Editing Jet stream (section)

===Effects of ENSO===
[[File:El nino north american weather.png|thumb|right|250 px|Impact of [[El Niño]] and [[La Niña]] on North America]]
{{Main|Effects of the El Niño–Southern Oscillation in the United States}}
[[El Niño–Southern Oscillation]] (ENSO) influences the average location of upper-level jet streams, and leads to cyclical variations in precipitation and temperature across North America, as well as affecting [[tropical cyclone]] development across the eastern Pacific and Atlantic basins. Combined with the [[Pacific Decadal Oscillation]], ENSO can also impact cold season rainfall in Europe.<ref>Davide Zanchettin, Stewart W. Franks, Pietro Traverso, and Mario Tomasino. [http://www3.interscience.wiley.com/journal/114802316/abstract On ENSO impacts on European wintertime rainfalls and their modulation by the NAO and the Pacific multi-decadal variability described through the PDO index.]{{dead link|date=February 2019|bot=medic}}{{cbignore|bot=medic}} Retrieved on 13 May 2008.</ref> Changes in ENSO also change the location of the jet stream over South America, which partially affects precipitation distribution over the continent.<ref name="Caio">Caio Augusto dos Santos Coelho and Térico Ambrizzi. [http://www.cptec.inpe.br/~caio/chile2000.pdf 5A.4. Climatological Studies of the Influences of El Niño Southern Oscillation Events in the Precipitation Pattern Over South America During Austral Summer.] {{Webarchive|url=https://web.archive.org/web/20080530032314/http://www.cptec.inpe.br/~caio/chile2000.pdf |date=30 May 2008 }} Retrieved on 13 May 2008.</ref>

====El Niño====
During [[El Niño]] events, increased precipitation is expected in California due to a more southerly, zonal, storm track.<ref>John Monteverdi and Jan Null. [http://tornado.sfsu.edu/geosciences/elnino/elnino.html "WESTERN REGION TECHNICAL ATTACHMENT NO. 97-37 November 21, 1997: El Niño and California Precipitation."] {{Webarchive|url=https://web.archive.org/web/20091227155828/http://tornado.sfsu.edu/geosciences/elnino/elnino.html |date=27 December 2009 }} Retrieved on 28 February 2008.</ref> During the Niño portion of ENSO, increased precipitation falls along the Gulf coast and Southeast due to a stronger than normal, and more southerly, polar jet stream.<ref>[[Climate Prediction Center]]. [http://www.cpc.noaa.gov/products/analysis_monitoring/ensocycle/ensorain.shtml El Niño (ENSO) Related Rainfall Patterns Over the Tropical Pacific.] {{Webarchive|url=https://web.archive.org/web/20100528035733/http://www.cpc.noaa.gov/products/analysis_monitoring/ensocycle/ensorain.shtml |date=28 May 2010 }} Retrieved on 28 February 2008.</ref> Snowfall is greater than average across the southern Rockies and Sierra Nevada mountain range, and is well below normal across the Upper Midwest and Great Lakes states.<ref name="cpc.ncep.noaa.gov">[[Climate Prediction Center]]. [http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/us_impacts/ustp_impacts.shtml ENSO Impacts on United States Winter Precipitation and Temperature.] {{Webarchive|url=https://web.archive.org/web/20080412000000/https://web.archive.org/web/20080412152736/http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/us_impacts/ustp_impacts.shtml |date=12 April 2008 }} Retrieved on 16 April 2008.</ref> The northern tier of the lower 48 exhibits above normal temperatures during the fall and winter, while the Gulf coast experiences below normal temperatures during the winter season.<ref>[[Climate Prediction Center]]. [http://www.cpc.ncep.noaa.gov/products/predictions/threats2/enso/elnino/UStrank/ond.gif Average October–December (3-month) Temperature Rankings During ENSO Events.] {{Webarchive|url=https://web.archive.org/web/20080530032315/http://www.cpc.ncep.noaa.gov/products/predictions/threats2/enso/elnino/UStrank/ond.gif |date=30 May 2008 }} Retrieved on 16 April 2008.</ref><ref>[[Climate Prediction Center]]. [http://www.cpc.ncep.noaa.gov/products/predictions/threats2/enso/elnino/UStrank/djf.gif Average December–February (3-month) Temperature Rankings During ENSO Events.] {{Webarchive|url=https://web.archive.org/web/20080530032314/http://www.cpc.ncep.noaa.gov/products/predictions/threats2/enso/elnino/UStrank/djf.gif |date=30 May 2008 }} Retrieved on 16 April 2008.</ref> The subtropical jet stream across the deep [[tropics]] of the northern hemisphere is enhanced due to increased convection in the equatorial Pacific, which decreases [[tropical cyclogenesis]] within the Atlantic tropics below what is normal, and increases tropical cyclone activity across the eastern Pacific.<ref name="ENSO TC influence FAQ">{{Cite web|url=http://www.cpc.noaa.gov/products/analysis_monitoring/ensostuff/ensofaq.shtml#HURRICANES|publisher=[[Climate Prediction Center]]|format=FAQ|access-date=21 March 2008|title=How do El Niño and La Nina influence the Atlantic and Pacific hurricane seasons?|archive-url=https://web.archive.org/web/20090827143632/http://www.cpc.noaa.gov/products/analysis_monitoring/ensostuff/ensofaq.shtml#HURRICANES|archive-date=27 August 2009|url-status=dead}}</ref> In the southern hemisphere, the subtropical jet stream is displaced equatorward, or north, of its normal position, which diverts frontal systems and thunderstorm complexes from reaching central portions of the continent.<ref name="Caio"/>

====La Niña====
Across North America during [[La Niña]], increased precipitation is diverted into the [[Pacific Northwest]] due to a more northerly storm track and jet stream.<ref>Nathan Mantua. [http://www.ccb.ucar.edu/lanina/report/mantua.html La Niña Impacts in the Pacific Northwest.] {{webarchive|url=https://web.archive.org/web/20071022030057/http://www.ccb.ucar.edu/lanina/report/mantua.html |date=22 October 2007 }} Retrieved on 29 February 2008.</ref> The storm track shifts far enough northward to bring wetter than normal conditions (in the form of increased snowfall) to the Midwestern states, as well as hot and dry summers.<ref>Southeast Climate Consortium. [http://www.agclimate.org/Development/apps/agClimate/controller/perl/agClimate.pl/agClimate.pl?function=climforecast/outlook.html&location=local&type SECC Winter Climate Outlook.] {{webarchive|url=https://web.archive.org/web/20080304212445/http://www.agclimate.org/Development/apps/agClimate/controller/perl/agClimate.pl/agClimate.pl?function=climforecast%2Foutlook.html&location=local&type |date= 4 March 2008 }} Retrieved on 29 February 2008.</ref><ref>[[Reuters]]. [https://www.reuters.com/article/domesticNews/idUSN1619766420070216 La Nina could mean dry summer in Midwest and Plains.] {{Webarchive|url=https://web.archive.org/web/20080421224855/http://www.reuters.com/article/domesticNews/idUSN1619766420070216 |date=21 April 2008 }} Retrieved on 29 February 2008.</ref> Snowfall is above normal across the Pacific Northwest and western Great Lakes.<ref name="cpc.ncep.noaa.gov"/> Across the North Atlantic, the jet stream is stronger than normal, which directs stronger systems with increased precipitation towards Europe.<ref>Paul Simons and Simon de Bruxelles. [http://www.timesonline.co.uk/tol/news/environment/article3200801.ece More rain and more floods as La Niña sweeps across the globe.]{{dead link|date=September 2024|bot=medic}}{{cbignore|bot=medic}} Retrieved on 13 May 2008.</ref>