Weather

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• Weather

Perhaps the most important single factor affecting boating safety and enjoyment is weather. Wind speed and direction, sea conditions, air and water temperatures and the presence or absence of sun, clouds, rain and fog all can have a tremendous impact on a boat outing. Here we discuss some important things to consider when boating on the Maine coast.

Monitor the U.S. Weather Bureau predictions and marine forecasts. Carry a weather radio so you can check forecasts throughout the day. Remember that local conditions can vary from the “zone” forecasts. A large island or bay can have its own weather system; take this into account when planning your travels.

Start your day early for calm conditions. The sun is the great wind generator and onshore breezes often pick up by late morning.

Wind

The key factor in a marine forecast is the predicted wind, since wind is weather as far as most boats are concerned. Because it is so important, let’s consider what the numbers mean:

• 10 mph or less: Pleasant breezes, fine boating. Small waves in open bays, but crests not breaking.
• 10 to 15 mph: Breezy, choppy in the open bays, with some whitecaps and streaks of foam. Rough for small boats.
• 15 to 20 mph: Rough in open bays for small boats under 20 feet. Frequent whitecaps and foam streaks.
• 20 to 25 mph: The limit of safe boating for most small boats.
• 25 to 30 mph: Seaworthy boat and skilled handling needed; dangerous for many small boats. Travel at your own risk.
• Over 30 mph: These are powerful winds: stay ashore.

The “small-craft advisory” issued by the U.S. Weather Service is a cautionary warning to boat owners that the day’s wind will be strong enough to make all open waters rough. It does not necessarily mean that all waters are unsafe for small boats, but that caution is needed and big waters should be avoided.

In summer, winds on the Maine coast are reasonably predictable as to strength, direction and duration. Easterlies and northerlies are normally mild in the summer (the exceptions being large storms off shore). These same winds are stronger and of longer duration in the fall, winter, and spring. Southeasterly winds can be counted on for light breezes and perhaps fog. A stationary high pressure area often will be accompanied by cool, gentle westerly winds.

If the forecast is for a hot day ashore, one can be pretty certain that a strong sea breeze will develop by early afternoon and will hold until the land cools down in the evening and the temperature differential evens out. During the day, the land may be heated many degrees higher than the surface waters (which remain in the upper 60s and low 70s). The warm air rises, cools as it moves seaward to replace the cool air below moving landward, and a coastal circulation is established. If the night remains warm, the sea breeze may continue well after dark before dying. When the sea surface is warm and the night on land is cool, the process may be reversed—with light breezes off the land for a few hours in the early morning.

Understanding these dynamics, small boaters may want to plan to head west or south in the morning and return in the afternoon with a following wind. While the “onshore sea breeze” may sound benign, it can kick up waves that make for rough going in small craft. If you want to avoid larger seas, get an early start and be off the water by early afternoon.

Fog

Foggy conditions can arise without warning and last for days, until a cold front passes through and the wind shifts northwest. Normally, winds accompanying fog are light, as strong winds tend to disperse it. A morning fog with a yellow sun overhead is apt to burn off. If the sky above is bluish over the fog, it will almost definitely clear. If you have been in a thick fog for several days, expect it to last until the weather system changes.

The most common type of fog is advection sea fog. This occurs when moist, warm air is cooled in its passage over cold seawater. Unfortunately, these conditions are most common in July and August–during peak boating season. Dense fog banks often form where the warm Gulf Stream meets the cold Labrador Current far off of Maine’s coast, and winds from the south or southeast can move this fog in toward shore.

Even if you never deliberately set out in a fog, it may envelop you while you’re on the water. When it reduces visibility, your other senses must take over. Listen for gongs, bells and whistle buoys to locate your position, but do not rely solely on these audible aids (as fog can distort the apparent direction of sounds). Listen for other clues signaling land nearby, such as the sound of surf breaking on the shore or the sounds of songbirds. If you are fogged in on an island and don’t have a compass, wait out the fog rather than risk heading out to sea.

Currents

You will encounter two principal types of current at sea: reversing tidal current and continuous ocean current. Strong current can aggravate conditions caused by adverse weather, particularly when current and wind are opposing. They can also cause difficult eddy and wave conditions even on still days from the sheer force of their flow.

Geography

Geography affects wind and water conditions in shallows, beach surf, headlands, cliffs and river mouths.

• Shallows: Waves steepen and break heavily on shallows. Avoid those areas when waves are large or when strong currents are forced to flow over them.
• Surf: Waves steepen and break on beaches and shoals. Generally, try to avoid landing in surf with a loaded kayak. Avoid surf on rocky beaches.
• Headlands: Conditions are frequently more difficult off headlands with chaotic seas due to increased wind (funneling), accelerated current and rebounding waves.
• Cliffs: Cliffs limit landing sites and can cause chaotic rebound wave conditions.
• River mouths: Difficult wave conditions occur when a river outflow runs against the waves.