SailNet is a forum community dedicated to Sailing enthusiasts. Come join the discussion about sailing, modifications, classifieds, troubleshooting, repairs, reviews, maintenance, and more!
What does "Chance of Thunder Showers" really mean?
I sail in Lake Ontario on a Hunter 36, based in the Outer Harbour Marina in Toronto. This is my first full season of sailing. This past weekend my wife and I made the 25 NM trip south across the lake to Niagara-on-the-Lake for an overnight stay. We had beautiful weather both ways (although a little more wind would have been nice).
We almost didn't make the trip because the forecast was calling for "Chance of thunder showers" for most of the time we would be sailing. I checked the Environment Canada radar before each crossing and everything looked clear, and as it turned out everything was fine. But those forecasts made me very nervous and had me constantly scanning the skies for approaching thunderheads (which never materialized).
How dangerous is it to be caught out on Lake Ontario if a thunder storm does develop? I'm fairly confident in my ability to handle the boat in the rain/wind/waves that might be encountered (assuming I have enough advance notice to get the sails properly reefed or even dropped completely). How worried should I be about lightning?
How seriously should I take warnings of 'chance of' thunder showers/thunder storms? Did I just get lucky over the weekend? What sources of weather forecasts are reliable in my area? I check the Marine Forecasts for Lake Ontario, and use the Environment Canada weather radar. Most of the 'possible thunder shower' warnings were coming from The Weather Network, it occurred to me that maybe they are very 'conservative' with their predictions, preferring to predict possible rain and have the weather turn out to be nice than the other way around? That seems generally sensible, but it almost cost me a very nice weekend of sailing.
I would imagine that if you like playing the odds, it would go something like this: Say there was a 30% chance of thunderstorms. In ten trips across the lake you would get nailed in three times. Of those three, maybe one would be no big deal, and one would be hair raising. Having the skills and a boat that can handle most any wx (short of a long November gail, or the Chi-Mac storm) would make me comfortable.
On the Chesapeake (and at my house in PA), I've noticed that if the forecast is 50% chance or below, we probably won't get rain, but I keep an eye out. Anything above that and I take it as a definite and plan accordingly.
I've never sailed on any of the Great Lakes but my understanding is that storms can be extreme. I would suggest that you start paying attention to the weather (at home and at the boat) as a normal part of your day, not just when you want to go sailing. Learn the prevailing winds, how the environment changes leading up to a storm. Think about it until weather becomes second nature to you.
Three days before a planned trip, even a day sail, I start looking at the weather. In the northern hemisphere most systems move west to east. So if I see a storm tracking across the upper midwest, it may be strong enough to keep moving towards the mid-atlantic without breaking up. I keep an eye on things until I leave the dock and then every so often I'll listen to the marine forecast while I'm on the water. The Chesapeake is notorious for summer squalls.
A good barometer is also a handy thing to have on board. It's not just falling barometric pressure that you have to watch out for, but how fast it falls. Quickly and something's up.
Sudden change in wind direction or temperature sometimes means a front is nearby.
Get a good weather book or take a class to learn how to read the weather. It could save your life someday no matter how much you think you can handle your boat in a storm.
Heavy Weather Sailing by Adlard Coles is popular and there are others. I think the Pardys wrote a book on sailing in heavy weather. I have their video on the subject.
In the end, if my gut says don't go, I don't go. I try to be educated enough to know what to do should I get caught in a storm, but many times I've made the decision not to go and sat at the dock listening to maydays on the radio. The few times I did go, I had a miserable sail. Others will disagree and love the challenge and excitement, but I prefer to have my boat and myself and family around to sail another day.
I sail in Lake Ontario on a Hunter 36, based in the Outer Harbour Marina in Toronto. This is my first full season of sailing. This past weekend my wife and I made the 25 NM trip south across the lake to Niagara-on-the-Lake for an overnight stay. We had beautiful weather both ways (although a little more wind would have been nice).
We almost didn't make the trip because the forecast was calling for "Chance of thunder showers" for most of the time we would be sailing. I checked the Environment Canada radar before each crossing and everything looked clear, and as it turned out everything was fine. But those forecasts made me very nervous and had me constantly scanning the skies for approaching thunderheads (which never materialized).
How dangerous is it to be caught out on Lake Ontario if a thunder storm does develop? I'm fairly confident in my ability to handle the boat in the rain/wind/waves that might be encountered (assuming I have enough advance notice to get the sails properly reefed or even dropped completely). How worried should I be about lightning?
How seriously should I take warnings of 'chance of' thunder showers/thunder storms? Did I just get lucky over the weekend? What sources of weather forecasts are reliable in my area? I check the Marine Forecasts for Lake Ontario, and use the Environment Canada weather radar. Most of the 'possible thunder shower' warnings were coming from The Weather Network, it occurred to me that maybe they are very 'conservative' with their predictions, preferring to predict possible rain and have the weather turn out to be nice than the other way around? That seems generally sensible, but it almost cost me a very nice weekend of sailing.
As I understand it; A 30% chance of thunder showers means that there is a 30% chance that any one place in the forecast area will be hit by a thunderstorm. In other words, the thunder showers will most probably be out there, but, there is only 1/3 of a chance they will come over you.
I also look for the marine forecast that says high wind, dangerous lightning, hail, or waves that will be X% higher than predicted. That stuff often comes with small craft advisories.
A smart phone is a big help. I use Wunderground.com
As for getting struck by lightening, I'm in Fisher's Island Sound, CT. so I don't know if being in fresh water is a factor. I have a keel stepped mast and getting anywhere near it in lightening makes me nervous, to say the least.
Then again, sailors drown, get run down by power boats, get hit in the skull by a boom, and do untold damage to their livers every year. I have yet to read about one getting hit by lightening. Sailboats yes, sailors?.... so, of course, I get the bright idea to google it...
As I understand it; A 30% chance of thunder showers means that there is a 30% chance that any one place in the forecast area will be hit by a thunderstorm. In other words, the thunder showers will most probably be out there, but, there is only 1/3 of a chance they will come over you.[/url]
I've also heard it explained as under these specific meteorological conditions, the event (rain/snow/thunderstorms) will occur X% of the time those conditions exist.
The Great Lakes are not to be taken lightly. Have seen or heard of the recent tragedy in the Chi/Mac Race?
We routinely sail longer distances on the Great Lakes. If we have a trip planned and there are scattared showers amd thunderstorms, we generlly take our chances, but than again, we have many years of experince under our belts. If we are on our marina and simply want to go out for a day sail and there are thunderstorms in the area, we probably stay secured to the dock.
Tommays gave you a fine example 5 knots to 40 knots in a matter of minites.
You also received excellant advise from DRF. Make sure you and the boat are preparred everytime you go out. You never know what might happen.
Living in VA Beach between the ocean and the bay we have a chance of showers everyday during the summer. So I have taken "chance of showers" to mean because the heat from the pavement is going to cause a sea breeze and the subsequent drawing of moister into the air, there's a strong possibility that we will have showers at the end of the day. And we typically do. The question becomes where, for how long, and how severe. Hence the common reference to bay squalls that last for 10 to 15 minutes.
I would think living on Lake Ontario you get the same. We typically do not pay much attention to it unless there is a storm front that is moving our way from elsewhere.
I have a theory about Chance of Rain. I've noticed that our weatherpeople seem to use Chance of Rain/Thunderstorms much more often than in the past. I've concluded that if there is even the slightest chance, they now will say 'Chance of ...' whereas before they would say "Partly Sunny" or something like that. I believe that is because when they said "Partly Sunny" but it rained, people were upset with them. If they say "Chance of Rain" AND IT DOESN"T RAIN, people are happy. And they come out looking more like winners even though they are still wrong.
As the weatherman says: Tomorrow, the weather will be either sunny, raining, stormy or blizzard, it all depends on the weather. Just be prepared and have Plans B and C ready.
If for day sail, I seldom pay much attention until the hour I set sail. Just get a mental picture what is weather pattern looks like. i go out regardless. A proper sail area is the key, be prepared to duck into a safe harbour or sail to an open area.
My son and I used to love to sail our 14.2 ft Catalina in 20 to 30 kn storm with horizontal driven rain. We almost turtled her every time. It is good that it was not like a Hurricane, we knew that the storm will only last half hour, we just have to hang on to the boat. . Learning how to prepare and practice the prudent task improve our survival skills in the big pond.
I once had a captain that I was crewing. He dodged the rain clouds every 20 minutes. We were in a moon lit sky and not much wind. Everything we tacked to avoid the black clouds, the jib was caught between the mast and staysail. I had to get up the bow and fix it. After the fifth times, I asked if his boat will melt when the rain hits.
I hate to challenge the captain. But sometime it is necessary to conserve my energy for the unpredictables.
Around here " Chance of" usually means go sailing. I've been watching their language for a long time. When they upgrade to " Likely" I will take additional notice.
As has been noted, usually just about everyday in the summer, we'll get a "chance of" rain and or thunderstorms. The risk is higher in the evenings that something could happen...more often than not, you can get where you're going..or get a good sail in before anything happens.
Sounds like you did exactly the right thing. Any four or five hour passage should be easily handled with a quick weather briefing prior to departure.
The Chi-Mac tragedy has been referenced a few times, but that isn't entirely comparable. First, that is a 300+ nm race, which is much harder to predict. Secondly, the boat that foundered had a handicap with the extended wings.
In any case, one should practice heaving-to or have other storm preparation ready to go. Most T-storms will move over in less than one hour, often much less.
The good news is that between Toronto and Niagara -On-The Lake there are any number of harbours to duck into. If the weather looks iffy, always have a handle on where the nearest port of refuge is. Don't be afraid to be prudent. Plan your refuge when you see black clouds and rain in the distance, not when it is over your head and hitting you horizontally at 40 knots.
"chance of" really means "We don't know where they're going, it could be here."
Or as the sailors say, a crapshoot. How lucky do you feel?
The real problem isn't the thunder or the showers, but thunder means there will be lightning, and "chance of being struck by lightning" is what would bother me.
that's when you have to pop your head up and make your own decision. How does "a crapshoot on getting fried" sound? Better or worse than "chance of thundershowers" ?
Yeah, but they probably couldn't say it that bluntly on the radio.
Thanks for the responses everyone. A few comments:
Bljones: I'm not sure what route you would recommend between Toronto and NotL, but the route I took was almost due South, straight across the lake. For the first half of the journey, the closest port is to turn around and go back to Toronto. For the second half of the journey, the closest port is to keep going to Niagara-on-the-Lake. So I didn't have any 'safe harbours' to duck into. I guess you could sail around the western edge of the lake, but that would at least double your distance and travel time, turning a 5 hour crossing into a 10 hour trip. Is that what you're recommending?
I agree with the comments that you should be ready to handle the conditions you're likely to face before going out. If I'm not ready to handle 45 knot winds if a thunderstorm strikes, I shouldn't be out. I think I need to work my way up to that sort of wind, although I've been out on days with 35 knot gusts, I wasn't exactly comfortable.
I'd like to hear more about lightning strikes. This is what was really concerning me. Rain could be uncomfortable, and very high winds are potentially dangerous if not handled properly, but the chance of getting hit by lightning was what was really freaking me out. If you do get caught in a thunderstorm, how likely are you to get struck? Are you any safer sitting back at the marina? What do live-aboards do when a thunder storm rolls through? I suppose at the Marina at least there are lots of other masts for the lightning to hit instead of your own, but is that good enough?
If a boat does get struck, how disastrous is it? I expect your electronics would get fried, but are those aboard likely to suffer injuries? Is the boat likely to be damaged structurally, and possibly risk sinking?
I'd like to hear more about lightning strikes. This is what was really concerning me. Rain could be uncomfortable, and very high winds are potentially dangerous if not handled properly, but the chance of getting hit by lightning was what was really freaking me out. If you do get caught in a thunderstorm, how likely are you to get struck? Are you any safer sitting back at the marina? What do live-aboards do when a thunder storm rolls through? I suppose at the Marina at least there are lots of other masts for the lightning to hit instead of your own, but is that good enough?
This thread has some food for thought regarding lightning.
I attended an SSCA marine insurance workshop and the speaker said that catamarans have the most claims for lightning in the industry. Might want to sidle up to one in a storm.
I think if you ask four people about how to protect a boat, you'll get three different answers.
The general forecasts are not worth much to someone in Thunderstorm County trying to determine if they can go out for a daysail.
The daysailor needs a precise forecast for a very small area. General forecasts are near worthless the daysailor
One needs to learn to use the raw data (radar maps, iso bars, lightning strikes) to develop a precise forecast for one's own small area. It takes a few years, but after a while, one can be very very accurate.
It is also part of good seamanship to have some modicum of understanding of weather forecasting. A good book is 'The Sailors Wind" by Stuart Walker, it focuses on round the bouy racing, but has an enormous amount of information for the daysailor.
I usually watch the weather before setting sail. if there are no storms in the "viewing area" then i head out. I always keep my eyes on the sky and keep my storm gear handi. I would never go sailing if i stayed in with a chance of thunder shower here on the lower Chesapeake. I will say i have been very lucky so far. i imagine its only a matter of time before i get caught, hopefully my planning and practice will be enough!
Well it happened yesterday, took a nice day sail out to Cape Henry light house from Little Creek. Wind was great 10-15knots clear blue sky, forcast slight chance of t-storms in the evening. We headed out at about 1pm and reached the Cape Henry Light house by 2:45pm. As we were approaching the light house i looked behind and saw the ominous sky. I immediately double reefed the main, we only have the 100% jib on. as the storm approached i was real nervous because of all the anchored tankers and commerical traffic in the area. we kept sailing toward the light as our cell phone radar indicated the storm would stay in the bay and it did. We maybe saw gust to 25 and all seemed well. Wind died down to about 10kts so we put the main completely up and changed the head sail to our 140% we were making great time back as we passed back through the tunnel at about 4:30-45 the wind started kicking up again. much stronger this time 15-20knot with gust to 25kts as we were about 2miles from Little creek, wow all of a sudden all hell broke loose. I say all of sudden because there was no dark clouds, no rain, slightly overcast....we immediately dropped all sails and started the motor. within 3-4 mins winds were blowing a sustained 35kt with gust to 40+(verified later by bouy data). Wife and I donned our life jackets as we were taking spray and wave over the bow. we were making almost no head way directly into the wind and waves so i decided to go at a 45 to them we started to make head way but we were getting broadsided by the chop and getting wet!!!!!! we kept motoring for the next 20-30 minutes into this mess and just like that, wind was 10knts. when we made it to the entrance to the channel it was almost calm.
We docked and everyone was safe. Although there were a few other boats that did not fair so well. A few boats at our marina(out sailing) lost sails, one went aground that was anchored by our marina. One of the crew of the boat that lost his sails said they saw 50kt wind with gust to 60 according to their instruments....
All in all, an experience we needed. Our boat never felt unsafe but Jacklines and tether have now become priority #1, when we reef lifejackets go on when a storm is near or approaching! ......although Hurricane Irene just bumped into #1 today.
Somewhat off topic, but on the subject of weather, I liked this piece from this morning's SMH ...
Yesterday's item about the peculiar subtitling of TV weather forecasts reminded Des O'Brien, of Manly, of ''a wonderful BBC weather forecast I heard years ago. The announcer predicted 'showers so frequent as to amount to almost continuous rain'.''
Weather patterns not so much different here on Long Island Sound, and I've become used to checking the animated radar maps on Web sites like AccuWeather or WeatherUnderground. They're highly accurate, and you can SEE a cluster of red-centered clouds comin' at ya, usually in time to duck (or stay in port).
So I recently bought a 3G USB modem for my laptop, and now take it aboard for overnight trips. Works great! And the pay-as-you-go plan (from Virgin Mobile) lets me buy megabytes in $10/10-day clusters, so I'm not paying for a connection in the non-sailing season.
here on the Barnegat bay storms come from a general west direction and when they do they spring up fast on the radio and radar. learn the weather patterns for your area and compare them to the published weather. i know when i see tall anvils on clouds and something is approaching from the west its time to head in or hunker down.
Watch the maps that show the storms in motion, then predict their track based on their current movement. Usueally they are moving pretty straight, sometimes they curve as they go, so you can extrapolate the curve. Also look for the center of curving storms (the Low) and how that low is moving.
My wife and others call me to know the exact time rain will start. I measure on the screen the distance covered by the 2-hour-motion-loop and then give them a best guess, precise (not necessarily accurate) to 15-30 minutes.
You can also see thunderstorms popping up over the course of the 2 hour loop. Those are the ones that are hard to predict.
By the way, I've recently found intellicast to be perhaps a bit inaccurate compared to ground observations and so started using other radar sources.
I just compared intellicast to another site, and intellicast didn't show a storm that went right by the boat. That's all. Maybe there was a bug in the system that day.
Regards,
Brad
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
SailNet Community
1.7M posts
173.8K members
Since 1990
A forum community dedicated to Sailing, boating, cruising, racing & chartering. Come join the discussion about sailing, destinations, maintenance, repairs, navigation, electronics, classifieds and more