Dangerous Quadrant

[perchance]

I keep hearing about the "dangerous quadrant" of a storm. What exactly is it and what makes it more dangerous than the other 3 quadrants. I am in the northern hemisphere if that makes a difference.

[44'cruisingcat]

Being in the Northern hemisphere does make a difference, since the cyclone will be revolving anti-clockwise - in the Southern hemisphere they revolve clockwise.

GENERALLY Northern hemisphere cyclones will move Northwest, Southern hemisphere Southwest.

The dangerous quadrant is in front of the cyclone where the wind rotation will pull you in toward the centre, so in the North that would GENERALLY be the quadrant from Northwest to Northeast.

I say GENERALLY, because cyclones have also been known to zig-zag and move in all sorts of directions.

[btrayfors]

Additionally, if the storm is moving toward you, it's speed is added to the wind speed (e.g., a 100 mph hurricane moving at 14 mph would have a total effective windspeed of 114 mph in the 'dangerous' quadrant).

Bill

[svHyLyte]

Storm winds circulate around a center of low pressure because of the law of the conservation of angular momentum. In the northern hemisphere, that is counter clockwise. At the same time, weather systems move across the surface of the earth for several reasons. In the northern hemisphere, tropical lows tend to develop near the northern edge of the intertropical convergance zone and then typically curve around and travel in a north-easterly direction at some speed. The wind one observes on the earths surface is the "apparent wind" of the storm which is the sum of the low's speed of advance plus the speed of the wind around the low. The dangerous quadrant is that part of the circle of the storm's rotation where the aparent wind is a relative maximum. The "navitable circle" is on the opposit side of the center of rotation. See Buys Ballot's law - Wikipedia, the free encyclopedia

[cal40john]

Also the fetch, time the wind spends creating waves, is longer on the dangerous side, so the waves are bigger.

John

[MarkJ]

I haven’t been in a cyclone and I don't know how good my weather info would be in one.. but say its good.... How hard would one push the boat to windward to get out of the Dangerous Quadrant and into the Navigatable Quadrant?
I’ve always thought to try very hard and then put out the para anchor, not just dump the anchor in front of the cyclone.
One would also imagine it would be a bit rough and might be foreced to deploy the para anchor becasue of the waves beginning to break when the boat is still in the Dangerous Quadrant

Mark

[cal40john]

Originally Posted by MarkJ

I haven’t been in a cyclone and I don't know how good my weather info would be in one.. but say its good.... How hard would one push the boat to windward to get out of the Dangerous Quadrant and into the Navigatable Quadrant?
I’ve always thought to try very hard and then put out the para anchor, not just dump the anchor in front of the cyclone.
One would also imagine it would be a bit rough and might be foreced to deploy the para anchor becasue of the waves beginning to break when the boat is still in the Dangerous Quadrant

Mark

If you're trying to sail to the Navigable semicircle, that would be downwind.

Law of Storms found in many references calls for running with the wind on the starboard quarter (northern hemi) if you are in the direct path of the storm, wind increasing in strength, unchanging wind direction, falling barometer.

If you're in the dangerous semicircle, wind conditions above, but wind veering, they call for heaving to on starboard tack, which is pointing towards sailing away from the storm center (and away from safe semi).

I've always thought that I might try to continue to sail close reaching on starboard if possible before heaving to, to get further out from the storm.

Closest I've come, I hove to for a day to allow Ignacio to get ahead of me as I was due north of it, and at least at that point the weather service was saying that my destination and its possible was Hawaii.

John

[GordMay]

Originally Posted by cal40john

If you're trying to sail to the Navigable semicircle, that would be downwind.

Law of Storms found in many references calls for running with the wind on the starboard quarter (northern hemi) if you are in the direct path of the storm, wind increasing in strength, unchanging wind direction, falling barometer.
If you're in the dangerous semicircle, wind conditions above, but wind veering, they call for heaving to on starboard tack, which is pointing towards sailing away from the storm center (and away from safe semi)...
John

Published in 1876, Piddington’s Horn-book is the classic text on the subject.

The Sailor's Horn-book for the Law of Storms (being a practical exposition of the theory of the law of storms) ~ by Henry Piddington

The Sailor's Horn-book for the Law ... - Google Book Search

[Marco]

I often think about the best way to approach an oncoming depression, as in few months i'll be sailing east to west from the UK to Newport in the US... truth is that i dont think there is much you can do on the average cruising boat. I have a Sigma 36 and considering a forecast for several days ahead is not that reliable, trying to run away from a depression might not be worth it, after all the depression might change its course and you end up positioning yourself right on its path. A solid boat should withstand a north atlantic depression and I think it's important thinking about what sails you'll use and how easy it is to get them up in anger... and when to take them all down and just wait.

Marco.
____________________________________________
Read my blog and preparations at www.jamorph.com

[GordMay]

See also:
The Practical Encyclopedia of Boating ~ by John Vigor
specifically, ‘Hurricane Tactics’ (page 159) for a clear & concise explanation.

The Practical Encyclopedia of ... - Google Book Search

[cal40john]

Originally Posted by Marco

I often think about the best way to approach an oncoming depression, as in few months i'll be sailing east to west from the UK to Newport in the US... truth is that i dont think there is much you can do on the average cruising boat. I have a Sigma 36 and considering a forecast for several days ahead is not that reliable, trying to run away from a depression might not be worth it, after all the depression might change its course and you end up positioning yourself right on its path. A solid boat should withstand a north atlantic depression and I think it's important thinking about what sails you'll use and how easy it is to get them up in anger... and when to take them all down and just wait.

Marco.
____________________________________________
Read my blog and preparations at www.jamorph.com

This hasn't been about outrunning storms or extended weather forecasts. It's been about trying to position yourself based on observed local conditions to try to reduce the effects of the storm. Sometimes it will do no good. Changing your position 50-100 miles relative to a 300 mile diameter hurricane could make a big difference in the conditions experienced. Positioning yourself relative to a 600 mile diameter extra tropical storm moving fast might make less difference.

John

[Marco]

Originally Posted by cal40john

This hasn't been about outrunning storms or extended weather forecasts. It's been about trying to position yourself based on observed local conditions to try to reduce the effects of the storm. Sometimes it will do no good. Changing your position 50-100 miles relative to a 300 mile diameter hurricane could make a big difference in the conditions experienced. Positioning yourself relative to a 600 mile diameter extra tropical storm moving fast might make less difference.

John

Hi John, sorry i might have misunderstood, but my point is really that on my boat I would sail so slow compared to how fast the centre of the depression or cyclone is moving that doing anything specific will only change the ordeal by little, i would concentrate on sea state and which way to ride it out with the boat in one piece. I think different boats respond differently to different sea states. I've never been in the situation, but i would not run with my boat, I would heave to beyond a certain point, or go bare poles with or without a sea anchor/drogue. My boat has pinched ends and is quite beamy, she tends to round up (and risk to be rolled) if i tried to run downwind... She is more manageable when at 70 deg to the wind than downwind, and this would give me more of a fighting chance... it would be totally different on an OPEN 60, there you'd run and run reducing sails or even under bare poles...

Marco
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