4:15 PM - 4:30 PM
[ACG34-10] Isentropic Slope Tendency as a Diagnostic for the Evolution of Severe Extratropical Cyclones
Keywords:Severe storms, Baroclinity, Extratropical cyclones, Atmospheric dynamics, Severe weather
With our isentropic slope diagnostic, we demonstrate with two extreme cases that individual storms affect the environmental baroclinity. The chosen storms Dagmar and Nina affected the Northern UK and Western Norway in the winters of 2011-2012 and 2014-2015, respectively. A buildup of the isentropic slope and atmospheric jet over the Atlantic by preceding storms is evident during the days before Dagmar develops and reaches Western Norway. We discuss the buildup of the baroclinicity for both cases as well as the relative contributions to its tendency. In addition, we describe the life cycle of these storms in terms of how the storm changes and uses its environment to attain its intensity. We also compare our diagnostic to more traditional measures, such as baroclinic energy conversion, pinpointing advantages and caveats of our method.