Ida Slams Louisiana – First Look

August 29, 2021

Bob Henson and Jeff Masters for Yale Climate Connections:

Category 4 Hurricane Ida struck a catastrophic blow on Louisiana, making landfall at the key oil industry hub of Port Fourchon at 11:55 a.m. CDT August 29, with 150 mph winds and a central pressure of 930 mb. Remarkably, today is also the 16thanniversary of Hurricane Katrina’s devastating landfall in Louisiana and Mississippi in 2005. Katrina, the most expensive weather disaster in world history, at $176 billion, caused between 1085 and 1389 deaths.

Only four hurricanes (all Cat 5s) have made landfall in the contiguous U.S. with stronger winds than Ida, and Ida is tied with Laura of 2020 and the 1856 Last Island Hurricane as the strongest ever to hit Louisiana. As measured by central pressure at landfall, Ida ranks as the ninth-strongest to hit the contiguous U.S., and second-strongest to hit Louisiana. Only Hurricane Katrina of 2005, with a 920 mb pressure at landfall near Buras, had a lower pressure.

Ida is the second major hurricane of the 2021 season; Grace also became a major hurricane earlier this month as it hit Mexico. The most recent Atlantic hurricane season with two or more major hurricanes by August 29 was 2005 – the year of Katrina.

Ida put on a furious display of rapid intensification overnight, with the pressure dropping from 985mb to 929mb (a fall of 56 mb) in 24 hours. As documented by Sam Lillo (see Tweet below), only nine hurricanes on record in the Atlantic have done this, with Ida being the furthest north, and the one closest to a U.S. landfall. In one 12-hour period, Ida’s pressure fell by a remarkable 40 mb – the third fastest pressure fall observed in a Gulf of Mexico hurricane since 1979. Sea surface temperature of 30-31 degrees Celsius (86-88°F) and the warm Loop Current eddy that Ida passed over were both key factors in its intensification.

At landfall, Ida was undergoing an eyewall replacement cycle (ERC), which halted intensification just before landfall, causing the pressure to rise from 929 mb to 930 mb. The ERC kept the winds at the core from increasing further, but greatly broadened the area experiencing hurricane-force winds. This is overall a bad thing for Louisiana, as it will result in more wind damage.

According to Brian McNoldy, Ida’s Integrated Kinetic Energy (IKE, a measure of the total destructive power of hurricane, based on the size of its wind field) was 36 terajoules (TJ) at 11 a.m. EDT Sunday, an increase of 64% from the 22 TJ it had 24 hours previously. For comparison, Hurricane Katrina’s IKE at landfall was 113 TJ. Thus, Katrina’s surge had a lot more destructive power than Ida’s. However, Ida’s wind damage and fresh water flooding damage will likely exceed that of Katrina – particularly since Ida is hitting a key area of U.S infrastructure.

2 Responses to “Ida Slams Louisiana – First Look”

  1. redskylite Says:

    As the 2021 hurricane season starts to peak, will it be as severe as 2020 ?

    “2020 had 102 tropical storms, well above world average, NOAA report says

    In both the Northern and Southern Hemisphere, scientists recorded 102 tropical storms. It’s a total far above the 1981–2010 average of 85, according to the study.”

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