The National Weather Service issued a dense fog advisory this morning warning of fog with visibility levels down to one-quarter mile in some locations.
The advisory is in effect until 10 a.m.
It’s been a familiar refrain the past two weeks, with drivers being urged to use low beams and leave plenty of space between vehicles.
But why so foggy?
In South Florida, fog is usually an early morning hazard that can happen on clear nights with light winds.
Florida fog often forms when warm, moist air off the water comes into contact with the nighttime cooling surface of the Earth.
The temperature lowers to the dew point temperature, becomes fully saturated with water vapor, and fog occurs. The dew point is the temperature at which the air becomes 100 percent saturated.
Fog is basically a surface-level stratus cloud.
Among Florida cities, Tallahassee has the highest frequency of fog, while Key West has virtually no incidents of fog, according to the book “Florida Weather” by Morton D. Winsburg.
The National Weather Service sends out a special weather statement when visibility is reduced to one-half mile. If visibility dips to one-fourth mile, a fog advisory is issued.
Dense fog is rare in Florida. Between 2000 and 2011, NOAA’s storm events database recorded just 35 days during which dense fog was present statewide. But those incidences can be lethal.
The database lists five deaths and 17 injuries directly attributable to dense fog, while Palm Beach Post archives list multiple car accidents in which fog was involved.
In March 2007, Boynton Beach resident Anita Zoet died after her car plowed into an 18-wheeler on Florida’s Turnpike in heavy fog. Four others were also killed in the accident that included a 12-vehicle pileup.
A year earlier, two people were killed and 20 injured in western Palm Beach County when smoke combined with fog to reduce visibility on State Road 80 and U.S. 27.