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The Different Types of Fog & How It Forms
November 5, 2022 at 04:33 AM EDT
By WeatherBug Meteorologist, Alyssa Robinette
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You may know fog as the low clouds that lower visibility and make you drive slower. But did you know that there are many different types of and ways that fog develop? Here are nine different types of fog.
Fog Over Water
- Commonly referred to as sea fog or lake fog
- Forms when warm, moist air flows over relatively colder waters
- Can occur over any body of water, but most commonly occurs along the U.S. Pacific coastline year-round given the water is typically much colder than the nearby land
- Can move onto land areas and result in hazards to motorists
- It forms when denser, cooler air on mountaintops sinks into valleys, and collects there. Over the course of the night, cooler and cooler air continues to fill in the valley, lowering the surrounding air temperatures closer to the dew point and subsequently saturation. If there is enough moisture in the air, fog will begin to form in these valleys as the night progresses.
- Commonly observed in the autumn and spring months
- Most dense around sunrise when surface temperatures are often lowest
- Forms when moist winds blow toward a mountain, causing the air to glide upwards and cool. The cooling of the air rising causes temperatures to meet up with the dew point, leading to saturation and forming fog on the top of mountains.
- Forms when a mixture of smoke and moisture released from damp smoldering organic material such as brush, leaves and trees, mixes with cooler, nearly saturated air
- Visibility is lowered to less than 10 feet
- Under light wind conditions, super fog meanders through low terrain areas such as creek beds or drainage ditches
- Can be very dangerous when present over highways, and has been the cause of several large, multi-vehicle pileups
- Forms when rain is fall through cold air – as rain start to fall through cold, dry air, it evaporates and causes the dew points to rise
- Most common with warm fronts but can occur with cold front if it is not moving too fast
- Tiny, supercooled liquid water droplets in fog can freeze instantly on exposed surfaces when temperatures are at or below freezing
- Most often occurs on tree branches, stairs and rails, sidewalks, roads and vehicles
- Can cause black ice to form on roadways, so extreme caution should be taken if travel is necessary
- When flying, a thin layer of ice can form on the aircraft, making the flight very dangerous unless the aircraft is treated or has effective de-icing equipment.
- Temperatures at 14 degrees Fahrenheit or below are too cold for the air to contain super-cooler water droplets, so it forms tiny ice crystals
- Only seen in the polar and arctic regions
- Forms as warmer, moist air moves over a cold ground
- May form under cloudy skies and with moderate to strong winds
- Initial stability of the atmosphere is relatively unimportant since low-level cooling makes the air stable near the ground
- Can last for several days and is most common un the U.S. on the West Coast
- Fog that occurs over water is most often advection fog
- Very common throughout the U.S.
- Most prevalent during the fall and winter
- Forms overnight as the air near the ground cools and stabilizes, and the fog will form once the cooling causes the air to reach saturation
- First forms at or near the surfaces, then thickens and extends upward as the air continues to cool
- The most favored areas for fog development are sheltered valleys where there is little to no wind as well as near bodies of water
- Wind disrupts the formation of radiation fog
- Is usually patchy, tends to stay in one place and goes away the next day under the sun’s rays
- Thicker instances of radiation fog tend to form in valleys or over calm bodies of water
Source:NWS
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Story Image by Ingo Jakubke from Pixabay
