Northeast Hurricane Modeling Outdated
July 26, 2014
NARRAGANSETT, R.I. — Hurricanes bound for New England will get about 10 percent more powerful by 2100, but the state lacks the tools to assess their impacts, according to University of Rhode Island professor Isaac Ginis.
Hurricanes are powered by warm water, and the predicted increase in ocean temperatures caused by climate change is expected to make hurricane season longer and the storms stronger in the years ahead.
“Hurricanes love warm water,” Ginis said during a July 24 climate change seminar at the University of Rhode Island.
Numerous studies and models suggest the frequency of category 4 and 5 hurricanes are expected to increase by 81 percent, while the volume of rainfall is expected to increase 20 percent by 2100, Ginis said.
However, a key current modeling method used to measure the impacts of hurricanes and set flood insurance maps is outdated, he said. The federal Hazus model mostly relies on ocean temperatures to predict damage on land. But, Ginis said, this modeling leaves out critical atmospheric factors that hurricanes encounter as they approach New England, such as cold fronts and the jet stream.
These local factors can make hurricanes more powerful as they take on the characteristics of a nor’easter, he said. “That’s why they often gain energy and intensify.”
As hybrid storms, or extra-tropical storms, hurricanes in northern regions produce differences in rainfall, wind speed and height of storm surge.
Earlier this month, Hurricane Arthur was considered benign as it passed to the east of New England, but the storm strengthened as it headed north along the Gulf Stream and encountered new atmospheric conditions. Arthur then inflicted significant damage when it made landfall in Canada’s maritime provinces, with more rain and higher winds than expected.
“We’re lucky the storm did not undergo extra-tropical transition when it was close to Rhode Island,” Ginis said.
Another problem with current hurricane forecasting is the public and media fixation on the 1-5 ranking system assigned to measure hurricane strength, he said. The ranking is primarily based on wind speeds but leaves out other critical factors, such the height of water within a hurricane. Water height determines the storm surge and influences coastal and inland flooding, two factors that caused major damage in hurricanes Sandy and Katrina.
“Scientists and the forecasters hate this scale,” Ginis said. “It really does not represent the threat (from hurricanes).”
As an alternative, the National Hurricane Center is experimenting with detailed real-time models that monitor water height, storm surge and flooding.
Hurricane forecasting and planning, however, used by the Federal Emergency Management Agency (FEMA) and state planners relies on a modeling system called SLOSH (sea, lake and overland surges from hurricanes). SLOSH modeling began in the 1960s and doesn’t take into account atmosheric and geographic factors that are common to the Northeast during hurricanes.
“We do need a more robust threat and risk analysis in Rhode Island,” Ginis said.
In order to create a better hurricane predictor, Ginis is working with URI’s Graduate School of Oceanography on a multi-model system that uses 3-D simulations, as well as climate-change assumptions, such as sea-level rise, to gauge atmospheric and oceanic conditions of approaching storms. This multi-model approach also would measure the impacts of hurricane after they pass.
“If you are just looking at only one model you’re prone to make several significant errors in your assessments,” he said.
This research contributes to two programs sponsored by the National Oceanic and Atmospheric Administration (NOAA) that aim to improve hurricane tracking, forecasting and understanding of potential impacts. The URI group is also offering its expertise to the state Beach SAMP project to help improve hurricane risk analysis in Rhode Island.
Grover Fugate, director of the state Coastal Resources Management Council (CRMC), the agency overseeing the Beach SAMP, said having this information helps cities and town better understand the risks and prepare.
“We really need to start thinking about these practices and how we put those in proactively, so that we can act when the storm comes,” Fugate said.
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