Storm Surge

BATON ROUGE, LA (WAFB) - Rising water is often the biggest threat from tropical systems in south Louisiana, so there are new efforts to highlight that danger.

With US coastal populations continuing to increase, the potential losses to both life and property from storm surge are soaring. The National Hurricane Center hopes to emphasize that threat with new products this year.

The University of Miami recently opened a research facility it claims is the only one in the world capable of simulating the winds and waves of a Category 5 hurricane.

SUSTAIN, which is short for Surge Structure Atmosphere Interaction, uses a tank holding 38,000 gallons of seawater to simulate interactions between the atmosphere and ocean. It will also be used to study the impacts of waves and storm surge on coastal structures.

On August 28, 2012, a storm named Isaac briefly developed into a minimal hurricane while meandering along the Louisiana coast. Most people in south Louisiana didn't seem too worried about Isaac, calling it only a Category 1, but forecasters tried to sound an alarm about the incoming storm surge.

"Seven to 11 feet on the eastern facing shores of Plaquemines and St. Bernard parishes," Meteorologist Steve Caparotta said. "About three to maybe as much as eight feet in Lake Pontchartrain."

In spite of those warnings, many were shocked by the extent of the flooding.

"I parked here during Katrina," one man said. "I brought relief supplies. I have never seen nothing like this, not even with Katrina."

"All of the old people say that their grandfathers never saw anything like this, never told them of anything like this before," said Bill Roux with the Ascension Parish Drainage Board.

Storms like Isaac make it clear that the Saffir-Simpson Scale, which is designed to rank hurricane winds on a scale from one to five, fails to convey the full potential of a storm's impacts, especially storm surge.

"The category does not really portray the impacts," said Ken Graham with the National Weather Service in New Orleans. "Category 1 Hurricane Isaac had the impacts of a much larger hurricane because it's about the size. It's about the speed of the storm. I mean, think about it, 12 to 13 feet of storm surge and 8.5 in Lake Pontchartrain, with all of the wind as well and the rain. Just a category doesn't do the job in portraying all those impacts."

Beginning this year, the National Hurricane Center will begin issuing experimental storm surge watches and warnings. The goal is to highlight the potential for the threat of rising water, even where winds from a tropical storm or hurricane may not be a huge issue.

"You may not be under a hurricane warning, but storm surge is such a huge threat for us here in Louisiana that we'll have a warning up for the storm surge," Graham added.

Another fairly new tool available to forecasters and emergency managers this year is a potential storm surge flooding map. The maps will typically be released for coastal areas once a tropical storm or hurricane watch is posted. The goal is to give people an idea of just how high the storm surge may get.

"The game-changer about it [is] for the first time, it will actually be inundation. So, it's actually the water, basically, up your pant leg. So, it's actually water on the ground. That's new," Graham explained.

When looking at the inundation maps, you can interpret the numbers at a given place to mean there's a 90 percent chance that the surge will be that value or lower. Another way to look at it is to consider those inundation numbers as a reasonable worst case scenario for that particular storm.

One thing to keep in mind is that as the forecast track for a given storm changes from advisory to advisory, the values on those new inundation maps are also likely to change.

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