Saffir-Simpson Scale splits wind, storm surge relationship

Myrtle Beach, SC - By Katy Morgan - bio | email

MYRTLE BEACH, SC (WMBF) - Wind speed and storm surge have sat side-by-side on the Saffir-Simpson scale since it's development in the 70s, but now, that's changing.

National Hurricane Center Director Bill Reed explained meteorologists never liked the relationship to begin with.

"If I took Hurricane Ike that produced 15 to 20 ft storm surge off Texas and Louisiana, and ran it against North Miami to Palm Beach, FL, I'd only get 7 feet. Same storm," he said.

In other words, the storm surge forecast relies heavily on the local geography. A uniform scale is not an accurate way to come up with that forecast.

"The bathymetry", Reed explained, "or the sea shore of the ocean as it comes up to your beach plays a role in it. The size of the hurricane plays a role in it. The direction plays a role, where as the max wind is 100 mph no matter how it comes at you. That's why we separated the two."

So how does the bathymetry compare along the Carolina coastline?

The Grand Strand sits on a generally soft-slopping shelf. The gradual climb from the ocean floor to the shore line, combined with the right storm ingredients, could mean an increased storm surge compared to other beaches around the United States.

For 10 years, Horry County Geographical Information System has been using this technology to map communities that could potentially be affected by storm surge along the Grand Strand.

"We do this to give people an idea of what could happen," Justin Schools, an Horry County GIS employee, said. "It's not an exact science of, 'This is what is going to happen if a Category 5 came and your house is underwater.' It doesn't mean that is going to be the case. It's just a good estimate. It's what we can use to the best of our knowledge."

Using contour lines, or lines of constant elevation, Schools can determine which areas along the Horry County coastline would be most vulnerable to storm surge. From his research, Schools said the south end of Horry County would most likely see the worst storm surge, with the appropriate placement of a land falling hurricane.

Schools, however, reminded people who live along the coastline not to take the maps as a sure thing.

"What people can take away from this is this is a possibility. It's the worst case scenario. It's not the [total] worst case scenario," he said.

It's just another way to stay prepared during the hurricane season.  If you would like to learn more on storm surge potential in your neighborhood, you can call Horry County GIS at 915-5245

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