Thursday, November 15, 2018

Michael’s Damage and the Future of Hurricanes in the Atlantic

This past October, the Florida panhandle was hit with hurricane Michael. Storm surge, coastal erosion and inland flooding are among the most dangerous natural hazards unleashed by hurricanes. The USGS, the National Hurricane Center and other agencies closely monitor hurricanes. The USGS has computer models for forecasting the storm’s impact, and sophisticated equipment for monitoring actual flood and tide conditions. In addition, the USGS compares the National Oceanic and Atmospheric Administration coastal photos taken in 2017  to NOAA photos collected the day after Hurricane Michael made landfall in order to document the hurricane’s impact on the coast, and to fine-tune coastal change forecasting models.
Mexico Beach before Michael from USGS

Mexico Beach after Michael from USGS

When a storm is about to strike the U.S. Atlantic or Gulf coast, the team forecasts the likelihood of coastal erosion and other changes, using a computer model that incorporates the National Hurricane Center’s storm surge predictions and National Oceanic and Atmospheric Administration wave forecasts. The USGS model adds information about the beach slope and dune height to predict how high waves and surge will move up the beach. The model forecasts three types of storm impact to the dunes that protect coastal communities: erosion, overwash, and inundation, or flooding that reaches over and behind the dunes.

According to Kara Doran, the USGS Coastal Change Hazards team leader the low-altitude oblique photos give a clearer view of the beach and dunes. The USGS can see whether the storm surge and waves altered or eliminated that protective barrier, and what happened to the houses and roads behind the dunes. Though the destruction as seen above is shocking according to Doran the USGS’s preliminary analysis indicates that the forecasting models performed fairly well at predicating what areas would be affected by storm surge overtopped the dunes.

One area that saw significant coastal change that was not predicted by model was on T.H. Stone Memorial St. Joseph Peninsula State Park. As seen in the photos below, Michael’s rough waves and surge carved a new breach into the peninsula, washing out the road and turning part of the park into an island as seen below in the USGS photos.

It is not known if this kind of damage is the future of the coastal areas as the climate warms. According to NOAA, observed records of Atlantic hurricane activity show some correlation, on multi-year time-scales, between local tropical Atlantic sea surface temperatures and the power of the storms. "If this statistical relationship between Atlantic sea surface temperatures and hurricane activity is used to infer future changes in Atlantic hurricane activity, the implications are that the forecasted large increases in tropical Atlantic sea surface temperatures projected for the late 21st century would imply very substantial increases in hurricane destructive potential–roughly a 300% increase by 2100."

On the other hand, Swanson (2008) and others noted that Atlantic hurricane power dissipation is also well-correlated with other Atlantic sea surface temperature indices besides tropical Atlantic sea surface temperature alone. "This a crucial distinction, because the alternative statistical relationship between the hurricane destructive potential and the relative sea surface temperature measure implies only modest future long-term trends of Atlantic hurricane activity with climate warming. So, we don't really know."

From Department of the Interior, U.S. Geological Survey press release.

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