Is the North Atlantic Hurricane Season Getting Longer?

In the 2008 North Atlantic hurricane season, July was anomalously active with four tropical storms, of which two intensified to become hurricanes. The 2007 season experienced an uncommon May storm and an equally uncommon December storm. The 2005 season was the most active in the secular record, and was also anomalously active during the typically quiescent early and late portions of the season. This recent increase in early- and late-season activity has raised questions about the effect that climate change may be having on the length of the hurricane season. Here I report on the observed trends in the annual distribution of North Atlantic tropical storm formation events and their relationship with tropical Atlantic sea surface temperatures (SST). I find an apparent tendency toward more common early- and late-season storms that correlates with warming SST, but the uncertainty in these relationships is high.

Kossin, J. P. (2008), Is the North Atlantic hurricane season getting longer? Geophys. Res. Lett., 35, L23705, doi:10.1029/2008GL036012