Chi-Mac Autopsy: Anatomy Of A Deadly Storm

26 Jan

In 2011, the storied Chicago-Mackinac Race experienced its first weather-related fatalities when 2 sailors died after their sailboat, Wiingnuts, was capsized by a powerrful thunderstorm

For the weather-geeks among you, the website LakeErieWx has released a highly detailed analysis of the explosive thunderstorm cells which swept the fleet. 

It's an interesting report which emphasizes the fact that any offshore racing boat needs to be ready for pretty

much ANYTHING.

The conclusion (full report is here):

The data from the base reflectivity and base velocity radar imagery suggests that the waters west of Charlevoix, MI were buffeted by a combination of strong winds from the bowing segment to the west-northwest and a strong downdraft from a supercell thunderstorm to the north. Wind speeds of 45 to perhaps 70 knots are supported by radar data and observations. Although the weather station at Charlevoix observed 64 knots, it is possible that friction over land diminished the wind speeds associated with the land-falling storm and that this peak observation was somewhat less than what would have been encountered by the racers offshore.

In addition to very strong winds, many of Chicago-Mac racers reported wave heights as high as 6 to 8 feet, a significant difference from the observations at Buoy 45002. Of course, the observations at Buoy 45002 represent the conditions at only one specific point and the racers were spread out over a large area. For those competitors who were much closer to the Michigan shore, it is possible that the additional fetch supported the development of much larger waves. It is also possible that the combination of the winds from the bowing segment and the supercell downdraft combined in the area to produce significantly larger waves.

Veteran Chicago-Mac racers have encountered similar conditions during previous races and understand that coping with severe weather is part of the challenge. Skippers must prepare their boats, train their crew, maintain a watchful eye for approaching storms and "the dearest friend (and most menacing foe) of all sailors — the wind."

 

 

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