Wind, Storm Surge Among Ida's Many Threats

Dangerous Category 4 Major Hurricane Ida is churning over northern the Gulf of Mexico, and its sights are clearly set on the central Gulf Coast for a landfall later today. Hurricane Warnings are in place for much of the Louisiana coast, with Storm Surge Warnings stretching from western Louisiana to Mississippi. What threats can be expected as Ida nears the coast?

• Winds

One of the most damaging aspects of a hurricane is its winds. As Ida makes landfall, Ida will be at “major” status, with sustained winds of 140-155 mph. The strongest winds are typically found near where the storm comes ashore and to the north and east of the center. In this case, this will likely be found in a ribbon stretching from Vermillion Bay to Baton Rouge to the New Orleans metro. Depending on the exact point of landfall, cities in this area, including Lafayette, Morgan City and the western suburbs New Orleans could see sustained winds of 70-100 mph, with gusts as high as 100-130 mph this afternoon and evening. The storm will weaken somewhat as it moves inland, but sustained winds of 50-75 mph and gusts of up to 100 mph are possible into Baton Rouge, eastern Louisiana and southwestern Mississippi on Monday.

• Rainfall

Tropical downpours can be expected as Ida makes its approach to the central Gulf Coast this weekend. Unfortunately, the ground has already been primed for significant flooding by an unrelated weather system that brought as much as an inch of rain to southeastern Louisiana on Friday. After relatively dry weather Saturday, Ida-related rainfall will develop this morning across southern Louisiana and southern Mississippi.

The rain will increase in intensity along and south of the Interstate 10 and 12 corridors in Louisiana this evening as it spreads northward into the Mississippi Valley. The heaviest downpours will come late today into Monday, where as much as 7 to 10 inches of rain will fall across the region on that day alone. By the time the rain finally winds down later Tuesday, totals from Ida will very likely be in the 10 to 15 inch range for New Orleans and Baton Rouge, with locally as much as 17 to 20 inches.

Drenching rainfall will follow Ida’s path into the Lower Mississippi Valley, with locales such as Jackson, Miss., and Memphis and Nashville, Tenn., poised to see 3 to 6 inches of rain through the middle of the work week. It goes without saying that this much rain will cause flooding, particularly in areas that have seen heavy rain in recent days and weeks.

• Storm Surge

As residents of Louisiana know all too well, storm surge is one of a hurricane’s strongest weapons. Particularly to the east of the center, the strong winds push the seawater toward the coast, causing it to pile up above what the normal tide level would be. The constant push of water and waves can produce prolific damage to coastal structures and push the water onto the low-lying ground.

2005’s Hurricane Katrina brought storm surges in excess of 10 feet, which ultimately overtopped the levees, flooding New Orleans. Ida’s storm surge won’t be quite this high in New Orleans, with waves of 4 to 8 feet above normal levels into Lake Pontchartrain and along the Mississippi and far-eastern Louisiana coast.

The highest surges will be right around where the storm moves ashore, potentially as high as 10 to 15 feet between Morgan City, La., and the mouth of the Mississippi River. Even as far west as southwestern Louisiana and as far east as the Alabama coast, a storm surge of 2 to 4 feet can be expected. These surges will produce high surf during the high tide cycles through this morning.

• Severe Weather

Thanks to an extreme amount of spin associated with the storm, hurricanes often produce tornadoes. While the twisters are often short-lived, they can cause significant damage in the brief path and time that they are on the ground. Beyond the tornado threat, Ida is very likely to bring frequent lightning in its thunderstorms, particularly near the center of the storm.