Max Force Wind and Safety

[galleyslave]

Better stick to thinking in Beaufort rather than knots of wind. 35 knots with an ambient temperature of +5 degrees C is a very different animal from a summer blow with an ambient temperature of around 25 - 30 degrees C. The Beaufort scale tells you the effect the wind has and is a better guide.

[nigel1]

Originally Posted by GordMay

I also.

I think I have Force 8 to Force 12 pretty well to memory over the past 10 days, that was the weather in the northern part of the North Sea, but at least I was on a 16000 BHP tug, but with 30,000 tonne of rig hanging on the tow wire. Back in Aberdeen, and I guess after a night ashore I'll have forgotten all those numbers

[jkleins]

Originally Posted by galleyslave

Better stick to thinking in Beaufort rather than knots of wind. 35 knots with an ambient temperature of +5 degrees C is a very different animal from a summer blow with an ambient temperature of around 25 - 30 degrees C. The Beaufort scale tells you the effect the wind has and is a better guide.

But wouldn't scale be the same in both cases? Temperature is not part of the scale is it?

I never have been able to reconcile what you would call it if you had the wind but not the sea state or the sea state but not as much wind as the scale calls for. It seems to me to just be easier to state the wind and sea state instead of trying to infer it from a scale that may or may not describe what you are looking at.

This may just be my pet peeve though as I am convinced that medicine, law and a lot of other skill areas use terms to obfuscate rather then clarify.

Jim

[Solitude]

Wether its safe or not really depends on the crew. I never plan to go out in force 5 and above with the admiral onboard. With experience buddies its a different story.

[neilpride]

Originally Posted by SeaCow

Any context on that picture?

Well, this guy try lo leave the harbour in 60 knts plus wind in south east Queensland Australia to Yeppoon in central Quensland Australia and the weather forescast talk about 60 knts and 9 to 10 m waves , something really good wait for it in the next harbour??

[SeaCow]

OMG, thats just stupid. Waves of course have very dangerous dynamics near the shore.... If in it stay in, if out stay out! Dont cross that "border".

[SeaCow]

What was the outcome BTW? Quite an amazing pic but I would not want to have been on board that!

[Bash]

Originally Posted by jkleins

.
This may just be my pet peeve though as I am convinced that medicine, law and a lot of other skill areas use terms to obfuscate rather then clarify.

Jim, I don't think this is the case with the Beaufort scale. What the Beaufort scale is designed to do is provide an empirical system for determining and describing wind speed. It came from a time when the need was seen to standardize log entries. What one navigator called a gale another was calling a fresh breeze. Et cetera.

The system works remarkably well. For example, when you see frequent white horses, that's Force 4. When you start to see spray in the air as well, that's Force 5. Add foam on the crests and that's Force 6. When the foam begins to streak, that's Force 7.

This is not an esoteric system, at least not for a lot of us old timers, who use the scale to predict sail needs. It's a simple matter of changing to a #3 jib for Force 4, reefing as well for 5, double reefing for 6, switching to a #1 storm jib in 7, et cetera. Of course, such decisions vary from rig to rig.

Honestly, if you learn to use the system to determine Force 4 through 7, you've learned most of what most recreational boaters need to know. Let the big ships worry about differentiating between Force 11 and 12.

[SeaCow]

Beaufort was also created before there were tools to measure wind speed etc.

[galleyslave]

Originally Posted by jkleins

But wouldn't scale be the same in both cases? Temperature is not part of the scale is it?

The crucial point is sea state.

Beaufort describes the sea state resulting from the wind. Cold air is heavier and, therefore, contains more energy than warmer air moving at the same speed.

[galleyslave]

Originally Posted by nigel1

I think I have Force 8 to Force 12 pretty well to memory over the past 10 days, that was the weather in the northern part of the North Sea, but at least I was on a 16000 BHP tug, but with 30,000 tonne of rig hanging on the tow wire. Back in Aberdeen, and I guess after a night ashore I'll have forgotten all those numbers

I once got caught out in late October in a force nine NW in the Southern North Sea (Blackwater to the Orwell with a seven forecast). I was singlehanded in an engineless Folkboat. Several years later, I managed to persuade the Met Office to fax me the relevant reports, which they were, at first, unwilling to give me - something to do with not wanting to get caught up in any possible insurance claims.

For the record, I chickened out off Harwich - visibility in the flying spray was zilch, no echo sounder working, no GPS and the Cork Sand as a good soberer upper - and ran back to the Colne. I still had to beat in to Brightlingsea though, with 10 rolls in the main and a storm jib of about 3 square metres.

[Stillraining]

Originally Posted by galleyslave

Better stick to thinking in Beaufort rather than knots of wind. 35 knots with an ambient temperature of +5 degrees C is a very different animal from a summer blow with an ambient temperature of around 25 - 30 degrees C. The Beaufort scale tells you the effect the wind has and is a better guide.

This confuses me...Other then obviously wind chill... what does temperature have to do with the Beaufort scale and it interpolations on sea state?
Just asking out of ignorance here..

I use to know a lot of the windchill factors as a climber but those are long lost as well now...but they were memorized in MPH of wind not Beaufort.

I think it is how one learns something...for many metric It would seem comes natural ...for me its English units...to have in the minds eye what 50 knots sustained does to a sea seems easier then calling it force anything but I understand that it is a combination of both sea and wind state but its still tied into a wind parameter so I see no difference unless its possible to have say force 8 conditions with force 4 winds...if not its just and out dated nomenclature to me.

How many time have we argued over how big the waves actually were or were not in certain rescue situations around here..regardless of what the wind was doing...If a boue says they are 10' but with 55 knots of wind what force number is that really then if its a merriment of both conditions?

Second to Last point...When we listen to a sea story and a storm force factor being used to explain it at the time we always hear include the estimated wave height and the recorded wind speed and the sea's conditions seem to very from story to story in like conditions just as much as the system tried to clear up...so it seems of little use to me...sort of a shorthand at best over the radio to keep it simple and give an "Estimate of the conditions being encountered"

Last point..The scale can be thrown out altogether in inland waters as it has little bearing on sea state at all...I have been out in 47 knots with 3' wave in Puget Sound having the time of my life.

[galleyslave]

Sorry, I didn't express myself too well. I had just got up and was still in need of the first cup of coffee.

What is of concern in a sailing vessel is the amount of energy in the wind, some of which is, of course, captured to make the boat move. Wind energy has two components, mass which is dependent on temperature (the colder the air the greater the mass) and velocity. When you reduce sail, you reduce the volume of air, and by extension, the total amount of energy captured which is WHY you reef.

The point of using the Beaufort method for judging wind strength, i.e. energy per constant volume, is that it gives you a visual guide to it. If you know how your ship will react in a wind force as described by Beaufort, you have an instant guide as to what to expect. Wind velocity alone doesn't give you the whole picture. There are further complications arising from depth of water, currents, etc., which can only really be judged through experience but Beaufort gives you more information than mere wind speed.

[galleyslave]

What I should also have mentioned is that Force 9 was my interpretation of the conditions in my area, offshore wind, a relatively narrow channel between shore and outlying sandbanks and not too much sea running. According to the Met Office, the record for the area at the relevant time was Force 10. The forecast Force 7 was well within the capabilities of the boat but looking straight up the barrel of the gun with the wind funneling straight down Harwich Harbour and the Orwell river is the point at which I decided to turn back.

[Stillraining]

So what your saying is there is unwritten two beaufort scales... one cold air and one warm.

In flying we loose lift when its hot due to the less dense air but we have hard graphs as to its affects as with altitude as well..its not a guess.