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Old 17-08-2010, 15:28   #1
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Outrunning Storms

On a recent thread , the subject arose again of "Fin vs Full" and the issue of outrunning storms with a faster boat..
Im posting this tid-bit as its not just the boat but the opperator that need as much information concerning weather patterns and storms as possible while cruising..
I read this awhile back and it was so profound, I now keep a copy at the nave station in full fiew..
And Hear's the useable tip.
Using a weather chart or weather fax, down load the 500 milibar chart for the North Atlantic and the North pacific.. Look for the thick line designated "564" The school of "Masters, Mates and Pilots" teaches their students this rule of thumb for passage planning..
Stay 300 miles south of the 564 line for good crossing weather.. The reason for the 300 mile line is this, IF a preasure area pushes south, it gives the ship time to devert out of the way, For smaller and slower boats, you might want to stay 500 miles southwards..
The use of this line has become so inportant, its now more boldly printed than the other lines.
I believe this was taken from a copy of Ocean Navigator I recieved years ago........................
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Old 17-08-2010, 15:48   #2
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In reality, what they are advocating is to “avoid” areas of low pressure, not have the mindset to “outrun” them, which I think is foolish.

Using that outrun argument on Fin vs Full is simply a red herring
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Old 17-08-2010, 15:53   #3
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I think it was just a misuse of language, and was meant to convey the ability to get to a "softer" area of bad weather.

Randy - thanks for the tip!
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Old 17-08-2010, 16:20   #4
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Originally Posted by SaltyMonkey View Post
I think it was just a misuse of language, and was meant to convey the ability to get to a "softer" area of bad weather.

Randy - thanks for the tip!
The language was and is correct.... If I sence danger in any way, form or fashion, I'll alter my course and leave the area as soon as possible.. Hence, run from the storm........and not nesesarely a down wind run.. and the performance keel, being of fin design allows me to make progress on any point of sail in which I chose to travel, in a very fast motion...
The post also stated that slower and smaller boats should keep 500 miles south rather than 300.. Slower boat,ie-full keel cruiser, nuf said?
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Old 17-08-2010, 16:32   #5
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Originally Posted by Randyonr3 View Post
The language was and is correct....
Well, let the other blokes argue that part of the thread...(Pelagic)

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Originally Posted by Randyonr3 View Post
The post also stated that slower and smaller boats should keep 500 miles south rather than 300.. Slower boat,ie-full keel cruiser, nuf said?
For a slower boat thats roughly 5 days of sailing @ 100 MPD...not sure that's possible given forecasts of 48 hrs is about all you can go on.
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Old 17-08-2010, 17:49   #6
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Slower isn't full keel. Boats tghag will surf can do some pretty impressive daily runs in the right direction. Guess what, a full keel boat will also, though not quite as good as a ULDB. The question is what direction the wind and waves are coming from and the direction you want to go. Any old POS can make decent times on a reach if the waterline is long enough.

We really aren't talking of outrunning a storm as they typically move at 15k or more. You are really trying to get out of the way heading off at a right angle in the direction of least danger. Given 48 hours notice, even a slow boat can stay out of the really nasty areas of a Hurricane. Large lows as regularly hit the NE and NW are a little more problematical because of their size.

I've got one of those slow and old full keel lead mines. Damned if the POS didn't average nearly 150nm per day, on a just completed single handed Transpac. That was in moderate conditions with winds of 10-15, most of it from dead astern. That's not it's most advantageous point of sail.

Talk of buying a boat to outrun storms is really only for the hotrod sailors in large fully creweds ULDB's and multihulls. The rest of us cruisers will just get out of the way.
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Old 17-08-2010, 18:00   #7
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Oh, you had to say the multihull thing...now I am drooling
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Old 17-08-2010, 18:02   #8
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Unless you are sailng on an Open 60, you ain't gonna outrun a storm. At best, you are just going to delay getting slammed by a few hours.
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Old 18-08-2010, 06:51   #9
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500 mb chart analysis is a great tool for predicting gales and storms in the mid- and higher latitudes, but doesn't really help in the tropics. When a tropical storm approaches, the Tradewinds almost always die out. If you plan to run, you're left relying on your engine(s).
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Old 18-08-2010, 08:00   #10
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Big problems can develop when a 500 mb trough over runs a surface low. When they meet up the barometer will fall through the cellar and you can figure a pasting is in the offing.

Gribs that show multiple days of 500 mb and surface lows are good info to have.

Don't be where they meet if you can help it.
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Old 18-08-2010, 08:05   #11
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Quote:
Originally Posted by Randyonr3 View Post
The language was and is correct.... If I sence danger in any way, form or fashion, I'll alter my course and leave the area as soon as possible.. Hence, run from the storm........and not nesesarely a down wind run.. and the performance keel, being of fin design allows me to make progress on any point of sail in which I chose to travel, in a very fast motion...
The post also stated that slower and smaller boats should keep 500 miles south rather than 300.. Slower boat,ie-full keel cruiser, nuf said?
Could be that faster boats are POWER BOATS and slower boats are sailboats, all sailboats...Whatever makes you feel like you have the superior vessel is OK with me..

Just be careful your keel doesn't fall off! haha I actually heard that happens once in awhile. Something about having the keel attached by bolts that are stressed whenever the keel hits something. This being compounded by the fact that the bolts sit in salt water. Imagine!! I can't..
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Old 18-08-2010, 08:38   #12
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Good point. Forgot about tropical lifts, dies, and inaccuracy of GRIBS.

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500 mb chart analysis is a great tool for predicting gales and storms in the mid- and higher latitudes, but doesn't really help in the tropics. When a tropical storm approaches, the Tradewinds almost always die out. If you plan to run, you're left relying on your engine(s).
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Old 18-08-2010, 10:17   #13
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The use of this line has become so inportant, its now more boldly printed than the other lines.
On the 500mB chart, the contour lines indicate altitude of 500mB pressure; 564 is 5640 metres ASL, which equates to atmospheric standard conditions. Higher numbers indicate warm air aloft associated with ridges and lower numbers with cold air aloft associated with troughs. So generally speaking in the N hemisphere you could use 300 miles south of the 564 line as being safe, but you can't depend on that always being the case.
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Old 18-08-2010, 10:34   #14
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Stay 300 miles south of the 564 line for good crossing weather..
Just for giggles I pulled (and attached) the current 500mb (the black lines, and the bold dark line is for 564) and the surface winds (the arrows) for the N atlantic.

I honestly don't think this rule adds much value. Its a pretty blunt instrument. It would normally prevent you from getting to England and it does not seem like it would prevent you from getting slammed by the gales that cruise off the east coast and then along 40-50N (there just happens be such a low, not quite a gale but . . . in todays picture), and Huds right it is of no use for the tropics.
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Old 18-08-2010, 10:44   #15
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Randyonr3, it is a good tip and sorry for focusing on the semantics of out running storms as a basis of choosing a keel design. (pet peeve)

When working commercially in the PNW… I used the 500mb level charts constantly ….especially in the wintertime (Gulf of Alaska) to help predict how “Families of Lows” would interact and be steered by upper level conditions.
Very useful tool.
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