by Duluth guest » April 2, 2024, 2:58 pm
Scott wrote: ↑April 1, 2024, 1:08 pm
How outdated are the depth charts that the captain or mate did not know how deep it was?
The water levels at harbors on the extreme ends of a large lake fluctuate with variations in atmospheric pressure, wind speed and direction, etc. A few inches of change at just the right or wrong time can make a big difference. Burns Harbor was being loaded during one of the biggest water level swings of the year so far at Duluth-Superior. A sustained long period of easterly winds pushed a lot of water into the western end of Lake Superior, raising water levels significantly above the month's average, then those winds slacked and blew from the west instead, causing a big drop in lake levels.
One can set the date range on the water level plotting tool for the Duluth Harbor water level gauge, linked here:
https://tidesandcurrents.noaa.gov/water ... id=9099064
The plot date range can be set for up to 30 days or so. To get an idea of what Burns Harbor was contending with, set the date range from sometime in early March up through around March 30th, when Burns Harbor lightered to H Lee White and finally got clear. Note that Burns Harbor was likely loading at BNSF from around 10am on March 24th through sometime in the evening of March 25th or into March 26th, but then the ship stayed put at the dock waiting out winds and waves on the open lake until trying to leave late on the 26th or on the morning of the 27th only to find themselves loaded onto the bottom.
[quote=Scott post_id=262966 time=1711994884]
How outdated are the depth charts that the captain or mate did not know how deep it was?
[/quote]
The water levels at harbors on the extreme ends of a large lake fluctuate with variations in atmospheric pressure, wind speed and direction, etc. A few inches of change at just the right or wrong time can make a big difference. Burns Harbor was being loaded during one of the biggest water level swings of the year so far at Duluth-Superior. A sustained long period of easterly winds pushed a lot of water into the western end of Lake Superior, raising water levels significantly above the month's average, then those winds slacked and blew from the west instead, causing a big drop in lake levels.
One can set the date range on the water level plotting tool for the Duluth Harbor water level gauge, linked here: [url]https://tidesandcurrents.noaa.gov/waterlevels.html?id=9099064[/url]
The plot date range can be set for up to 30 days or so. To get an idea of what Burns Harbor was contending with, set the date range from sometime in early March up through around March 30th, when Burns Harbor lightered to H Lee White and finally got clear. Note that Burns Harbor was likely loading at BNSF from around 10am on March 24th through sometime in the evening of March 25th or into March 26th, but then the ship stayed put at the dock waiting out winds and waves on the open lake until trying to leave late on the 26th or on the morning of the 27th only to find themselves loaded onto the bottom.