Some weather terms are misunderstood or mistakenly interchanged. For professional truckers, this breakdown should clear up any confusion.
Fog vs. mist
Mist happens when tiny, microscopic water droplets hang around in the air. We see mist when warm, damp air is suddenly cooled. Fog looks similar but is thicker. The other difference between the two is how far drivers can see in them.
(Photo: Jim Allen/FreightWaves)
Generally, meteorologists report it as fog if visibility is below 3,300 feet — five-eighths of a mile or 1 kilometer. If drivers can see farther than that, it’s considered mist. Fog differs from a cloud only in that its base is at the ground. The term “mist” is also used in weather reports when there is such an obscurity and the corresponding relative humidity is 95% or more, but is generally lower than 100%.
Haze vs. smog
While mist and fog appear when water droplets are suspended in the air, haze happens when the particles are pollutants. Most of the time, haze occurs in areas far from the original source of the pollutants, which are carried by winds. Haze forms when light reflects off the airborne pollution particles and interferes with visibility. A naturally occurring source of haze includes smoke particles from fires, but more often than not the pollutants are man-made.
(Photo: Jim Allen/FreightWaves)
The term “smog” was first coined in the early 20th century in London, by physician Harold Des Veaux. He combined the words “smoke” and “fog” to describe low-hanging pollution over the city. But smog is really made up mostly of ozone. Pollutants like nitrogen oxides react with sunlight to form ozone, which makes some people cough and also can make their eyes burn. Stratospheric ozone high in the atmosphere is good, but ozone is dangerous when trapped in the lower atmosphere. It can cause chronic asthma and stunt agricultural productivity.
Tornado vs. waterspout
A tornado is a funnel cloud, or rotating column of air, that forms from the base of a thunderstorm and reaches the ground. A condensation funnel (the visible part of the funnel cloud) does not necessarily need to be all the way to the ground to be a tornado, but the circulation must reach the ground. This is often seen as debris, dirt, etc. swirling at the surface.
A waterspout is a column of rotating air that forms over water and makes contact with the water surface. A waterspout becomes a tornado once it reaches land.
Gust vs. squall
Wind doesn’t always travel at one speed. It becomes faster or slower. A gust is a sudden, short, strong blast of wind. Officially, it’s when the peak wind speed reaches at least 18 mph (16 knots), and the variation in wind speed between the peaks and lulls is at least 10 mph. The duration of a gust is usually less than 20 seconds.
(Photo: Jim Allen/FreightWaves)
A squall is a sudden blast of wind that lasts for more than a few minutes, especially one that is accompanied by precipitation. In the U.S., a squall is reported only if a wind speed of 18 mph or higher is sustained for at least two minutes.
Hurricane vs. typhoon
Mechanically, hurricanes and typhoons are the same thing — large, slow-moving cyclones with high winds and lots of rain. They are fueled by warm ocean waters in areas where wind shear is weak. They both can cause destructive floods, as well as widespread power outages and structural damage.
The difference is where they form. In the Atlantic basin — including the Gulf of Mexico and the Caribbean — as well as the eastern Pacific, the storm is called a hurricane. The word stems from several languages and was first used in the 1500s.
(Image: NASA)
If the cyclone develops over the western portion of the North Pacific, it’s called a typhoon. The exact origin of the name is unclear. But, according to the American Meteorological Society (AMS), it’s derived from either Cantonese, Arabic or Greek.
Click here for more FreightWaves articles by Nick Austin.
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