Wednesday, 25 January 2017: 5:00 PM
Conference Center: Tahoma 3 (Washington State Convention Center )
Observations since the 1940's have shown that the preferential formation zones for the coldest air masses in the Northern Hemisphere are generally located near the Northwest Territories and Yukon of Canada as well as the Siberian regions of Russia. However, considerable inter-annual and decadal variability exists with recent decades (the past 30 years) indicating that the coldest air masses have been more commonly found over northwestern Canada and/or Greenland. The winters of 2013-2104 and 2014-2015 however deviated significantly from climatology in that the coldest air masses consistently formed over Canadian provinces that are east of the usual formation zones, in association with a polar vortex that generally resided in the vicinity of Hudson Bay. In fact, the persistence of the cold pool in the vicinity of Hudson Bay was unprecedented in the 66 year record of the reanalysis. Meanwhile, most of the rest of the Northern Hemisphere was experiencing near record warmth associated with similarly persistent flow regimes. The combination of the persistence of these flow regimes, in conjunction with historic sea-surface temperature anomalies, significantly impacted the cyclogenesis in both basins. these warm pools were situated in regions of significant anomalous cyclonic differential vorticity advection with respect to height, which is favorable for cyclogenesis. Consequently, we will examine the role of the warm pools in enhancing the cyclogenesis in particular and ascent in general through a reduction of the static stability in the lower troposphere. Furthermore, the increase in the water vapor availability in association with increased evaporation over the warm pool will be evaluated with respect to condensational heating and feedbacks onto the upper-level height fields in association with modulating the persistence and amplitude of the trough/ridge couplets in each basin.
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