MARITIME PILOTING CHALLENGES -WIND AND WAVES

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Of all the challenges pilots face, wind is the most difficult to prepare for. In a few places winds are predictable at certain times of the year. Local sailors know how to control their vessels in these conditions. For the inexperienced or visiting pilot wind can be frustrating and sometimes dangerous.

Predicting Wind

Wind is the most difficult natural phenomenon to predict accurately. Storms and precipitation are easily tracked by ground stations or ship’s instruments. Tides and currents are known years in advance. Temperature changes and the condensation or fog that follows is usually known before it arrives.

Of course wind just doesn’t show up unannounced. Meteorologist can track the high and low pressure systems that drive winds. Specialized maps which show isobars and compression bands are widely available. General wind direction and speed predictions vary in accuracy from location to location.

How can Wind Effect Piloting?

Offshore

You don’t have to be a scientist to understand the effects of wind on a ship. Offshore areas have more predictable winds than coastal areas and the effects on operations are less significant. Correcting a course at sea is trivial; most wind concerns offshore have to do with wave action. Offshore buoys and weather stations do a good job of transmitting sea conditions in real time. The pilot can anticipate changes in sea state by keeping a close eye on the instruments. A good pilot considers wind direction and how a change in direction will impact fetch. Fetch is the distance a prevailing wind travels over open water before reaching shore or a vessel.

For example; if an off shore wind is blowing, the distance from the shore to the vessel is equal to the fetch of the wind. This is important because energy is transferred from the wind to the water surface by friction. The longer this friction takes place the larger the wave that forms. As larger waves form, friction increases and builds bigger waves.

Strong winds can also dictate what course should be steered. Even large ships must steer into the oncoming wind to avoid the side to side motion called wallowing. A wallowing ship is uncomfortable to be aboard, when it comes to passenger vessels always keep wallowing to a minimum. Sea sickness is mostly caused by the slow side to side rolling of a ship. Cargo can also break free or shift during heavy rolling.

Near shore

Winds near shore are a serious safety issue. Shallow waters can drive offshore swells into steep waves. Rocky shoreline or concrete face walls can reflect this wave action and cause multi-directional chop which can exceed the height of the original waves.

Wind also makes it difficult to maneuver in channels and harbors. Geography and structures may block some winds but funnel others to much higher speeds.

Large ships will have the help of tugboats when operating in these areas, and may choose not to enter a harbor until conditions have improved.

Smaller vessels do not have as many options in windy conditions. It is miserable to wait outside a harbor for hours while the vessel pitches and rolls. You will probably only get a cold meal as well since the cooks don’t want hot things slopping around the galley.

The most precarious situation is docking in winds that are blowing perpendicular to the face wall or dock. An offshore wind will cause quite a bit of frustration as you are blown back off the wall several times, causing you to attempt landing again and again. An onshore wind is worse, even a gentle and well planned landing arc might not keep the vessel from being slammed hard against the wall.

A powerful thruster package is no match for a strong wind. An incredible force develops when just a few dozen tons of vessel are pushed into a face wall at one or two miles per hour. Now multiply those numbers by ten and you will see what a challenge it is to overcome this situation.

When cargo ships had sails wind was essential to commerce but modern mariners have much less appreciation when the wind blows.