevelthathasrisenasaresultofthemoon'sgravitationalpullontheEarth. hurricane noun tropicalstormwithwindspeedsofatleast119kilometers(74miles)perhour. Hurricanesarethesamethingastyphoons,butusuallylocatedintheAtlantic Oceanregion. HurricaneIsabel noun (2003)stormthatcauseddamagetotheU.S.statesofSouthCarolina,North Carolina,andVirginia. Hurricane Katrina noun 2005stormthatwasoneofthedeadliestinU.S.history. low-pressure system noun weatherpatterncharacterizedbylowairpressure,usuallyasaresultofwarming. Low-pressuresystemsareoftenassociatedwithstorms. machinery noun mechanicalappliancesortoolsusedinmanufacturing. map noun symbolicrepresentationofselectedcharacteristicsofaplace,usuallydrawnona flatsurface. marsh noun wetlandareausuallycoveredbyashallowlayerofseawaterorfreshwater. meteorologist noun personwhostudiespatternsandchangesinEarth'satmosphere. meteorology noun studyofweatherandatmosphere. mudflat noun arealeftbarebyrecedinglakeortidalwaters. Northern Hemisphere noun halfoftheEarthbetweentheNorthPoleandtheEquator. phenomenon noun anunusualactoroccurrence. precaution noun actiontakentoavoidanegativeoutcomeorevent. sealevel noun baselevelformeasuringelevations.Sealevelisdeterminedbymeasurements takenovera19-yearcycle. shoreline noun beach,orwhereabodyofwatermeetsland. silt noun smallsedimentparticles. simulation noun copyorreenactment. SLOSH noun (Sea,LakeandOverlandSurgesfromHurricanes)modelsimulationprogram usedtodeterminewhichareasmustbeevacuatedduetoastormsurge. sophisticated adjective knowledgeableorcomplex. Southern Hemisphere noun halfoftheEarthbetweentheSouthPoleandtheEquator. storm noun severeweatherindicatingadisturbedstateoftheatmosphereresultingfrom upliftedair. stormsurge noun abnormalriseinsealevelaccompanyingahurricaneorotherintensestorm.Also 4of5 stormsurge noun abnormalriseinsealevelaccompanyingahurricaneorotherintensestorm.Also calledastormtide. subtropical adjective borderingthetropics,justnorthoftheTropicofCancerandsouthoftheTropicof Capricorn. swamp noun landpermanentlysaturatedwithwaterandsometimescoveredwithit. temperature noun degreeofhotnessorcoldnessmeasuredbyathermometerwithanumerical scale. transportation noun movementofpeopleorgoodsfromoneplacetoanother. tropical adjective existinginthetropics,thelatitudesbetweentheTropicofCancerinthenorthand theTropicofCapricorninthesouth. typhoon noun tropicalstormwithwindspeedsofatleast74miles(119kilometers)perhour. Typhoonsarethesamethingashurricanes,butusuallylocatedinthePacificor IndianOceanregion. urbanarea noun developed,denselypopulatedareawheremostinhabitantshavenonagricultural jobs. vegetation noun alltheplantlifeofaspecificplace. watersupply noun amountofavailablefreshwaterfordrinking,hygiene,andindustrialand agriculturaluse. weather noun stateoftheatmosphere,includingtemperature,atmosphericpressure,wind, humidity,precipitation,andcloudiness. wetland noun areaoflandcoveredbyshallowwaterorsaturatedbywater. wind noun movementofair(fromahighpressurezonetoalowpressurezone)causedbythe unevenheatingoftheEarthbythesun. ForFurtherExploration Audio&Video NationalGeographicVideo:StormSurge NationalGeographicChannel:NakedScience—HurricaneSurge Websites NationalHurricaneCenter:StormSurge ©1996–2015NationalGeographicSociety.Allrightsreserved. 5of5