Dense, 450-mile-long fog bank lingering over central valley as experts blames unusual combination of weather factors
New Nasa satellite images reveal the scope of central California’s dreary December, caused by an enormous fog formation that has been haunting the Central Valley for weeks, trapping residents in colder-than-usual temperatures.
The low cloud formation, known as tule fog, first formed over central California in November and persisted into early December. The Central Valley typically sees this type of fog during the colder months of the year, when the air near the ground is cold and moist, and the winds are calmer, allowing moisture in the air to transform into a thick layer of fog.
As the cold blanket of fog forms, it becomes trapped in the bowl-like shape of the Central Valley. The warmer temperatures of the air above keep the fog stuck in the valley like a lid over a pot, also known as temperature inversion.
As seen in Nasa’s imagery, the tule fog remains steady over the Central Valley, moving through the Carquinez Strait in December, toward the San Francisco Bay.
