Response of the Mississippi Bight and Sound to the Passage of Tropical Storm Cindy Through the Northern Gulf of Mexico

Damage inflicted by tropical storms and hurricanes on coastal communities and industries has become a growing concern in recent decades. Consequently, utilizing products from existing ocean observing platforms, ocean modeling forecasts and satellite data helps to identify the effects of individual storms on the northern Gulf of Mexico. Using data from the jointly-operated United States Geological Survey and Mississippi Department of Marine Resources (USGS-MDMR) hydrological stations, National Oceanic and Atmospheric Administration (NOAA) tide gages, and the Central Gulf of Mexico Ocean Observing System (CenGOOS) high frequency radar (HFR) network, we tracked temperature, salinity, water level and surface current changes in the Mississippi Sound and Bight during June 2017. We performed time series analyses and compared conditions during the buildup and passage of tropical storm Cindy to climatological values as well as to satellite observations and results from a regional application of the Navy Coastal Ocean Model (NCOM). Elevated salinities proceeded Cindy's landfall on June 22, 2017, while anomalously fresh water marked all Mississippi Sound stations afterwards. Onshore surface currents dominated the Mississippi Bight, and current speeds exceeded more than four times the climatological average in the southeastern Bight. Indeed, regions of enhanced current speeds were observed throughout the month of June 2017. Tidal ranges in the Mississippi Sound were on average half a meter higher than predicted, and Shell Beach (Louisiana) and the Bay Waveland Yacht Club (Mississippi) saw extended periods where tides exceeded one meter above predicted values. These results help to quantify the tidal inundation caused by Cindy but also illustrate the massive riverine discharge driven by the storm's precipitation. Model results provide information on areas of the study region not covered by measurements; additionally, comparing observations to model products helps estimate model effectiveness for storm events. Though Cindy never became a hurricane, the storm caused extensive and widespread coastal flooding, strong surface currents and salinity fluctuations in the northern Gulf of Mexico.