AUS-M3000-Y-L2.4

Heavy weather command decisions

Yachts are built light, glazed generously, and fitted with shell doors, tender garages and beach clubs that a cargo ship would never accept. They are also, on a good day, faster than the weather. Both facts should shape your thinking, and only one of them is a comfort.

Entry & progression

The heavy weather decision that matters is made forty-eight hours out, in good visibility, with a cup of tea in your hand. Everything you do inside the storm is damage limitation on a decision you already made.

The options, in the order you should consider them

  1. Do not go. Stay alongside, or stay at anchor in a lee. It costs a day and no one thanks you for it. It is very often correct.
  2. Alter to avoid. Buy sea room early. A course alteration of thirty degrees, made two days out, is worth more than any amount of seamanship made two hours out.
  3. Run for shelter. Know the closest genuinely safe harbours on your route — genuinely safe in the forecast wind direction, not on the chart in general. Many yacht harbours become traps in a specific quadrant.
  4. Heave to / reduce and hold. Take the sea on a comfortable heading at the speed that lets you keep steerage and stop the slamming. You will lose ground. Accept it.
  5. Run before. Effective, and it invites pooping and broaching. Watch the following sea. Watch the surfing speed.

Tropical revolving storms

  • Give them room. The forecast track has a forecast error, and the error grows with time. Plot the danger area, not the track line.
  • The dangerous semicircle is the side where the storm's translation adds to its rotational wind and where you will be blown into the path. The navigable semicircle is the less bad one. Neither is good.
  • Do not attempt to cross ahead of the system. Ever. Not with a fast yacht. Not with a good forecast.

The motions that break things

  • Synchronous rolling — encounter period matches natural roll period. Change speed or heading; either will detune it.
  • Parametric rolling — a stern or bow quartering sea can pump a roll to alarming angles in a few cycles on a fine-formed hull. Change speed or heading immediately; it does not stabilise.
  • Slamming — reduce speed before the hull tells you to. Structural damage from repeated slamming is cumulative and expensive and often invisible.
  • Broaching — following seas, high speed, loss of directional control. The cure is speed, and less of it.

Preparing the vessel — the yacht-specific list

  • Beach club and garage doors: closed, dogged, and checked by a named person.
  • Tenders and toys: secured for a knockdown, not for a Mediterranean afternoon.
  • Free surface: press up or empty the slack tanks. Fuel, water, the pool, the jacuzzi.
  • Galley: hot food and drink cooked before it gets bad. A crew that has not eaten is a crew that will not perform.
  • Guests: briefed, seated low and central, sick bags distributed without embarrassment, and a crew member assigned to them by name.
  • Crew rest: rotate people out early. Fatigue arrives before the weather does.

WARNING — The owner will ask you to press on Sometimes politely, sometimes not, sometimes through the management company at 0200. It is the most predictable event in yachting. Decide, before the phone rings, what your answer is — and make the decision on the vessel's limits and the forecast, not on the conversation. Log the decision, the forecast you based it on, and the time you made it. Log the request, too. That entry has ended careers, and saved more.

Practice questions

5 questions
recallcore

recall · core

The most important heavy weather decision is made: (a) At the onset of gale force winds (b) When the first damage occurs (c) Around forty-eight hours out, when there is still sea room and time (d) When the routeing service issues a warning

recallcore

recall · core

Parametric rolling is best addressed by: (a) Maintaining course and speed until it damps out (b) Immediately changing speed or heading (c) Increasing speed to pass through the sea state (d) Filling the stabiliser tanks

recallcore

recall · core

In relation to a tropical revolving storm, a fast yacht should: (a) Cross ahead of the system while it has the speed to do so (b) Hold position in the navigable semicircle (c) Never attempt to cross ahead; plot the danger area rather than the track line (d) Follow the storm track astern of the system

recallcore

recall · core

Slack tanks in heavy weather are a problem because: (a) They increase the vessel's displacement (b) Free surface effect reduces the effective GM (c) They raise the metacentre (d) They increase the natural roll period beyond the encounter period

recallcore

recall · core

The owner telephones from ashore and asks the master to sail into a forecast gale to meet a charter start. The master should: (a) Sail, since the owner carries the commercial risk (b) Sail, and log the owner's instruction as the reason (c) Seek the management company's ruling (d) Decide on the vessel's limits and the forecast, and log the decision, the forecast, the time, and the request

AI-drafted catalogue content pending SME review. Sea service and course requirements change; verify with AMSA before relying on this for a career decision.

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