Editing Arctic oscillation (section)

== Events of 2010 ==

A further, quite graphic illustration of the effects of the negative phase of the oscillation occurred in February 2010. In that month, the Arctic oscillation reached its most negative monthly mean value at about −4.266, in the entire post-1950 era (the period of accurate record-keeping).<ref>{{cite journal |last=Ripesi |first=Patrizio |year=2012 |title=The February 2010 Arctic oscillation Index and its stratospheric connection|journal=Quarterly Journal of the Royal Meteorological Society|volume=138|issue=669 |pages=1961–1969|url=http://clima.meteoam.it/Articoli/Art14.pdf |doi=10.1002/qj.1935|display-authors=etal|bibcode = 2012QJRMS.138.1961R |s2cid=122729063 }}</ref> That month was characterized by three separate historic snowstorms in the [[Mid-Atlantic states|mid-Atlantic region]] of the United States. The [[February 5–6, 2010 North American blizzard|first storm]] precipitated {{convert|25|in}} on [[Baltimore, Maryland]] on February 5–6, and a [[February 9–10, 2010 North American blizzard|second storm]] precipitated {{convert|19.5|in}} on February 9–10. In New York City, a [[February 25–27, 2010 North American blizzard|separate storm]] deposited {{convert|20.9|in}} on February 25–26. 
Another snowstorm swept [[Catalonia]] as well as neighbouring French departments ([[Languedoc-Roussillon]], [[Midi-Pyrenées]]) on March 8, depositing 60&nbsp;cm of snow in [[Girona]].<ref>{{cite journal |last=Llasat |first=M.C. |year=2014 |title=The snow storm of 8 March 2010 in Catalonia (Spain): a paradigmatic wet-snow event with a high societal impact |journal= Natural Hazards and Earth System Sciences |volume=14 |issue=2 |pages=427–441 |url=https://www.nat-hazards-earth-syst-sci.net/14/427/2014/nhess-14-427-2014.pdf |doi=10.5194/nhess-14-427-2014 |bibcode=2014NHESS..14..427L |display-authors=etal|doi-access=free }}</ref> This kind of snowstorm activity is considered to be highly anomalous, and as extreme as the negative Arctic oscillation value itself. These negative values of the AO during 2010 and following into the next winter allowed colder air to penetrate much further south than usual into sub-tropical South Florida which brought record breaking low temperatures and months registered in many locations <ref>{{citation |title=2010 South Florida Weather in Review |url=https://www.weather.gov/media/mfl/news/2010WxSummary.pdf }}</ref> and the coolest average monthly minimum temperatures for February, March and December that year in the tropical beach getaway of [[Cancún]], up to over 4C below the climate period averages.<ref>{{citation |title=SERVICIO METEOROLÓGICO NACIONAL NORMALES CLIMATOLÓGICAS |url=http://smn.cna.gob.mx/climatologia/Normales5110/NORMAL23155.TXT|archive-url=https://web.archive.org/web/20150705224131/http://smn.cna.gob.mx/climatologia/Normales5110/NORMAL23155.TXT|archive-date=2015-07-05}}</ref>

The greatest negative value for the Arctic oscillation since 1950 in January was −3.767 in 1977, which coincided with the coldest mean January temperature in New York City, Washington, D.C., Baltimore, and many other mid-Atlantic locations in that span of time, although the January Arctic oscillation has been negative only 60.6% of the time between 1950 and 2010, nine of the ten coldest Januarys in New York City since 1950 have coincided with negative Arctic oscillations.<ref name="ReferenceA">National Weather Service Climate Prediction Center and NWS Forecast Office, as of 2010</ref>