Heavy rain and strong winds are not the only reasons for concern when a tropical system like Isaac moves ashore.
Storm surge is the sudden rise of the ocean that moves inland as the eye of the hurricane makes landfall. Most of the storm surge occurs on the right side of the track. This is where the winds push the ocean surface ahead of the storm.
As the hurricane approaches land, its wind drives water toward the shore. Wave after wave hits the coast as tons of moving water slams into any structure on the coastline.
Low pressure in the hurricane sucks the water to the middle like a straw raising the ocean level but the strong winds around the eye are responsible for storm surge.
The winds act like a plow causing the water to pile up. Over deep water the rise in sea level is small. But as the hurricane approaches land the water begins to build up and when hurricane makes landfall the water spills into low-lying areas causing major coastal flooding.
The intensity of storm surge depends on the wind strength, topography, tides and speed of storm motion. A stronger hurricane combined with high tide will produce the strongest storm surge.
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