Downburst Winds Caused CMA CGM Containership to Breakaway in New Orleans: Report

A sudden downburst generating severe, unforecasted winds caused a CMA CGM containership to breakaway from a pier and damage equipment at the Napoleon Avenue Container Terminal in New Orleans last summer, the National Transportation Safety Board said Thursday.  

Marine Accident Brief 21/18, issued today, details the NTSB’s investigation into August 2, 2020 accident, when a localized thunderstorm popped up and passed through the area as longshoremen loaded and unloaded cargo from the 1,099-foot-long CMA CGM Bianca, a 8,533 TEU capacity ship.

Ten of the vessel’s 16 mooring lines parted in the high winds, and the ship moved away from the pier. Containers lifted by shoreside gantry cranes struck the ship. One damaged container dropped in the water spilling a cargo of plastic pellets, known as nurdles. A crane operator suffered a minor injury and damages totaled approximately $15.1 million.

In its report, NTSB said the crane operators and CMA CGM Bianca’s crew reported extreme high winds that came on “in seconds” during heavy rains.

Rains were heavy enough to completely obscure the visibility of security cameras at the terminal. Although the closest official weather station recorded winds peaking at 31 mph, a vessel located very close to the accident reported a wind gust at 73 mph. The CMA CGM Bianca’s master said that the storm was, “in the form of a tornado.” According to the NTSB report, evidence suggests that the CMA CGM Bianca was struck by outflow winds from a downburst.

The National Weather Service classifies downbursts as “powerful winds that descend from a thunderstorm and spread out quickly once they hit the ground. These winds can easily cause damage similar to that of a EF0 (65–85?mph winds) or even EF1 (86–110?mph winds) tornado and are sometimes misinterpreted as tornadoes.”

NTSB investigators determined the probable cause of the accident to be the sudden onset of unforecasted severe winds likely originating from the outflow of a thunderstorm generated downburst. 

Marine Accident Brief 21/18 is available on the NTSB’s website at https://go.usa.gov/xMBKr.

Updated: October 26, 2023 (Originally published September 16, 2021)

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