low pressure area low pressure area low depression region atmospheric pressure lower surrounding locations low pressure systems form areas wind divergence occur upper levels formation process low pressure area known cyclogenesis field atmospheric divergence aloft occurs areas area east upper form half wave trough large extends second area wind divergence aloft occurs ahead embedded smaller winds aloft ahead cause atmospheric lift surface pressures upward motion partially force gravity thermal lows form localized heating caused greater sunshine land masses localized areas warm air dense surroundings warmer air rises atmospheric pressure near portion earth surface large scale thermal lows continents help drive monsoon low pressure areas form organized thunderstorm activity warm water occurs tropics concert known monsoon trough monsoon reach northerly extent august southerly extent february convective low hot circulation tropics termed tropical cyclone tropical cyclones form month year globally occur northern southern hemisphere november atmospheric lift generally produce cloud cover cooling air saturated rises low pressure area typically brings cloudy skies act minimize temperature extremes clouds reflect sunlight incoming solar radiation decreases causes lower temperatures day night effect clouds outgoing radiation heat energy surface allows warmer low temperatures seasons stronger area low pressure stronger winds experienced vicinity globally low pressure systems frequently located lee rocky_mountains europe particularly united_kingdom recurring low pressure weather systems typically known depressions formation cyclogenesis development strengthening cyclonic low pressure areas atmosphere cyclogenesis opposite high pressure system equivalent deals formation high pressure areas cyclogenesis umbrella term different processes result development sort cyclone term cyclone circular pressure systems flow direction earth rotation normally areas low pressure largest low pressure systems cold core polar cyclones extratropical cyclones lie scale warm core cyclones tropical cyclones polar lows lie smaller subtropical cyclones intermediate size cyclogenesis occur scales scale larger scale called waves scale embedded flow larger scale smaller scale nature waves embedded flow waves migrate polar cyclones located northern southern share important aspect upward vertical motion upward motions decrease mass local atmospheric columns air lower surface pressure extratropical cyclones form waves weather fronts passing aloft upper level jet streak later life cycle cold core cyclones polar lows small scale short lived atmospheric low pressure systems found ocean areas main polar northern larger class weather systems polar lows difficult detect conventional weather reports hazard high latitude operations shipping gas oil platforms vigorous systems near surface winds metres second mph tropical cyclones form heat driven significant thunderstorm activity warm core defined certain criteria need met formation situations water temperatures needed depth waters temperature cause atmosphere unstable sustain convection thunderstorms factor rapid cooling height allows release heat powers tropical cyclone high humidity needed especially lower mid great deal moisture atmosphere conditions favorable disturbances develop low amounts wind shear needed high shear storm circulation lastly formative tropical cyclone needs pre existing system disturbed weather circulation cyclonic development place form warm core cyclones land lead tornado formation form develop environments high instability low vertical wind shear lack ground plant moisture normally provide cooling lead intense rapid solar heating lower layers air hot air dense surrounding cooler air combined rising hot air results low pressure area called thermal low monsoon caused thermal lows form large areas land strength driven land heats quicker surrounding nearby ocean creates steady wind blowing land bringing moist near surface air oceans similar rainfall caused moist ocean air lifted upwards mountains surface heating convergence surface divergence aloft storm produced surface lifting occurs air expansion lower pressure turn produces winter land quickly ocean keeps heat longer higher specific heat hot air ocean rises creating low pressure area breeze land ocean large area drying high pressure formed land increased cooling similar sea land term usually referring localized daily cycle circulation near coastlines larger scale stronger seasonal mid latitudes large polar cyclones help determine steering systems moving mid latitudes south arctic north index gauge magnitude effect arctic extratropical cyclones tend form east trough positions aloft near east coast continents west oceans study extratropical cyclones shows 30th parallels average cyclones existence hour period separate study suggests approximately significant extratropical cyclones form winter europe particularly united_kingdom recurring extratropical low pressure weather systems typically known depressions tend bring wet weather year thermal lows occur continental areas summer mexican plateau south_america southeast_asia lows commonly located lee rocky_mountains monsoon trough elongated areas low pressure form monsoon trough convergence zone cell circulation monsoon western pacific reaches latitude late summer surface ridge opposite hemisphere strongest reach far 40th parallel august 20th parallel australia february progression accelerated onset summer monsoon characterized development lower air pressure continents large scale thermal lows continents help create pressure drive monsoon southern hemisphere monsoon trough associated australian monsoon reaches southerly latitude february oriented west northwest east southeast axis world associated low pressure systems tropical cyclone tropical cyclones generally need form 5th parallel north 5th parallel south allowing effect winds blowing low pressure center creating circulation worldwide tropical cyclone activity peaks late summer difference temperatures aloft sea surface temperatures greatest particular basin seasonal patterns worldwide scale active month september active month november month activity tropical cyclone basins possible nearly world tropical cyclones form western pacific ocean making active tropical cyclone basin earth associated weather wind initially accelerated areas high pressure areas low pressure density temperature moisture differences air masses stronger high pressure systems contain cooler drier air air mass flows areas warm moist vicinity low pressure areas advance associated cold fronts stronger pressure difference pressure gradient high pressure system low pressure system stronger wind stronger areas low pressure associated stronger winds force caused earth rotation gives winds low pressure systems counter clockwise circulation northern hemisphere wind moves inward right center high pressure clockwise circulation southern hemisphere wind moves inward left center high pressure friction land wind flowing low pressure systems causes wind flow inward flowing centers low pressure area commonly associated weather high pressure area associated light winds fair skies
Low-pressure area