Sudden Trouble

[Stillraining]

Originally Posted by CharlieCobra

Ok, you've been beating westward into a forecasted Cold front that's supposed to hit at 3PM with winds to 30 knots. It's been cloudy and about 50F with Southerlies @ 15 knots. It's around 5PM and you can see a nice dome of blue to the West and you and your partner decide it's time to head back home. The wind has clocked around to the WSW and is blowing about 5-8 as ya rig the A-sail. You turn off, hoist the Assym and get ready to pull the scoop to release when a massive gust of over 40 knots hits. The endless line comes loose, is out of reach off the deck and the chute suddenly opens. The boat lays completely over on her side and puts the main and mizzen in the water while you step from the deck to the side of the mast while hangin' onto the shrouds. You look back at your helmsman who's laying on the side of the cockpit, inches above the water yelling "What do I do?" over and over while moving the tiller back and forth uselessly. The house is wide open but staying dry. What do ya do now?

You pull the boat out of the water and find a barn to store it in...

[s/v Beth]

Now that we're sharing knockdown incidents- Was out on a large freshwater lake with my Compac 23. Five people on board (only 2.5 sailors) first mistake. Went out in 20 knt winds because we wanted to sail so bad- second mistake. Winds went from 25 to 60 in less than a minute- had reefed main and jib up- tried to point into the wind (so we could drop the sails) but the wind overpowered that little boat and it went down. My son in law ran on the side of the boat ( which was now the horizontal surface) up and pulled in the reefed jib. I let out the main sheet and we popped back up in a minute or two. In the meantime the rest of the crew was in horror. Not a pretty sight. Who says we don't need drogues inland?

[Brent Swain]

A forecast cold front is a warning that it's about to blow like hell. Drasticaly shorten sailt at the first sign of it, then re set sails after it has passed.Got caught that way once. Now I take my time and wait for it to pass.
Brent

[GordMay]

A Cold Front is defined as the transition zone where a cold air mass is replacing a warmer air mass. In North America, cold fronts generally move from northwest to southeast.

The air behind a cold front is noticeably colder and drier than the air ahead of it. When a cold front passes through, temperatures can drop more than 15 degrees within the first hour.

As a cold front arrives in a particular place, the barometric pressure will fall and then rise.

The wind veers with frontal passage and is often strong, gusty, and turbulent for a considerable period of time after passage.
In North America, winds ahead of a cold front tend to be from a southerly direction (south-southwest), while those behind the front (in the cooler air) tend to be northerly (west-northwest). In fact, weather stations use the shift from a southerly to a northerly wind direction as the indication that a cold front has passed the station

Cold fronts are typically accompanied by a narrow band of showers and thunderstorms.

The speed of the movement of frontal systems is an important determining factor of weather conditions. Rapidly moving fronts usually cause more severe weather than slower moving fronts. For example, fast-moving cold fronts often cause severe prefrontal squall lines that are extremely hazardous.

[s/v Beth]

GordMay,
Thank you for the very correct weather- but sometimes, like what happened on Utah Lake on Labor Day, there is no warning. No movement of Barometer, no warning on WX (I know, I check each time before I go out) No change even of the cloud structure (overcast about 5000 feet above us). I think we had about 1 minute warning seeing a change in wave structure (the tops of the waves were being blown off as the microburst came across) but even that was hard to see until it was upon us.
Not trying to scare anyone.
Not trying to make excuses...
Just saying it happens and you better be prepared before.

[GordMay]

Like many people, I know very little about downbursts.

Any strong winds coming down from showers and thunderstorms (convective storms) are known as "downbursts." If damaging winds are concentrated in an area extending 2.5 miles or less, it's called a "microburst." If the winds cover a larger area, it's a "macroburst."

A downburst is predictable for only a short time span, and greatly enhances winds already being produced by a convective storm. This means that within a moderate storm, a sailor can be surprised by sudden high wind speeds. But they don't always appear when stormy weather is forecast. Microbursts can even occur suddenly, when there's rain, but no thunder and lightning.

Microbursts are capable of producing winds of 30 to 120 knots, causing significant damage. The life span of a microburstranges between 5 to 30 minutes.

A great variety of environments can produce microbursts. Of particular interest are two extreme types in which microbursts can occur in large numbers. One is the extremely dry environment in which moist convection is just barely possible, and the other is the extremely wet environment, which can produce microbursts embedded in very heavy rain. In the humid East, "wet" microbursts are most likely; while "dry" microbursts occur more often in the West.

[s/v Beth]

Do you guys get horizontal rotary winds like we get here in the Rocky's? They have recorded winds out here in Utah (on the Great Salt Lake) at over 200 knots. They come behind lenticular clouds, and whenever I see such, I don't sail. They have been described as horizontal invisible tornadoes. Whenever a big plane goes down in Denver they usually get the blame.
BTW thanks Gord for the explanation of micro bursts. I have seen em, been in them but did not know about the dry and wet types.

[Stillraining]

Originally Posted by newt

Do you guys get horizontal rotary winds like we get here in the Rocky's? They have recorded winds out here in Utah (on the Great Salt Lake) at over 200 knots. They come behind lenticular clouds, and whenever I see such, I don't sail. They have been described as horizontal invisible tornadoes. Whenever a big plane goes down in Denver they usually get the blame.
BTW thanks Gord for the explanation of micro bursts. I have seen em, been in them but did not know about the dry and wet types.

Newt

I have never heard of thoes ..but then again my wife tells me I dont listen real well either.

[GordMay]

If you ever see a cloud, generally over a mountainside, which looks like a flying saucer or a lens, you're looking at a Lenticular Cloud - technically Altocumulus Standing Lenticularis, or ACSL for short.

See the “Colorado Weather Almanac” ~ by Mike Nelson
Colorado Weather Almanac - Google Book Search

[Stillraining]

We do indeed get lenticular clouds...been in them actually as i use to climb high glacial peaks...they are a sign that winds are in excess of 60 mph...still I have never heard of rotary winds referred to here in the PNW...

[s/v Beth]

These rotary winds are primarily a danger to planes. We get them here, but I don't know if they affect us on the lakes. Maybe I am overreacting to not go out when I see lenticulars, but we are often a superstitious bunch. (sailors) What I do now is we get very violent short lived high winds out on our lakes and I respect them. I would be interested to know what other sailors do in these little nightmares.

[CharlieCobra]

Sheet out and hang on...

[bruce in oz]

cruising up the qld coast, had a beautiful break at fitzroy island, replaced a lost anchor & chain, took on fresh water, enjoyed a walk ashore, bare breasted tourists etc. then sailed across to mission bay near cairns, no need to go into cairns, stayed away from it. left mission bay heading north 20kn se off starboard, nice cruising, too captivated with the coast, the rocks, the beauty,**** i'm heading straight for those rocks, i could spit on them, what do i do... help god. terrified (chortle chortle, not for the first time) i let everything go, god and the yacht had more sense than me, it immediately veered to starboard and cruised away from the rocks, whilst i'd been knocked down and knocked off previously on the voyage it was the closest i had come to actually destroying the yacht.
lesson learnt, when i got a bit further north to the most magnificent cape melville granite boulders i stayed well clear of them and immensely enjoyed the cruise across the bay to the flinders island group, sitting in the cockpit as the sea-cows came along for a look or splashed their tails and filled the cockpit with water

air supply sing a beautiful yachties song, faith


(Chorus)
I have faith
In your love
I have faith
In your heart
You don't need to hide from what you want
You've just got to give it all you got
The first thing that you need
You got to have faith

now, i'm sitting in the beagle gulf, looking at the biggest full moon we will see this year in the southern hemisphere, the fresh water tanks are full because its been raining all afternoon, my satellite internet credit is just about bust but i've still got a bottle of dodgey sadgroves creek butterscotch schnapps and a hell of a lot of faith, love my boat....

[CharlieCobra]

Now THAT sounds like a good time.

[gonesail]

a forecasted cold front that's supposed to hit at 3PM with winds to 30 knots? and you are hoisting a light air assym at 5PM? guess you won't try that again