NOAA’s High Tide Bulletin and the Prediction of High Tide Flooding

High tide or “nuisance” flooding is tidally driven coastal inundation. Decades ago, coastal flooding in the United States was almost exclusively driven by large storms, however in many locations flooding now frequently occurs at high tide with little or no contribution from weather. The National Oceanographic and Atmospheric Administration (NOAA) estimates that relative sea level rise since the 1960s has increased high tide flooding by as much as 300-1000 percent depending on the location along the U.S. coast. Sea level rise over the coming years and decades will increase the number and severity of flooding events that occur from tides alone.

Here we present the High Tide Bulletin, a new NOAA product that provides seasonal outlooks of when and where high tide flooding may occur. The Bulletin is based on tide predictions generated from water level observations collected at NOAA tide gauges throughout the coastal U.S., and highlights key regional distinctions in seasonal high tides. We also explore potential enhancements to enable the seasonal to annual prediction of daily high tide flooding likelihood. National Weather Service-derived minor flood thresholds at NOAA tide gauges are coupled with sea level trends and historic distributions of non-tidal residuals to estimate a location’s daily flood likelihood. Where flood frequencies tend to be dictated by changes in the tide itself, more skillful predictions are found. Skill decreases for regions where flooding is less tidally- and more weather-driven, such as locations in the Gulf of Mexico with small range of tide. Further exploration of potential forecast approaches will be made through collaborative efforts with federal and academic partners to predict seasonal non-tidal water levels using an ensemble of dynamical and statistical models.