Roll clouds on Great Lakes

[JosephT]

So I'm sailing down Lake Michigan several miles off the Wisconsin coast. A thunderstorm passed from west to east, then a few hours later this strange roll cloud comes creeping off the shore very similar to the one in this video. I was at the helm so I didn't have time to pull out my video camera. I've never seen these while offshore sailing on the ocean. They appear to occur quite a bit on the Great Lakes. They are VERY long and look like an avalanche rolling down a snow mountain.

I would be interested to learn more about strange clouds and weather phenomenon from anyone who has stories and pics/videos to share.

 

[Doug Lord]

Roll Clouds

Thanks, Joseph! I've never seen that before-fascinating and kinda weird...

 

[JosephT]

Yeah I was skippering a boat from Mackinac Island to Chicago. We hit a few storms along the way. A point to make is when you approach a roll cloud like this DO EXPECT a sudden shift in wind direction.

On the east side of the roll cloud the wind was blowing from the east. On the west (after I crossed under the big fast white cigar of a cloud!) the wind was shooting up fast from the south.

I had never seen one before so I decided to steer east just to see how the sails would react. Fortunately I could see the wind along the waves cutting parallel with the roll cloud and I instantly went into a downwind situation. Weeee!!!!

After a while the roll cloud dissipated, but the southern winds remained.

Hats off to Mother Nature for putting on a good show.

 

[philSweet]

I've seen them twice. As a kid in Memphis, immediately followed by severe gusts and biggish hail and a great big conventional thunderhead. And in Key Largo, accompanied by freakish winds topping 85 knots for 15 minutes, with NOAA broadcasting 10-15 mph and their stock chamber-of-commerce weekend forecast. In Memphis, there were two of them back to back. They were bigger than the one in the video, but low like that. In Florida, there was a whole chain of them, and they were much higher up and much bigger. Floor was maybe 3000 feet and the clouds were over 100 miles long, based on reports from Key West to Key Largo, and the fact you could see them coming for about 20 miles. The windstorm in Florida was a blue squall - not a cloud in the sky except for the jellyroll clouds. There is a fair amount of video of these thing out there. See Arctus cloud.

Edit. Cross posted with JosephT. The videos don't do these things justice at all. They are absolutely amazing to see.

 

[JosephT]

Holy cow...85kt winds. That's a pretty sudden shift. I would say the winds I encountered were about 45 knots for a good 15min. Unless you steer away from the cloud that wind shift will stay with you for as long as that big cigar of a cloud is cruising over your head.

Earlier on we were blasted by a severe thunderstorm that blew east out of Wisconsin, complete with tornado warnings and all the bells & whistles. A few hours after it passed over this roll cloud (one of 3) came rolling off the coast of Wisconsin.

I love sailing in storms and truly appreciated the experience.

 

[philSweet]

The 85 knots figure came from a big yacht that was transiting Hawk Channel and managed to get his hooks down when CH 16 went wild with gust reports. He said his masthead gauge went to the 85 knot pin on the first gust and never moved for 15 minutes. Peak gusts were 100 plus.

 

[JosephT]

You've definitely got to drop the sails quick in a situation like that. If not, you risk shredding some expensive sails and who knows what else.

 

[hoytedow]

https://en.wikipedia.org/wiki/Morning_Glory_cloud
In Australia they call them morning glory clouds.

 

[JosephT]

Thanks for the details hoytedow. It appears they are not well understood. Best to avoid them or risk sucked into into the time space continuum.

 

[hoytedow]

Who knew that the space time continuum is best represented by a pitted olive, or Perpetuum Jazzile?

https://www.youtube.com/watch?v=xbMuLAQMx9c