Colorado State scientists predict inactive hurricane season

William Gray announces decision to step down

Colorado State University atmospheric scientists Phil Klotzbach and William Gray have predicted less than average tropical cyclone activity during the 2015 hurricane season, forecasting only seven named storms, three hurricanes and one major hurricane. 

“We anticipate that the 2015 Atlantic basin hurricane season will be one of the least active seasons since the middle of the 20th century,” they said in their forecast report, noting that it was likely that an El Niño of at least moderate strength would develop this summer and fall. El Niño, which is caused by an anomalous warming of the equatorial waters of the central and east central Pacific Ocean, is known to cause increased wind shear in the Atlantic basin, something that inhibits hurricane formation. 

In addition to the likely El Niño, Mr. Klotzbach and Mr. Gray noted that sea surface temperatures in the tropical and subtropical Atlantic Ocean were currently cooler than normal, something which, if it persists during the hurricane season, would also tend to inhibit the formation and strengthening of tropical cyclones. 

Because of the predicted reduced activity during the upcoming hurricane season, the scientists said they also anticipated a below-average probability for major hurricanes making landfall along the U.S. coastline and in the Caribbean. 

“Despite the forecast for below-average activity, coastal residents are reminded that it only takes one hurricane making landfall to make it an active season for them,” the report said. “They should prepare the same for every season, regardless of how much activity is predicted,” 

The 85-year-old Mr. Gray has been associated with the Colorado State Department of Atmospheric Science seasonal hurricane forecasts since 1984. Mr. Klotzbach joined the project in 2000 and became the lead author of the reports in 2006. 

“Phil has been making all the final forecast decision in recent years,” Mr. Gray said in a special note included in Thursday’s report, “He has, nevertheless, appointed me to serve in the important role of taking the blame for any and all forecast busts, with all credit for successful forecasts going to him. I have fully embraced this special arrangement!” 

However, Mr. Gray said that while he still comes to the office every working day and remains quite active, he is now devoting his research efforts to climate change and global warming issues.  

“For this reason, I will be discontinuing my formal association with these seasonal hurricane forecasts at the end of this year,” he said. “But I will remain as a special personal advisor to Phil in all of his CSU hurricane forecasts as long as I am able.” 

Mr. Gray said he expected Mr. Klotzbach to carry on making Colorado State’s seasonal hurricane forecasts “with his ever-improving hurricane-climate understanding and continuous forecast skill improvement.” 

“There is no one, in my view, better able to do this than Phil,” he said. 

This year, however, Mr. Gray will continue to work with Mr. Klotzbach in producing the seasonal updates of the 2015 Atlantic basin hurricane forecast. Additional updates will be issued on June 1, July 1 and Aug. 3, and there will also be two-week forecasts of Atlantic tropical cyclone activity during the climatological peak of the season from August through October. In addition, Colorado State will issue a verification and discussion of all 2015 forecasts in late November 2015. 

Part of the report answers the question about why Colorado State issues the extended-range forecasts, especially when the scientists acknowledge that the Atlantic basin has the largest year-to-year variability of any of the global tropical cyclone basins.  

“People are curious to know how active the upcoming season is likely to be, particularly if you can show hindcast skill improvement over climatology for many past years,” the report states. “Everyone should realize that it is impossible to precisely predict this season’s hurricane activity in early April. 

“There is, however, much curiosity as to how global ocean and atmosphere features are presently arranged as regards to the probability of an active or inactive hurricane season for the coming year. Our new early April statistical forecast methodology shows strong evidence over 29 past years that significant improvement over climatology can be attained.  

“We would never issue a seasonal hurricane forecast unless we had a statistical model developed over a long hindcast period which showed significant skill over climatology.” 

Mr. Gray


Mr. Klotzbach