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Old 01-26-2010, 12:30 AM   #1
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Greetings,

Does anyone know where I can find authoritative guidelines and safety precautions for the avoidance … confrontation ... and survival of powered and sailing vessels caught in acute SQUALL situations at sea.




In this context, “squall” refers to: frontal and isolated squalls, squall lines/line squalls, microburst/downdraft events, white squalls, derechos, bulls-eye squalls, etc.



A parallel focus will be to differentiate one from another as some confusion seems to exists here.



Direct assistance ... and promising links ... will be most appreciated.



Many thanks.
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Old 01-26-2010, 02:04 AM   #2
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Hello and Welcome to Cruiser Log,

Generally speaking squalls in the daylight hours give some time for the cruiser to prepare the boat for the passage of the squall (or storm) Understanding that gusts during the squall can easily achieve 60 knots and it is the sharp arrival of a gust during a sustained wind of say 35 knots that can do the most damage. First thing to do is to alert all on board to be on their planned stations. Present day sailing boats with their jib furling systems should be one of the first items to be thoroughly secured (unfurled = chaos!) then, all unsecured items in lockers or below decks. Main sail reefed right down. Engine started, boat turned into wind. Once all obvious preparations have been made - give the engine sufficient RPM to hold a steady position.

When the boat is moored or secured at anchor in an anchorage with other vessels then extra preparation is required - consider leaving the anchorage and head out to sea. Otherwise take a bearing on your position to ascertain if you are dragging. check the positions of other boats relative to your own and the approaching squall.

There is nothing like PREPARATION in good time.

Here are a few links in Cruiser Log.

Squalls

http://www.cruiserlog.com/forums/index.php...5&hl=storms

Read the special Navigation Notes in this one

http://www.cruiserlog.com/wiki/index.php?title=Portugal
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Old 01-26-2010, 08:02 AM   #3
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Quote:
Originally Posted by MMNETSEA View Post
Hello and Welcome to Cruiser Log,

Generally speaking squalls in the daylight hours give some time for the cruiser to prepare the boat for the passage of the squall (or storm)
Totally agree with everything there Mmnetsea - another good tell tale is a drop in the barometer and the sudden apprehensive look on your good lady's face.

Seriously though, we found our radar absolutely fantastic in helping us dodge around squalls both in daylight and more particularly at night. Set at our full 25nm range with gain calibrated for rain and high definition we were able dodge around many squalls on the way to and back from Vanuatu and New Caledonia. Having never used the 'rain on' setting prior to our blue water and still wading through the instructions when we left Brisbane, we had mainly used it to alert us to other vessels. Discovering that it could also track squalls and fronts barrelling down on us was a significant comfort and more importantly, safety factor for blue water first timers such as us.

We have a Raymarine C80 radar and chartplotter. Next birthday it's going to get an AIS input which should hopefully do away with the 'unidentified vessel about to run us down......'

Fair winds

Mico
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Old 01-27-2010, 11:49 PM   #4
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Although I agree with most of these thoughts, I feel a competent set of a drogue is most appropriate if the wind is blowing at 50+, at least on our boat. I have never started the engine, except when engaging both Hurricane Fredrick in Mobile in 1979, or during Jeanne in 2004 down in Florida. We have sailed and maintained bearing under bare poles during an unexpected squall or two in our days but usually they are not as bad as they sound like they are....but when heaving to alone is suspect, the drogue has always been the preferred selection for us.

The reality is, whatever makes you, AND your crew comfortable is the best course of action. Squalls happen..like it or not and your indirect preparation is key.....be prepared in advance by watching the radar...download your gribs.....overlay the chart and pay attention....if you are at anchor set a MOB (or whatever) to assist in determining your drift (if any) and be prepared to move at a moments notice. I believe, in the hands of a competetent skipper, being underway in most any blow, is the right decision.
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Old 01-28-2010, 06:29 AM   #5
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Quote:
Originally Posted by MMNETSEA View Post
Hello and Welcome to Cruiser Log,

Generally speaking squalls in the daylight hours give some time for the cruiser to prepare the boat for the passage of the squall (or storm) Understanding that gusts during the squall can easily achieve 60 knots and it is the sharp arrival of a gust during a sustained wind of say 35 knots that can do the most damage. First thing to do is to alert all on board to be on their planned stations. Present day sailing boats with their jib furling systems should be one of the first items to be thoroughly secured (unfurled = chaos!) then, all unsecured items in lockers or below decks. Main sail reefed right down. Engine started, boat turned into wind. Once all obvious preparations have been made - give the engine sufficient RPM to hold a steady position.

When the boat is moored or secured at anchor in an anchorage with other vessels then extra preparation is required - consider leaving the anchorage and head out to sea. Otherwise take a bearing on your position to ascertain if you are dragging. check the positions of other boats relative to your own and the approaching squall.

There is nothing like PREPARATION in good time.

Here are a few links in Cruiser Log.

Squalls

http://www.cruiserlog.com/forums/index.php...5&hl=storms

Read the special Navigation Notes in this one

http://www.cruiserlog.com/wiki/index.php?title=Portugal
Thanks for the welcome ... your solid advice ... and the links. Much appreciated!
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Old 01-28-2010, 06:42 AM   #6
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To all ...

How does one recognize ... and differentiate ... between: (1) frontal squalls, (2) microburasts/downdrafts, and (3) "white squalls?"

I've heard that the so-called "bulls-eye squall" occurs only off the coast of South Africa and in Nova Scotian waters. Truth or fallacy?

Lastly, what about an incipient waterspout while the funnel isn't readily visible? What about encountering a fully developed 'spout at night? Aren't they too small and transient to appear on radar?

Thanks.
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Old 01-28-2010, 08:44 AM   #7
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Shamrockery,

It might help if you tell us what you are doing and what sort of marine/sailing background you have? That might help us tailor the degree of basic detail we give you.

Quote:
Originally Posted by shamrockery View Post
How does one recognize ... and differentiate ... between: (1) frontal squalls, (2) microburasts/downdrafts, and (3) "white squalls?"

A frontal squall is part of a larger (frontal) weather system - essentially the leading edge of a cold front.

You can get microbursts and downdrafts in any squall. They are usually the result of vertical cloud development within the squall, but can also be due to shore effects.

There is some ambiguity about the meaning of 'white squall'. But usually it means a squall formed by sharp gradient winds and not the more normal cloud convection.


I've heard that the so-called "bulls-eye squall" occurs only off the coast of South Africa and in Nova Scotian waters. Truth or fallacy?

No. This is just a name use (in south africa) for a the normal small isolated squall common all over the world.



Lastly, what about an incipient waterspout while the funnel isn't readily visible? What about encountering a fully developed 'spout at night? Aren't they too small and transient to appear on radar?

You can see rain under the squall clouds clearly on radar, and you can usually see a formed ('fully developed') water spout - but "an incipient waterspout while the funnel isn't readily visible" would probably not be visible by definition
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Old 01-28-2010, 08:54 AM   #8
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Returning to the topic entitled " Squall Lines & Sea Breeze Fronts, S.E.Asia & Australian Waters"



We find some further information regarding Squalls in just one part of the world,. However similar conditions will be found in what are termed as the Inter Tropical Convergence Zones of the major oceans and seas. These zones lie some 8 degrees either side of the equator, but they are not stationary but move further North or South depending on many global climatic influences.

"Squall lines vary in length, some of the longest being those which develop in a pre-frontal trough 50 -100 nm ahead of a cold front. These squall lines may be several hundred nautical miles in length and 10 – 25 nm wide moving at typically 25 knots. The pre-frontal lines form ahead of the front as upper air flow develops waves ahead of the front; downward wave flow inhibiting and upward wave flow favouring, uplift. Squall lines are a common in northern Australia and north into Malaysia and Sumatra feature developing along active areas of the Inter Tropical Convergence Zone, within the feeder bands of tropical storms, along sea breeze fronts or other convergence zones and in the summer heat trough."

Squalls in colder latitudes are usually shorter in width and depth and with radar imagery give the skipper time to take avoidance action; But, they also may carry winds gusting 60 knots for short periods and therefore preparation for the event is equally required.

A drogue may be useful in certain circumstances - however generally speaking their use may actually hinder the ability to move the boat out of harms way.
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Old 01-29-2010, 01:56 AM   #9
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You can't predict microbursts at sea. Airports have sophisticated machinery to help predict the potential for one, and detect one, but only in the area under their control.

However, you can see strong downdrafts in developing storms. It will look like rain that falls only halfway from the cloud to the ground. What is happening is this:

As the could develops, it has primarily updrafts which keep the moisture particles aloft, banging into each other and becoming larger. Eventually, these combine into rain drops which become to heavy for the updraft to support and begin to fall, creating cooling currents within the cloud and thus, downdrafts.

Sometimes, a strong downdraft occurs before the particles are large enough to fall on their own. They get knocked out of the cloud, but evaporate on the way down. This is called Verga. It doesn't necessarily mean a microburst has occurred, but still a strong downdraft. A microburst is a VERY strong downdraft, which hits the surface and spreads out horizontally in a radial pattern with potentially 45+knot winds.

Pick up an Aviation Weather book. It's an excellent read and contains more information than you'll ever need for the 2-dimensional method of travel that is sailing.
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Old 01-29-2010, 04:33 AM   #10
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Quote:
Originally Posted by MMNETSEA View Post
Hello and Welcome to Cruiser Log,

Generally speaking squalls in the daylight hours give some time for the cruiser to prepare the boat for the passage of the squall (or storm) Understanding that gusts during the squall can easily achieve 60 knots and it is the sharp arrival of a gust during a sustained wind of say 35 knots that can do the most damage. First thing to do is to alert all on board to be on their planned stations. Present day sailing boats with their jib furling systems should be one of the first items to be thoroughly secured (unfurled = chaos!) then, all unsecured items in lockers or below decks. Main sail reefed right down. Engine started, boat turned into wind. Once all obvious preparations have been made - give the engine sufficient RPM to hold a steady position.

When the boat is moored or secured at anchor in an anchorage with other vessels then extra preparation is required - consider leaving the anchorage and head out to sea. Otherwise take a bearing on your position to ascertain if you are dragging. check the positions of other boats relative to your own and the approaching squall.

There is nothing like PREPARATION in good time.

Here are a few links in Cruiser Log.

Squalls

http://www.cruiserlog.com/forums/index.php...5&hl=storms

Read the special Navigation Notes in this one

http://www.cruiserlog.com/wiki/index.php?title=Portugal
MMNETSEA,

Thanks for the welcome plus your succinct tips and leads ... both very informative and helpful.

shamrockery

Quote:
Originally Posted by mico View Post
Totally agree with everything there Mmnetsea - another good tell tale is a drop in the barometer and the sudden apprehensive look on your good lady's face.

Seriously though, we found our radar absolutely fantastic in helping us dodge around squalls both in daylight and more particularly at night. Set at our full 25nm range with gain calibrated for rain and high definition we were able dodge around many squalls on the way to and back from Vanuatu and New Caledonia. Having never used the 'rain on' setting prior to our blue water and still wading through the instructions when we left Brisbane, we had mainly used it to alert us to other vessels. Discovering that it could also track squalls and fronts barrelling down on us was a significant comfort and more importantly, safety factor for blue water first timers such as us.

We have a Raymarine C80 radar and chartplotter. Next birthday it's going to get an AIS input which should hopefully do away with the 'unidentified vessel about to run us down......'

Fair winds

Mico
Mico,

Thanks for your pertinent advice and experiences, especially re radar. I'm compiling a fine consensus of do's and don't here.

shamrockery
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Old 01-29-2010, 04:37 AM   #11
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Originally Posted by Boomerang View Post
Although I agree with most of these thoughts, I feel a competent set of a drogue is most appropriate if the wind is blowing at 50+, at least on our boat. I have never started the engine, except when engaging both Hurricane Fredrick in Mobile in 1979, or during Jeanne in 2004 down in Florida. We have sailed and maintained bearing under bare poles during an unexpected squall or two in our days but usually they are not as bad as they sound like they are....but when heaving to alone is suspect, the drogue has always been the preferred selection for us.

The reality is, whatever makes you, AND your crew comfortable is the best course of action. Squalls happen..like it or not and your indirect preparation is key.....be prepared in advance by watching the radar...download your gribs.....overlay the chart and pay attention....if you are at anchor set a MOB (or whatever) to assist in determining your drift (if any) and be prepared to move at a moments notice. I believe, in the hands of a competetent skipper, being underway in most any blow, is the right decision.
Bommerang,

Thanks for your very helpful contributions to this discussion, e.g. drogues/sea anchors. First-hand experiences add a real sense of immediacy and reality.

shamrockery
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