Blind Faith Page 2

<br Without question, fog is the biggest reason sailors cite for avoiding the Maine coast in summer, despite the fact that it is otherwise an excellent cruising ground. Although sailing in Maine can indeed be quite opaque, this need not be too disconcerting. Instead of being mindlessly fog-phobic, it is better to view fog, wherever you meet it, as just another navigational puzzle to be
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WHAT KIND OF FOG?

Meteorologists recognize four distinct types of fog. Knowing what type is present can help you cope with it more effectively.

Advection fog

Also known as sea fog, this is the most common type. It’s formed when warm, moist air passes over cold water. The cold causes the moisture to condense, forming tiny water droplets suspended in the air. Sea fog appears most often during the summer, especially at night and during the morning. It is thickest when the wind is light and tends to thin as the sun shines brighter and winds pick up in the afternoon.

Radiation fog

Also called ground fog, this usually forms at night and in the early morning when the air is still and the sky clear. In these conditions, air near the surface cools more rapidly than the air aloft. If the air is cooled enough, the moisture it contains will condense and form fog. Radiation fog doesn’t usually last long. The warmth of the rising sun and/or a breeze of more than 5 knots usually disperses it by mid-morning.

Precipitation fog

Also known as “rain fog,” this occurs when rain from warm upper air layers descends through colder air near the water’s surface. Water vapor from the descending raindrops condenses and forms fog. It can occur most any time of the year with winds southwest through east. When the rain stops, the fog usually lifts, especially if the wind keeps blowing.

Steam fog

Commonly called sea smoke, this is caused by very cold air passing over markedly warmer waters. It generally occurs in winter, but can form in the late summer and the autumn. It behaves much like steam rising from a hot bathtub, obscuring visibility at or near the surface of the water. Increasing wind tends to dissipate it, as does the warmth of the midday sun.

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