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Cyclone, Types , Effects and formation of Cyclone
a systemof windsrotatinginwardstoan area of low barometricpressure,withananticlockwise
(northernhemisphere) orclockwise(southernhemisphere) circulation;adepression.
This article is about the meteorological phenomenon. For other uses, see Cyclone (disambiguation).
An extratropical cyclonenearIcelandonSeptember4,2003
In meteorology, a cycloneis an area of closed, circular fluid motion rotating in the same direction as
theEarth. This is usually characterizedby inward spiraling winds that rotate counterclockwise in the Northern
Hemisphere and clockwise in the Southern Hemisphere of the Earth. Most large-scale cyclonic circulations
are centered on areas of low atmospheric pressureThe largest low-pressure systems are cold-core polar
cyclones and extratropical cyclones which lie on the synoptic scale.
Cyclones are defined as ``an atmosphericsysteminwhichthe barometricpressure
diminishesprogressivelytoaminimumatthe centre and towardwhichthe windsblow spirallyinward
fromall sides,resultinginaliftingof the airandeventuallyincloudsandprecipitation...''.Hurricanesare
cyclones,thatoriginate inthe tropicswithwindspeedsbeyond64knots (= 74 mph,113 km/h)
Types of Cyclones
The term 'cyclone' actually refers to several different types of storms. They occur in different places,
and some occur overlandwhile othersoccuroverwater.What theyall have incommonis that theyare
Tropical cyclones: are what mostpeople are familiarwithbecause theseare cyclonesthat
occur overtropical oceanregions.Hurricanesandtyphoonsare actuallytypesof tropical
cyclones,buttheyhave differentnamessothatit'sclear where thatstormis occurring.
Hurricanesare foundinthe AtlanticandNortheastPacific,typhoonsare foundinthe Northwest
Pacific.If youhear 'tropical cyclone,'youshouldassume thatit'soccurringin the SouthPacificor
IndianOcean,butfor thislesson,we'lluse itrefertoall typesof tropical oceancyclones.
We can alsofurtherdescribe tropical cyclonesbasedontheirwindspeeds.Theyare calledcategory1,2,
3, 4 or 5, increasingwithintensityandwindspeedasthe numberincreases.A category1 cyclone isthe
weakest,withwindspeedsof 74-95 mph.A category5 cyclone,onthe otherhand,isextremely
dangerousandhas the potential formajordamage.Category5 cycloneshave windspeedsof 155 mph
Polar cyclones: are cyclonesthatoccur inpolarregionslike Greenland,Siberiaand
Antarctica.Unlike tropical cyclones,polarcyclones are usuallystrongerinwintermonths.Asyou
can see,these stormsreallydopreferthe colderweather!Theyalsooccurinareas that aren't
verypopulated,soanydamage theydois usuallyprettyminimal.
A mesocyclone: is whenpartof a thunderstormcloudstartsto spin,whichmayeventually
leadto a tornado.'Meso' means'middle',soyoucan thinkof thisas the mid-pointbetweenone
type of storm and the other.Tornadoesall come fromthunderstormclouds,butnotall
thunderstormcloudsmake tornadoes.Inorderfora tornadoto occur, part of that cloudhas to
spin,andthoughyou can't reallysee thishappening,thisisthe intermediate,or'meso'step
fromregularcloudto dangerousspinningcloudrunningalongthe ground.
Formation of a Cyclone:
Eventhoughtheyformoverdifferentareas,cyclonestendtocome aboutinthe same wayand revolve
aroundthat low-pressureeye.Warmairlikestorise,andas itrises,itcools.Cool air can't holdas much
moisture aswarm air,so that watergetssqueezedoutof the condensingairanda cloudbeginstoform.
If the warmair risesveryquickly,thiscreatesan updraft.
Likewise,if the waterinthe cloudbuildsupenough,itmayfall back to the groundas rain and drawcool
air downwithitas a downdraft. Whentheyworktogether,thatwarm updraftandcool downdraft
create a storm cell.As thisprocesscontinues,the cloudgrowsandwe eventuallygetalarge
Thisthunderstormcloudisnowreadyto diversifyintootherstormslike tropical cyclonesandtornadoes.
But thiscan't happenunlessthe airinthe cloud startsspinninghorizontally.If thisoccursoverthe
tropical ocean,thisiscalleda tropical depression.Thisislike ababy tropical cyclone,withwindspeeds
If it starts spinningevenfasterandhaswindspeedsbetween40-73mph,we have a tropical storm. If
the storm growsevenlargeroverthe tropical oceanand haswindspeedsabove 74 mph,we have our
full-grownhurricane,typhoonorcyclone,depending onwhere thatstormisfound.
If the spinningoccursoverland,we nowhave ourmesocyclone.If the mesocyclone getsspinningfast
enoughthatthe cloudstartsreachingtowardthe groundlike alongarm, thisisthe beginningof a
tornado.If the cloud'sarm reachesall the wayto the groundand grabshold,thisisnow officiallya
tornado,readyto suck upeverythinginitspathlike agiantvacuum cleanerhose.
Effects of Cyclones and Hurricanes:
i. Tropical cyclones cause heavy rainfall and landslides.
ii. They cause a lot of harm to towns and villages, causing severe damage to kuccha
houses. Coastal businesses like shipyards and oil wells are destroyed.
iii. They harm the ecosystem of the surrounding region.
iv. Civic facilities are disturbed.
v. Agricultural land is severely affected, especially in terms of water supply and soil
vi. It causes harm to human, plant and animal life.
vii. Communication systems are badly affected due to cyclones.
Management and Mitigation of Cyclones and Hurricanes:
i. Coastal areas should be well prepared to meet eventualities that arise from cyclones.
ii. Houses should be constructed such that they can withstand the heavy rainfall and
iii. Shelter beds should be created to check soil erosion and speed of winds.
iv. Remote sensing techniques should be used to forecast cyclones appropriately.
v. When a cyclone does occur, rescue and relief operations should be in place.