Mid-West Thunder Storms

[BudGates]

I’ve mentioned before that my wife and I will be moving to her home state of Minnesota when I retire next July. Lightning makes me nervous when I have an aluminum pole sticking 30+ feet in the air. I’ve been watching the Minnesota weather forecast for the past couple of months and it seems to predict thunder storms about 3 days a week. Is this normal for the Midwest this time of year? I would ask my wife but she moved away 40 years ago when she joined the Navy so her memory may not be all that reliable. Since I will be retired I should be able to schedule my sailing around the weather but I’m wondering what most people do. Do you heed the forecast and stay off the water, even if it looks fine, or do you go out when it looks good keeping an eye on the sky and head for shelter if it looks threatening? What about keeping your boat at a marina? Do you worry about lighting strikes when the boat is left unattended or am I being overly cautious?

 

[David in Sandusky]

There are two kinds of thunderstorms:

1. Systematic storms, usually associated with a cold front, and or a low pressure system. They are described in weather forecasts, and a radar app on my phone allows me to pin down when they will arrive.
2. "Pop-up" thunder storms develop anywhere on hot summer days, usually after 4 PM on Lake Erie, and usually on the shore line

So we get to, and stay in a safe harbor when storms are expected. A safe harbor is a marina, or an anchorage that is protected from storm wind and waves. Nearby boats with higher masts, or a hill with trees on it are pluses for lightning protection. Our mast is grounded to our keel, and we have a second grounding cable that we can rig to our mast and toerail. Itexposes a square foot of bare copper cable over the side to the water at anchor.

Unlike ionized salt water, fresh water is not a good path to ground for lightning, making a strike on a sailboat very unpredictable and less likely on fresh than salt water. The mast and associated standing rigging form a cage around the boat and its crew, offering important protection if the boat is struck and if you stay inside the cage, and away from the mast and shrouds. In the event of a strike, however, its field effects and side currents will probably fry all of your electronics. This has happened to a few acquaintances, usually those with the taller masts. With much lower frequency, I have also heard of side spurs from the mast grounding system punching holes in the hull and opening it to flooding.

In 17 summers and around 400 cruising days and nights in a sailboat, we have never been caught at sea in a full blown thunder storm (although we have had three close calls.) We have taken reasonable precautions, and have weathered a number of storms at anchor or moored as well as in marinas. We have contingency plans if we were to be struck, but have never had to use them.

Good luck! Enjoy your sailing around the storms that will come!

 

[Jackdaw]

While we avoid sailing in thunderstorms on Lake Minnetonka, I never ever worry about storms when I'm off the boat. It's so very rare an event (a boat hit) that I just pay my insurance premiums and never think about it.

 

[BudGates]

Thank you Gentlemen. I feel a little more comfortable now. I will be sure to check the forecast and keep an eye on the sky while I'm sailing, but I won't be quite so concerned about the boat when it's in the slip. I learned to respect thunder storms when I was stationed at Camp Lejeune NC. (Yes, I'm a Marine and my wife was Navy.) We had one storm that had lightning crashing all over our yard. There wasn't even any delay between the lightning FLASH and the thunder BOOM. One flash hit our TV antenna and fried our color TV. (Color TV was a luxury back then. lol) The storm only lasted about 30 minutes but I'd hate to be caught outside or especially on a sailboat when it hit.

 

[DougM]

Its August and hot, so pop up thunderstorms are inevitable. Our place is on the east shore of Lake Michigan, and we have learned that if a little black ribbon of clouds appears on the western horizon, its time to get off the lake (sometimes it's almost too late). Fortunately, when the lake water is cold, it takes some of the severity out of the weather. The storms come on shore and reintensify about five miles inland.

 

[walt]

In all the years I have been watching this stuff, there has only been one fatality that I have heard of and I think it was up somewhere in the area you are going to. A family was in I think an old Mac 26 Classic and a storm hit and they beached the boat bow first. Everyone got off the ladder in the back and waded to shore. Lightning stuck somewhere (dont know exactly - I dont think it hit the boat) but a young kid was about waste deep heading from the ladder to shore and was killed by the strike. In fresh water.. the conclusion would seem to be that being in shallow water near the boat during a storm is definitely a bad idea.

You sleep in the aft berth on that boat so dont have that nice big ol 28 foot conductor above your head.. Chances are you will never get struck.. but being in that back berth definitely helps you sleep better.

 

[Jackdaw]

As for weather WHILE sailing, we look at real-time weather apps on days where based on temp and humidity it might 'blow up'. Best apps show past true as well as future predicted. You can pretty much watch it roll in. And know when to get off!

 

[plenny7]

I've done no tracking of the forecast, but thunderstorms predicted 3 days a week seems a bit high for Minnesota. If I had to guess what the true number is, it'd be more like 1 day per week. I would expect, however, that the predicted number is greater than the true number, particularly if you're including days with a low percentage chance.

Keep an eye on the forecast, on the sky, and in your smartphone app and you'll be fine. If you look at the 5 year Flash Density Map you'll see that Minnesota is not a high lightning density area.

http://lightningsafety.com/nlsi_info/lightningmaps/US_FD_Lightning.pdf

 

[Jacktar]

Good advice, watch the sky, watch the apps and head in or away when stuff appears.

 

[Benny17441]

Statistically I would be more concerned about hail and high winds than lightning strikes.

 

[Jumpstart]

Sometimes you are too far offshore to get in. Worst lightning storm I've ever been in was 2011 Chicago Mac race. 2 fronts meet over the Manitou passage and the lightning was unreal. Flashes were constant. Video doesn't do it justice but remember video shot in the dark so what you are seeing are images caught in the flashes. Also noise was more than video shows. Storm lasted for 40 minutes with winds ramping up to the 70 knot range for a time and then poof it was gone.

 

[JamesG161]

The mast and associated standing rigging form a cage around the boat and its crew, offering important protection if the boat is struck and if you stay inside the cage, and away from the mast and shrouds.

If, and only IF, you mast and rigging is well grounded to the water.
Check this link! My post #5 has an attachment about lightning protection from a great book by Nigel Calder.
http://forums.sailboatowners.com/index.php?threads/newbie-lightning-protection.179404/
Jim...

 

[Roadking Larry]

Lightning is gonna hit where it is gonna hit.
In the last 2 weeks two sailing friends of mine have had their boats struck by lightning. One here in Oklahoma and the other down in Florida.

 

[Benny17441]

Lightning is gonna hit where it is gonna hit.
In the last 2 weeks two sailing friends of mine have had their boats struck by lightning. One here in Oklahoma and the other down in Florida.

Larry I'm curious where the boats out in the water or were they docked at a marina? I have been looking at statistics that tend to indicate that the majority of lightning strikes occur near land as opposed to out at sea. It is actually a rarity for a sailboat to get struck out at sea. Fortunately I have not heard in years of any fatalities due to strikes. There is really very little that can be done as like you say "ligntning is going to hit where it is going to hit". They say bonding helps attract lightning but lessens the damage in case of a strike; it don't sound to me like a fair exchange. I am beginning to think there is something to the theory of the "cone of protection" where there is an imaginary cone originating at the top of the mast with a diameter at water level of the same length as the mast. Conclusion, due to the statistics I,m not afraid to go out in a storm and feel a little better when I get away from land.