Hurricane Ivan over the Gulf of Mexico in 2004.

Dr. Phil Klotzbach and Dr. William Gray from the Colorado State University have just issued their updated long-range Atlantic Hurricane forecast for 2008 and the U.S. landfall strike probability. Once again, they are calling for a well above-average tropical season and a higher than normal probability of a major hurricane landfall in the United States.

In section 5 of their pdf, Klotzbach and Gray discuss how the current conditions in the Atlantic basin are quite favorable for an active season.

Where is the global warming part of all this? Well, in section 9 of the pdf, Klotzbach and Gray explain that the very large increase in major hurricanes in the Atlantic basin between 1995-2007 was in their opinion primarily a result of the multi-decadal increase in the Atlantic ocean thermohaline circulation (THC) due to changes in ocean salinity and not directly related to global temperature increase.

Klotzbach and Gray feel that we should not read too much into the highly active hurricane seasons of 2004-2005. Even though the activity was unusual, it was within natural bounds of hurricane variation. The authors note that both 2006 and 2007 had slightly below-average and average activity, respectively.

Klotzbach and Gray believe that the Atlantic basin is currently in an active hurricane cycle associated with a strong thermohaline circulation and an active phase of the Atlantic Multidecadal Oscillation (AMO). They expect this active cycle to continue for another decade or two, before we enter a quieter Atlantic major hurricane period.

By the way, it looks like Dr. Gray is in the slow process of passing the entire responsibilities of producing these forecasts over to the younger Dr. Klotzbach. Gray has been starting to focus more of his time arguing against global warming concerns.