Is a polar vortex to blame for the recent blasts of frigid weather throughout the Upper Midwest and Northeast?<\/p>\n
Headlines throughout the media and Internet this week were enough to send chills through most:\u00a0 \u201cPolar Vortex on Its Way to Colorado,\u201d \u201cPolar Vortex:\u00a0 Great Lakes Almost Fully Frozen,\u201d \u201cPolar Vortex to Once Again Grip Midwest, Northeast,\u201d and \u201cDid Someone Order Another Polar Vortex.\u201d\u00a0 What\u2019s the real story regarding polar vortexes?<\/p>\n
First of all, there\u2019s nothing new or unusual about a polar vortex<\/a>.\u00a0 The term has been around since 1853, and was first used in the scientific literature in 1939.\u00a0 One of several semi-permanent weather systems over the Earth, a polar vortex is a very broad, cyclonic circulation of winds that occurs in the upper atmosphere, generally centered over both poles (North Pole and South Pole).\u00a0 Both hemispheres have a polar vortex, which forms in late fall and generally reaches peak intensity in mid-winter.\u00a0 Polar vortexes occur at high altitudes, being most well-defined in the stratosphere, and occur higher up in the atmosphere than where most weather occurs in the troposphere.\u00a0 Polar vortexes are influenced mainly by wind movement and transfer of heat.\u00a0 In the fall, circumpolar winds<\/a> begin to increase, causing the polar vortex to spin up higher into the stratosphere.\u00a0 In winter, the winds around both poles decrease, causing the air in the vortex to slow and the vortex to quit growing in size.\u00a0 Then, in late winter to early spring, heat and circulation return, causing the vortex to shrink in size.\u00a0 It is during this final stage that fragmentation of the vortex occurs, causing pieces of the polar vortex to be drawn into the lower latitudes.\u00a0 This breakup of the polar vortex generally occurs sometime between mid-March to mid-May, and signifies the transition from winter to spring.<\/p>\n In the case of the January arctic outbreaks<\/a>, \u201c\u2026a large piece of the vortex broke off and was forced well to the south over Ontario and the northern Great Lakes.\u00a0 Contributing to this southward buckling of the jet stream was a pronounced northward diversion of the polar jet stream over the eastern Pacific Ocean and West Coast of the U.S.\u00a0To the east, or downstream of this northward diversion or ridge of high pressure aloft, the polar vortex was forced southward.\u201d\u00a0 So \u201c\u2026instead of cold, Canadian air grazing the northern tier of the U.S., then draining off into the north Atlantic Ocean, the heart of this Arctic air plunged south into the U.S.\u201d\u00a0 Freezing temperatures were felt as far south as south Florida.<\/p>\n While the repeated cold waves we\u2019ve been experiencing this year are record-setting, they\u2019re not unusual or unprecedented, according to The Weather Channel\u2019s Senior Meteorologist Stu Ostro. <\/a>\u201cThere have been others in the past which have been of greater magnitude in a number of ways (such as in 1996, 1994, 1985, 1983, 1977, and farther back in time, perhaps the most extreme one on record, 1899),\u201d says Ostro.\u00a0 What is noticeable, however, is the intensity of the cold, which Ostro says, \u201chas been relatively rare in the past couple decades.\u201d<\/p>\n Ostro also points out that \u201cThis recent cold weather must also be viewed in geographical context.\u00a0 While there have been frigid arctic air masses and major snow\/ice storms the past few weeks in the Lower 48 and Canada, the area of below average temperatures is amidst a large area of warmer-than-average temperatures.\u201d\u00a0 He points out, for example, that in the Southern Hemisphere, especially in Australia and Argentina, the extreme heat has been more climatologically significant than the cold that has been occurring in the Northern Hemisphere.<\/p>\n So what about global warming\u2014has it produced stronger polar vortexes?\u00a0 \u201cGlobal warming did not create polar vortexes, though the changing climate might be changing the nature of them.\u201d\u00a0 He also adds that \u201cThere is increasing evidence that the additional warmth in the atmosphere is leading to a change in nature of weather extremes, possibly including patterns such as ones associated with recent weather in the U.S. and elsewhere.\u201d\u00a0 Case in point, just this week the Agence France-Presse reported that 21,341 birds were killed in France<\/a> by violent winter storms, something that hasn\u2019t occurred since 1900.<\/p>\n March may be \u201ccoming in like a lion\u201d for many parts of the U.S. and the world, but we need to look at the bigger picture for perspective.\u00a0 Climate change may be influencing the nature of polar vortexes, but polar vortexes don\u2019t \u201ccause\u201d Arctic blasts.\u00a0 The atmosphere is much more complicated than that.\u00a0 Maybe the question we need to be asking is how much more extreme can these weather events get?\u00a0 Based on records taken from ice core samples, today\u2019s \u201cextremes\u201d pale in comparison with those of the past.\u00a0 Perhaps we\u2019re just beginning to see the tip of the iceberg.<\/p>\n