September 4, 2010

Chubasco—the anatomy of a storm

This is what a storm looks like when it's breaking down. When it's pumping you don't turn on the computer and take a screen shot...

Last night we got the weather we’ve been hoping to avoid. When we pulled down the satellite images of the Sea of Cortez there were massive areas of convection on the mainland side, which were moving our way. After making our own forecast of, ‘we’re going to get smacked’ we checked Stan’s Chubasco forecast by SSB: 

“Tonight on the Mainland there is almost continuous convection on the beach from Mazatlan north to Kino. All of this convection is expanding and moving to the west. I don't think the convection will survive the trip across the Sea, but it might. So I would say there is a chance of a Chubasco all along the Baja peninsula. If it were me, I would go to bed early and get up at 1am local time and see what it looks like.”

Stan seemed a bit more optimistic than we felt, but we prepared the boat for a blow and I headed to bed. Just before Evan joined me we got a call by VHF from a boat anchored across the Sea in Guaymas—he let us know they had just been nailed by a Chubasco and that it was coming our way.

Around 11pm we were woken by chilly rain drops that felt as big as robin’s eggs. When a storm is strong enough, it blows out big rain drops, not the little ones associated with a typical approaching rain. Evan popped his head out the forward hatch and discovered that not only was the sky bright with lightning but a wall of rain was headed our way.

We both jumped up and went through the motions of preparing for a storm—I turned on the motor to relieve stress on the anchor in the gusts. And Evan closed hatches, got our instruments on, and lowered our lightening grounding system. Then he took over the wheel and I put as many of our electronics as would fit into the oven and then put the overflow into the pressure cooker—basically creating a low-tech Faraday Cage. (Check out this great article on lightning protection for tips and ideas.)

By now we had a steady 25-30 knots of wind. By Chubasco standards this was a small blow. What we had though was a lot of nearby lightning and cracking thunder. I took solace in the fact there are some tall mining structures near us (and a very tall mast on S/V Third Day), making it unlikely we’d take a direct hit. As the wind let up, the heavy rain continued—it looked like all that would happen in this blow is we’d get a good boat clean.
post-chubasco lightning--not as dramatic as mid-chubasco lightning, but we were busy then
After an hour, conditions eased and the storm seemed to have passed. But we were still seeing lots of lightning out to sea. When we fired up the computer, we discovered all we experienced was a very small cell that had broken off the main one—and that the huge area of convection that stretched from the mainland and ¾ of the way across the sea was still to come. Our guess was if that cell didn’t break down, we would be hit much harder within the hour.

I called the other boats in the anchorage to let them know the bad news (so they wouldn’t be caught off guard by a second storm). Then we waited, and waited. I dozed off and Evan later fell asleep while reading. The storm dissipated and as much as, ‘and nothing happened next’ doesn’t make for good story telling, it does make for good cruising…


ellen said...

Just caught up on your summer adventures! Bahia Conception brought back my memories of a NOLS course there ten years ago. Such a beautiful place- all the best for few chubascos and a brilliant fall season!

Diane, Evan, Maia and Charlie the cat said...

Thanks for popping back in, Ellen. It's always fun to know who is reading. Your adventures on the ICW bring back memories too. I remember really enjoying the Great Dismal Swamp...