Tornado threat increases as Gulf hurricanes get larger
Atlanta (September 8, 2009) —Tornadoes that occur from hurricanes moving inland from the Gulf Coast are increasing in frequency, according to researchers at the Georgia Institute of Technology. This increase seems to reflect the increase in size and frequency among large hurricanes that make landfall from the Gulf of Mexico. The findings can be found in Geophysical Research Letters online and in print in the September 3, 2009 issue. “As the size of landfalling hurricanes from the Gulf of Mexico increases, we’re seeing more tornadoes than we did in the past that can occur up to two days and several hundred miles inland from the landfall location,” said James Belanger, doctoral student in the School of Earth and Atmospheric Sciences at Georgia Tech and lead author of the paper. Currently, it’s well known that when hurricanes hit land, there’s a risk that tornadoes may form in the area. Until now, no one has quantified that risk because observations of tornadoes were too sporadic prior to the installation of the NEXRAD Doppler Radar Network in 1995. Belanger along with co-authors Judith Curry, professor and chair of the School of Earth and Atmospheric Sciences at Tech and research scientist Carlos Hoyos, decided to see if they could create a model using the more reliable tornado record that’s existed since 1995. … The team looked at 127 tropical cyclones from 1948 up to the 2008 hurricane season and went further back to 1920 modifying their model to account for the type of data collected at that time. They found that since 1995 there has been a 35 percent percent increase in the size of tropical cyclones from the Gulf compared to the previous active period of storms from 1948-1964, which has lead to a doubling in the number of tornadoes produced per storm. The number of hurricane-induced tornadoes during the 2004 and 2005 hurricane seasons is unprecedented in the historical record since 1920, according to the model. “The beauty of the model is that not only can we use it to reconstruct the observational record, but we can also use it as a forecasting tool,” said Belanger. …
