According to the National Hurricane Center, “a storm surge watch is defined as the possibility of life-threatening inundation from rising water moving inland from the shoreline somewhere within the specified area, generally within 48 hours, in association with a tropical, subtropical, or post-tropical cyclone.” A storm-surge warning means a storm surge is imminent within 36 hours.

Storm surge is not to be taken lightly. It is considered a tropical storm’s silent killer. According to survey results published in 2015, “many coastal residents lack sufficient knowledge about their vulnerability and do not comprehend the nature of storm surge.”

This is obviously a major problem for weather communicators, and that was shown in 2005 when nearly 180 people died in Mississippi from Hurricane Katrina’s storm surge. “A post-Katrina behavioral survey revealed that most of the respondents in Alabama, Mississippi, and Louisiana could not interpret an NWS storm surge forecast correctly,” the authors of the survey concluded.

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With storm-surge warnings, more lives could be saved. It’s a more advanced, but simpler to interpret, early-warning system that uses standard terminology in regards to other weather hazards such as tornadoes and flash floods.

Storm surge is generated by strong winds that push surface water toward the shoreline. But “storm surge is a very complex phenomenon because it is sensitive to the slightest changes in storm intensity, forward speed, size (radius of maximum wind), angle of approach to the coast, central pressure and the shape and characteristics of coastal features such as bays and estuaries,” the National Hurricane Center says.

The destructive power of a storm surge is also dependent on the bathymetry of the ocean, or the topography of the ocean floor. Coastlines that are close to the continental shelf and are rather steep will experience smaller storm surges than ones that are shallow and rise gradually.

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The bathymetry of the Big Bend of Florida, where this week’s tropical storm is expected to make landfall, is rather shallow, so even a minor cyclone can create a rather big storm surge.