Impacts of extratropical transition of Northern Hemisphere available potential energy

The impacts of the extratropical transition (ET) of Hurricane Noel (Oct 31 – Nov 3, 2007) were not confined to coastal sections of North America. In fact, a preliminary analysis of the hemispheric flow indicates that the flow pattern evolved from a wave 1 configuration which resembled a positive phase of the Arctic Oscillation, in the week preceding Noel, to a highly amplified wave 3 configuration in the week following Noel eventually leading to the development of a major mid-latitude cyclone along the western coast of North America nine days later. This flow rearrangement resulted in a decrease in the hemispheric available potential energy (APE) that is only rivaled by the ET of Typhoon Dale (1996). In fact, preliminary results indicate that the vast majority of significant APE collapses during the fall season are associated with ET's in either the North Atlantic or North Pacific Basins. These APE collapses occur in a period where the climatological background indicates a strong increase in APE. However, not all ET's are associated with a strong decrease in APE. Some systems appear to barely impact the mean climatological increase in APE, while others actually result in a rapid increase in APE. It is the goal of this study to diagnose the flow configurations and associated dynamics of ET's with vastly differing impacts on the hemispheric APE.