February 21, 2005

Wall Clouds

Study the following photos closely as they could save your life. These clouds, as a minimum, will be carrying winds of 30-60 mph and can gust much higher. They can spawn a tornado. I've been caught on the water 3 times as one of these approached - twice I was lucky enough to make it to shore, and a third time I made the mistake of listening to someone else.

They can be long or short, but the primary characteristic is they will be traveling under the main cloud base at high speed. Winds can last 15-20 minutes and are sometimes accompanied by hail.

Don't underestimate these winds! I once made it to shore to seek cover when the wind came up and whipped my kayak off shore and blew it back in to the water. Use your painter to tie the kayak to something substantial before taking shelter.

If caught out on the water, your best bet may be to wet exit and hide under the cockpit of the upturned kayak before the winds arrive _if_ there is not a lot of fetch to build up large waves. This will help prevent you from getting knocked over and losing your kayak when you wet exit in the storm as well as protect your head from hail. You may want to think about using the painter as a tether.

Time is of the essence. When you spot one of these head toward the nearest cover as quickly as you can. If you are lucky you may spot this 5-10 minutes before it arrives, but most likely it will only be a few minutes away when it catches your attention. These clouds will move very fast so don't think - just do. As you begin to feel the winds know you only have a few seconds to decide what course of action to take.

Woody

After writing the above, some folks posted their experiences with wall clouds in the CPA list server. Reproduced here with their permission, you might gain some valuable insight into dealing with these high winds.

From Mike Vandamm:

About 7 years ago while crossing the mouth of the Magothy solo on a
bright summer's afternoon with a "very slight chance of a thunderstorm", a solid, almost black wall cloud very suddenly towered up in the western sky. I was about a mile and a half from the nearest beach, and the same distance from the Baltimore Light. Thinking that the beach, which was largely bulkheaded, would offer little shelter, I sprinted for the southeastern side of the Light where, in a V-shaped pocket of water slightly longer than a kayak, keeping my bow within inches of the base of the Light with vigorous forward paddling, I survived for about 20 minutes while winds up to 73 knots (measured at the Thomas Point Light a few miles to the south) and a rapid train of steep 3-4 foot waves whipped around the Light. Baltimore and Annapolis were blasted by the squall line but the D.C. Metro area learned about it only on the evening news, indicating that the weather event originated in the few miles immediately to the west of the Bay.

Experiences like mine are not exactly commonplace on the Chesapeake, but the Law of Large Numbers suggests that a low probabity event repeated many times will eventually yield an interesting trip report.

Mike Vandamm

From Greg Welker:

I got caught by a small one of these doing a short crossing of the Potomac several years ago. It got me about 1/2 mile from the downwind shore. Not seeing large waves as part of the wind, I put the boat perpendicular to the wind, extended my greenland paddle out into an low brace on the WINDWARD side so that it was buried about 1 - 1.5 feet below the water surface, and bent forward over the paddle to lower myself toward the boat. I then leaned the boat into the wind. This worked well in giving a stable position, but I had to make sure the paddle stayed under the surface as it acted as a drogue to keep me from being blown over.

I would not try this method in large waves.