Hurricane avoidance

[Ross]

Given that the winds are counter clockwise

Sailing south in these conditions would put the wind on your back and gradually coming around to your starboard quarter. The factor that was not noted is that the swells generated by such a storm would provide several days advanced warning of the approach of this storm. In the northern hemisphere tropical storms generally move west to north west so sailing south at right angles to the path of the storm or tangent to the swells will take you out of the worst of the storm. Running before a storm simply keeps you in the storm longer.

 

[Clyde]

What Hurricane Avoidance? *o

An average hurricane is 300 to 400 miles WIDE! The hurricane winds (74 to +155 mph) can be found 25 to 150 miles from the center of the eye of the hurricane. Gale force winds (39 to 73 mph) will be found 300 to 400 miles from the eye of the hurricane. Hurricane Carla had hurricane force winds of 300 miles from the eye and gale force winds 500 miles from the eye!Plotting your position and heading against the track of the hurricane you can graphically get the "Closest Point of Approach". The hurricane was bearing 120 miles at 100 degrees true from the vessel. The heading of the hurricane was 275 degrees true at a speed of 25 knots. The vessel was heading 50 degrees true at a speed of 13 knots. Converting knots to mph (for consistency of units):13 knots = 15 mph25 knots = 29 mphPlotting the movement of the hurricane at 20-mile increment and calculating the time it took, you can then plot the distance the vessel will travel against the hurricane. Hurricane traveling at 29 mph at a heading of 275 degrees true.Initial bearing 120 miles at a bearing of 100 degrees true from vessel.(20m, 0.69hr, 275 degrees true)(40m, 1.379hr, 275 degrees true)(60m, 2.069hrs, 275 degrees true)(80m, 2.759hrs, 275 degrees true)(100m, 3.448hrs, degrees true)Vessel traveling at 15 mph at a heading of 50 degrees true.(0.69 hr, 10.34m, 50 degrees true)(1.379hr, 20.69m, 50 degrees true)(2.069hrs, 31.03m, 50 degrees true)(2.759hrs, 41.38m, 50 degrees true)(3.448hrs, 51.72m, 50 degrees true)Using a scale to measure the distance between the hurricane and the vessel from the plotted positions of the hurricane and vessel:95 miles73 miles54 miles46 miles53 milesThe CPA is about 46 miles at 2 hours 46 minutes. You could plot more points to get more accuracy and take your time in measuring; I just plotted it quickly and got a quick measurement value. You could increase the CPA by sailing 90 degrees to the hurricane which would be a heading of 5 degrees true, but it would be useless at 120 miles you are basically already in the hurricane. There is no way that you can sail south or southeast across the track of the hurricane 120 miles from your position moving at 25 knots while having a vessel speed of only 13 knots to avoid it. In this scenario it doesn't matter what direction you sail; there is no avoiding the hurricane because you are already in it!Fair Winds,Clyde

 

[r.w.landau]

Clyde, Key words: " If you maneuver

at 13 knots to avoid the hurricane"That means you change course to avoid it..."what could be your CPA?"That was the original question.Clyde, those were my first calculations until I realized, thanks to wjssr that I was headed right into the worst/ danger quadrant of the hurricane.The point is heading 90 degrees to the right quadrant of the hurricane that would be 185 degrees.At the original coordinates, you were less than 10 miles north of the hurricane path. The point is it would be better to be hit by the lesser quadrant than the dangerous quadrant.So that hour loss set you back 13 nautical miles moving south over the hurricane path but it put you 60 nautical miles into the safer side of the hurricane.r.w.landau

 

[Franklin]

But....

If it was a new Hurricane (I would sure hope people wouldn't be out with an old one) then it could just be barely a Cat 1 at 75 mph in the heart of it...give it another 25 miles of that and it starts to scale off. Usually though, it takes a day or more for it to develop into a hurricane from a tropical wave and when you get in that tropical wave you should be trying to figure out what is going on and getting out of there.18 months ago I asked the question: "What do you do if a hurricane forms near you" and I got blasted for it. I guess I gave the impression that I was going hunting for one. In any case, I searched and searched for info and found the answer. The best answer I found was by doing a search on google books for something like storm tactics (it's in the archives). The author was an old salt from the 1890s who, by trade, happen to experience hurricanes first hand because they didn't have all that fancy weather equipment back then. The guy explained how to tell the difference between a gale and a tropical storm. He explained how to determine the course of the storm without fancy equipment or communication. He explained the course of action on how to avoid the storm. That is what I based my post #11 on.I would also have to say that in this case, it would most certainly be a small hurricane if one is just realizing it 120 miles away. As somebody already posted, the swells give it away before the wind does...but sometimes only a day ahead (depends how strong and how old the storm is...I know because I love surfing the storm waves ). But still, one can get pretty far out of the path with 24 hour notice and good winds and that's what kept those old salts alive back then. Sometimes we get spoiled with our GPSs, autopilots, fantasic charts and cruising guides. Almost takes all the fun out of cruising Why is all this important? Because sometimes mother nature doesn't do what it's supposed to do. Take that tall ship that got caught up in a very strong hurricane because it took the south path because hurricanes aren't supposed to go south...but did that time and sunk the poor old salts. Also take note of the preseason and postseason storms we've had in the altantic and pacific the past few years.

 

[Ross]

Clyde, Most of the time tropical systems

in the northern hemisphere move west to north-west to north. After they make landfall all bets are off in terms of where they go next. This is all a game of "You bet your life". You must study the nature of the winds around a storm. If you were looking at the storm system from space and the circular rotation was a clock face the direction of travel is toward 12 o'clock the strongest winds are from 4 o'clock to 12 o'clock, because the winds of rotation and the direction of travel of the system reinforce each other. The winds diminish as you approach the 9o'clock position in the storm because the forward travel of the storm subtracts from the velocity of the rotational winds. Therfore it is going to be safer on the morning side of the storm. Make no mistake it is still a storm and it is still dangerous. Remember that 84 mile per hour winds blow twice as hard as 60 mile per hour winds. So every little bit helps.

 

[Bill Roosa]

Bowditch notwithstanding

Assuming the intent is to get as far away from the center of the storm as possible and be on the south (in this case) side of the storm and we are in the northern hemisphere. I'd run with the wind over my starboard quarter on a heading of 225T. As the wind came around in about 5 hours I'd turn to the east to keep the wind over my starboard quarter. Doing this gives me a CPA of 90 nm at around 6.5 hours.By running south and with the storm I increase the amount of time I can head south. If I run south and into the storm (<185T) I would shorten up the distance between the myself and the center more quickly and don't get as far away from the center. If I just head at 90 degrees to the storm course I end up somewhere in between.With that said, If Mr. Bowditch says "if you are in this sector of the storm, keep the wind over the starboard bow" that is what I'd do. Beating vs running.

 

[Clay]

What Ocean Are we talking

The poster said hurricane, so I'm thinking the Atlantic, but heading towards 275T, if ever ?

 

[r.w.landau]

Clyde, 275 is just 5 degrees north of due west.

275T is the direction the hurricane is headed.r.w.landau

 

[Ross]

Clay , 275 is almost due west.. Is there a problem

with tropical storms moving west? Since they form in the mid atlantic they must travel west to reach the good ole US of A.

 

[Clay]

Don't know what I was thinking

I was looking at the compass rose on my chart, playing along trying to understand. I honestly do not have a great understanding of plotting that's why I engaged.As for my 275T comment, now sounds foolish even to me. While looking at the rose, I Looked down thinking south right away, must have been late, sorry.

 

[Benny]

OK, Bill what is your answer for the exercise?

I agree that heading SSW will provide additional time to put you farther away from the center of the storm.

 

[Clyde]

Sailing in a Hurricane! *yks

I looked at the speed plot of the hurricane tack of 275 degrees true at 29 mph against the vessel on a heading of 225 degree true at 15 mph and it came out to be 4 hours 50 minutes with a CPA of 51 miles. I've never sailed in a hurricane. That said, the hurricane survival guide states that if you get caught at sea during a hurricane, you NEVER CROSS THE "T"!! Or in other words you never sail cross the track of a hurricane. If you get caught right of the hurricane track, you'll have to beat to weather, if you get caught left of the track you'll have to run. The winds rotating around the hurricane are at different speeds and direction. You have to sail relative to the rotating wind speed and direction. There is no way you can maintain a heading and expect the wind to maintain its speed and direction in a hurricane.If you're on the right you'll have to beat to weather with the wind 45 degrees relative to your bow on the starboard side. If you are dead-a-head of the track, you'll have to run with the wind at 160 degrees relative to your bow at the starboard quarter until you are pushed around into the left front quarter of the hurricane. If you are in the left you'll have to run with the wind at 135 degrees relative to your bow at the starboard quarter until the hurricane spits you out. If you're behind the hurricane just sail whatever course you can to get away from the hurricane.Fair Winds,Clyde