Hurricane Laura: The danger of storm surge, explained

Eric Thayer/Getty Images

Why this storm could bring life-threatening flooding.

Hurricane Laura made landfall at 1 am ET Thursday in Cameron, Louisiana, as a fierce Category 4 hurricane with 140 mph winds. It has since downgraded to a Category 2 hurricane, with wind speeds of 100 mph, and is moving north.

But perhaps the most dangerous part of the storm may be the storm surge that still threatens coastal areas.

Storm surge, or coastal flooding, tends to be the deadliest aspect of hurricanes. It results from the storm’s winds pushing water onshore several feet above the normal tide, and it can trap people in their homes, wash away houses, and make rescue missions harrowing and slow. Rising sea levels linked to climate change have also increased the risk of storm surge and property damage in coastal cities and regions.

The National Hurricane Center (NHC) said Thursday morning a storm surge warning was still in effect from High Island, Texas, to the mouth of the Mississippi River; this kind of warning means a danger of life-threatening flooding. People located in these zones should follow evacuation and other instructions from local officials.

The surge could be higher than 10 feet, and even up to 20 feet, along some areas of the Louisiana coast if the peak hits at high tide:

NOAA/National Weather Service

But so far, the highest storm surge reported seems is 9 feet, according to meteorologist Chris Gloninger:

But other meteorologists say it’s too soon to assess the total storm surge from Hurricane Laura. The water pushed on land by the winds could also still reach up to 40 miles inland “and flood waters will not fully recede for several days after the storm,” according to the NHC.

The larger the area with tropical storm-force winds, the more potential for those winds to push water onshore, and the greater the impact of storm surge, Colorado State University atmospheric scientist Chris Slocum says. Portions of Louisiana, Mississippi, and Arkansas could also see up to 6 to 12 inches of rain with isolated totals of 18 inches from Laura, which will add to the floodwaters.

Sam Ellis/Vox

The storm surge “is a life-threatening situation,” the NHC warns in its latest forecast. “Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other dangerous conditions.”

How to follow Hurricane Laura:

• The National Hurricane Center has a page updating every few hours with the latest watches and warnings for Laura. Check it out.
• Follow the National Hurricane Center on Twitter; it will provide updates with all the latest forecasts, hazards, and warnings.
• Follow the Capital Weather Gang’s Twitter account. These folks tend to live-tweet storm updates.
• Here’s a Twitter list of weather experts via meteorologist and journalist Eric Holthaus. These experts will give you up-to-the-second forecasts and warnings.

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