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| CAN YOU SEE THE OVERPASS? |
Tule fog (pronounced /tu:li:/) is a thick ground fog that settles in the San Joaquin Valley and Sacramento Valley areas of California's Central Valley. Tule fog forms during the late fall and winter (California's rainy season) after the first significant rainfall, and is named after the Tule grass wetlands (Tulare's) of the Central Valley. The typical time frame for Tule fog to form is from November to March. Accidents caused by the Tule fog are the leading cause of weather-related casualties in California.
Tule fog is a radiation fog, which condenses when there is a high relative humidity (typically after a heavy rain), calm winds, and rapid cooling during the night. The longer nights during the winter months contribute considerably by rapidly cooling the ground thereby creating a temperature inversion (i.e. the air is colder at ground level than it is at 1000 feet altitude). That temperature inversion causes the moisture in the ground level air to condense and thus creates fog.
Visibility in Tule fog is usually less than an eighth of a mile (about 600 feet), but can be as little as a foot. Visibility can also, and usually does, vary rapidly. In only a few feet visibility can go from 10 feet to near zero.
This variability in visibility is the cause of many chain-reaction pile-ups on the roads and freeways. In December 1997, in one accident on Interstate 5 near Elk Grove south of Sacramento, 25 cars and 12 big-rig trucks collided inside a fog bank - five people died and 28 were injured. In February 2002, two people were killed in an 80-plus car pile-up on State Route 99 between Kingsburg and Selma (about 45 minutes northeast of Naval Air Station Lemoore) - visibility at the time of the accident was zero. On the morning of November 3, 2007, heavy Tule fog caused a massive pile-up that included 108 passenger vehicles and 18 big rig trucks on Northbound State Route 99 between Fowler and Fresno (45 minutes north of Naval Air Station Lemoore). Visibility was cut to about 200 feet at the time of the accident. There were two fatalities and 39 injuries in that crash.
Tule fog is a radiation fog, which condenses when there is a high relative humidity (typically after a heavy rain), calm winds, and rapid cooling during the night. The longer nights during the winter months contribute considerably by rapidly cooling the ground thereby creating a temperature inversion (i.e. the air is colder at ground level than it is at 1000 feet altitude). That temperature inversion causes the moisture in the ground level air to condense and thus creates fog.
Visibility in Tule fog is usually less than an eighth of a mile (about 600 feet), but can be as little as a foot. Visibility can also, and usually does, vary rapidly. In only a few feet visibility can go from 10 feet to near zero.
This variability in visibility is the cause of many chain-reaction pile-ups on the roads and freeways. In December 1997, in one accident on Interstate 5 near Elk Grove south of Sacramento, 25 cars and 12 big-rig trucks collided inside a fog bank - five people died and 28 were injured. In February 2002, two people were killed in an 80-plus car pile-up on State Route 99 between Kingsburg and Selma (about 45 minutes northeast of Naval Air Station Lemoore) - visibility at the time of the accident was zero. On the morning of November 3, 2007, heavy Tule fog caused a massive pile-up that included 108 passenger vehicles and 18 big rig trucks on Northbound State Route 99 between Fowler and Fresno (45 minutes north of Naval Air Station Lemoore). Visibility was cut to about 200 feet at the time of the accident. There were two fatalities and 39 injuries in that crash.
It may not LOOK like much. But, trust me. This is a GOOD day.
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| HOW ABOUT NOW? |
Those of us who have been here a few years know that it gets BAD. Last year, we had our Command's Christmas Party about 30 minutes away and you literally had to drive 15-20 mph WHILE looking at the white lines OUT YOUR DRIVER'S SIDE WINDOW. At the same time watching for taillights directly in front of you. Lessons learned.
This video was taken from an overpass I was standing on.
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