Quiet hurricane season is due to varying factors, says RMS

The unusually quiet hurricane season is due to several factors, says RMS senior director Brian Owens.

The phase of El Nino Southern Oscillation (ENSO) is one of the most important factors to consider. It was neutral for the 2013 season, which should have been reasonably favourable for hurricane development.

“The other main factor was that sea surface temperatures over a large part of the Atlantic were cooler than normal. That took away the principal source of energy that helps to drive the genesis and the development of hurricanes,” said Owens.

Dry wind from the Sahara Desert inhibited tropical waves coming off of the coast of Africa and reduced atmospheric instability also put a damper on storm formation.

“It was a combination of factors, really, that helped contribute to the overall lower level of major hurricanes,” added Owens.

2013 is the eighth year in a row without a major hurricane making landfall in the US. Hurricane Wilma in 2005 was the last major hurricane to touch ground on the US coast, the longest stretch without such a storm since the 1860s.

While it’s far too soon to say what 2014’s hurricane season might look like, Owens indicated that the phase of ENSO and Atlantic and Gulf of Mexico sea-surface temperatures would be closely followed by RMS as the season approaches. He said: “During the season we would be watching for things like wind shear and other factors affecting tropical wave development such as Saharan dry air.”

Overall, Owens said: “The 2013 season fits in very much with our research, which finds that during these periods when we’re getting busier hurricane seasons it’s often associated with storms forming further to the east out in the Atlantic. Busy seasons are not necessarily transferring to landfall in the US, and we reflect that research in our model.”