As hurricane season nears its peak, scientists at the University of Rhode Island continue to improve a hurricane prediction model that’s used by the National Hurricane Center.
Isaac Ginis, a physical oceanographer at URI’s Graduate School of Oceanography, said researchers developed the latest model by better understanding the physics of the interaction between the hurricane and the ocean. Since hurricanes draw their energy from warm ocean water, scientists need to accurately calculate the heat coming from the ocean to predict a hurricane’s intensity and where it will make landfall.
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“We made an improvement of the heat exchange model,” Ginis said. That model is combined with an atmospheric model developed by the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory.
According to Ginis, the combined NOAA and URI model was the most accurate used by storm forecasters.
“Over the past two years, our model was the best prediction model the hurricane center used,” Ginis said. “It’s among dozens of models they use. The intensity and track prediction is about 10 percent better than last year’s.”
Ginis and his team of research scientists and graduate students have been working on these prediction models since 2001, and continue to hone an improved version for the 2006 hurricane season.
“The new system is going to be much improved,” Ginis said. “We’re doing some testing this hurricane season and those ideas will be implemented next season.”
More accurate hurricane predictions means forecasters can narrow the areas under hurricane watches or warnings, thereby saving money by reducing the cost of hurricane preparations, Ginis said.
Ginis was one of the first scientists to show the considerable part the ocean plays in the formation, direction, track and intensity of hurricanes. He said researchers use satellite information from the National Weather Service, planes that fly into storms and ocean buoys.
“We use all the data that’s available to the National Hurricane Center,” Ginis said.
Ginis said the most important piece of information in hurricane prediction is the ocean’s temperature. The storms develop from heat from the ocean.
“Hurricanes typically die when they make landfall because they’re deprived of their energy source,” Ginis said.
Hurricane winds generate ocean currents that prompt the warmer surface waters to mix with cooler subsurface waters. The result of the mixing is a wake of cool water on the surface behind most hurricanes, Ginis said. The cool wake is another important factor in judging the intensity of the storms.
The model has also been improved by studying the boundary between the ocean and the air.
“Surface waves create friction or drag which has the effect of slowing the surface wind in hurricanes,” Ginis said. “We used to think that when stronger winds created higher waves, the drag would increase. But it turns out that’s not true. When the winds reach 75 miles per hour and higher, the hurricane just seems to skim across the top of the waves and is less impacted by the surface roughness of the waves.”
Because of the improved understanding of the interaction between the hurricane’s winds and the ocean surface, Ginis and his team were able to improve their model. Forecasters anticipate the hybrid model with NOAA will be even more accurate at forecasting very intense hurricanes.
Ginis and his team will be tracking all the hurricanes that form this season in their lab at the Graduate School of Oceanography. They will present their results this winter at a conference of weather forecasters and researchers. The hurricane center will then test the improved model. It is expected to be made operational by May 1.
