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Impact Differences When a Hurricane Parallels the Coast Instead of Making Landfall

At a Glance

A direct landfall can have more serious impacts.
When hurricanes track parallel to the coast, impacts can be more widespread.

When considering potential impacts from a hurricane, the angle of approach to the coast is one important factor.

Among other factors such as the storm's intensity, forward speed, size, and shape of the coast, how the tropical cyclone tracks near a coast can make a big difference in terms of the severity of storm surge, coastal flooding, heavy rain and damaging winds. It will also determine how far-reaching these impacts will be.

Here are the key differences a different angle of approach can make:

1) Direct Landfall

When a hurricane makes landfall it means that the center of the circulation crosses over land, which leads to different consequences than if the system only approaches the coast.

A direct landfall will lead to the potential for greater storm surge in that location, particularly to the immediate right of the storm's path. Storm surge is typically the deadliest threat from a hurricane.

Storm surge, according to the National Hurricane Center, is "an abnormal rise of water generated by a storm, over and above the predicted astronomical tides. The rise in water can cause extreme flooding in coastal areas particularly when storm surge coincides with normal high tide." Storm surge is created when strong winds from the storm push water toward the shore.

(MORE: More Than 75 Percent of U.S. Tropical Cyclone Deaths Are From Water)

In this case, the hurricane's most intense winds, found in the eyewall, hammer at least a part of the coast, and to some extent inland.

2) Track Parallel to the Coast

When a hurricane, instead, tracks parallel to the coastline the severity of impacts usually lessens, the area that experiences the effects of the storm increases, as well as the difficulty of the forecast.

The storm surge produced at a given location likely will be reduced. However, the closer the center of the tropical cyclone comes to the coast, the worse the conditions.

However, as the storm continues to track parallel to the coast without making landfall, hurricane conditions, including strong winds and heavy rains, may impact many more coastal residents.

(MORE: Explaining the Cone of Uncertainty)

Furthermore, small deviations in the forecast track of a "paralleling, but offshore" hurricane can change coastal impacts dramatically.

A mere 5-10 miles difference in the track could mean the difference between a swipe of damaging winds from the eyewall, or borderline tropical storm-force winds. Or it could mean the difference between, say, over a foot of rain or just an inch or two.

Just because a hurricane does not make landfall does not mean it isn't dangerous.