As Tropical Storm Bertha gains strength crossing Louisiana and heading towards Texas, everyone is talking not so much about the wind speeds, but the flooding rain and storm surge that threatens life and property.
What is Storm Surge?
Put simply, storm surge is the level at which sea water rises above its normal level. Much like the way a storm’s sustained winds do not include the potential for even stronger gusts, storm surge doesn’t include the wave height above the mean water level. Surge is also the amount above what the normal tide is at a time, so a 15-foot storm surge at high tide can be far more devastating than the same surge at low tide.
As ABC News reports, the most common way to measure a hurricane’s strength is the Saffir-Simpson Wind Speed Scale that assigns a category from 1 to 5 based on a storm’s sustained wind speed at its center, with 5 being the strongest. But that only tells part of the story.
What makes Storm Surge so Dangerous?
While wind can tear off roofs, knock down trees and snap power lines, storm surge can push buildings completely off their foundations, can trap and even drown people in their homes, wash out roads and bridges, toss boats inland and hammer anything in its path. “The leading cause of death from hurricanes is water, not wind,” said Craig Fugate, the former director of the Federal Emergency Management Agency (FEMA) who previously ran Florida’s emergency management.
For example, in the case of 2024’s Hurricane Helene, predicted storm surge was devastating in the coastal areas of the state’s Big Bend, where the peninsula meets the Panhandle. The surge from Helene was said to be between 15 and 20 feet (4.5 to 6 meters). That’s a tidal wave that measures higher than a single story house.
A Homebrew Tropical Storm
Bertha is what AccuWeather meteorologists refer to as a homebrew tropical storm because it formed within a few hundred miles of the United States coast—in this case, over the northeastern Gulf. This particular area was under meteorologists’ watchful eye for well over a week before the storm formed.
“Tropical Storm Bertha has made landfall in far eastern portions of St. Bernard Parish, Louisiana, as of mid-afternoon,” AccuWeather Lead Hurricane Expert Alex DaSilva said. Bertha has maximum sustained winds of 45 mph with a low-level circulation separated from the vast majority of thunderstorms to the south.
How Does Bertha’s Storm Surge Compare to Hurricanes?
Hurricane Katrina is largely remembered for causing flooding in New Orleans. That wasn’t from storm surge, but rather the failure of levees protecting the city. But further east, Mississippi was devastated by up to 28 feet (8.5 meters) of surge.
Afterward, parts of the Mississippi coast looked as if someone took heavy equipment and cleared out everything within 300 yards (274 meters) of the shore, Fugate said. “It took the gambling casino boats and put them on the other side of the road. The Waffle Houses were nothing but slabs,” Fugate said.
Even though Bertha is far from some of these powerhouse hurricanes that have struck the central Gulf Coast over the years, its impacts from heavy rain and rising Gulf waters should not be taken lightly.
Much of the thunderstorm activity with Bertha has been south of the center and over the Gulf. However, as the storm moves inland, some changes in the structure of the storm’s showers and thunderstorms are likely, with bands of heavy rain forecast to wrap over the Florida Panhandle, Alabama and Mississippi, and especially over southern Louisiana, DaSilva stated.
There is the potential for a few severe thunderstorms to occur along Bertha’s westward path. With these, a couple of tornadoes and waterspouts could be spawned. “Even though Bertha will bring its share of problems from flooding downpours, storm surge and gusty winds, people along the central Gulf Coast should feel fortunate in that wind shear likely prevented the storm from becoming a major hurricane,” DaSilva said.
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