San Francisco Chronicle - (Sunday)
Dank invader from delta — tule fog
Maybe you noticed: In the middle days of November, tule fog has come creeping into the bay on little cat feet. Tule fog is also called valley fog or ground fog. It is a much different breed of cat from the familiar ocean fog of summer that rolls in from the Pacific.
The summer fog rises when warm inland air draws cool wet air in from the ocean, and the fog moves in from June to September, rolling over the hills in waves, like a gray ocean, roaring through the Golden Gate on the back of the westerly wind.
The wintry fog rises inland and creeps, rather than rolls, from the valley to the ocean. It begins on quiet, almost windless nights in the Great Central Valley, often just after a rain, when the air cools and the mist rises in tiny droplets. It moves on the easterly winds of fall and winter. Or it doesn’t move at all — it can be dark, gray, impenetrable. Tule fog can be dangerous: Sometimes the visibility on the highways drops to zero.
The fog formed on several days last week and extended from the south end of the Sacramento Valley all the way down the San Joaquin Valley. Sacramento and Bakersfield were both socked in. The valley fog made its way through the Carquinez Strait and into San Francisco Bay. Napa, Marin and Contra Costa felt the gray chill. On a couple of days, the tule fog covered parts of San Francisco closest to the bay. It felt odd: Instead of the fog rolling in the Golden Gate, it moved out, toward the ocean.
Only a weak weather front at week’s end drove it away. But the fog will be back when the rains come again.
The ground fog gets its name from the tall green reeds called tule (pronounced TOO-lee) that grow in the SacramentoSan Joaquin River Delta and on marshy shorelines. The native people wove tules to make baskets and even boats. The most famous native boatman on the bay was a Miwok man the Spanish called Marino or Chief Marin. The county is named for him.
If you think there have been fewer bouts of thick tule fog in recent years, you are right. Tule fog forms after rain and damp weather, and California has been in a drought for years now. Dry and warm weather — and the fire season — extended into October, November and even into early December. This cut the tule fog season significantly.
Fog is one of those natural events that makes legends and stories, and tule fog is no different because of its dark and wintry nature. I myself recall thick winter fogs, especially in my misbegotten youth when I worked near the waterfront. I remembered days when I could barely see to drive home. So I asked around: Was there more tule fog a few years ago, or was it my imagination? Mike Pechner, a local meteorologist, told me he remembers growing up in Novato, just a bit inland from San Pablo Bay, when there would be “weeks and weeks of ground fog. And no sun at all in November.”
Rich Reed, a seaman who operated pilot boats on the bay approaches and the delta, remembered days on the rivers when the ground fog was so thick and so low to the water he could see cows grazing on the river levees 10 or 15 feet high. “We could see everything but the water,” he said in a Facebook post about the fog.
One of the dangers of tule fog is that it often hangs low to the ground, like a thick gray curtain. The fogbanks sometimes form in little hollows or ravines, and the visibility drops to nothing.
There have been some spectacular traffic crashes — the biggest in November of 2007 on Highway 99 near Selma in Fresno County when 108 cars and 18 big rigs crashed in the fog. Two people were killed and 39 hurt. I covered a couple of these crashes myself in my reporting days: one on the Yolo Causeway between Sacramento and Davis, another on Interstate 5 on the west side of the San Joaquin Valley. I don’t remember the details, but I recall what the witnesses said: They were driving at what they felt was a safe speed in grayish daylight weather when suddenly they could see nothing. Cars slammed into each other in nightmarish chains of crashes.
You know what they say in the news business: There are two sides to every story. The tule fog can be beautiful, too, if you are careful around it.
A couple of years ago, I was staying in Sausalito temporarily and working in the city. On some days, if I was lucky, I’d catch the morning ferry. I even had a favorite seat, on the upper deck, out of the wind. One November morning, the fog started not five minutes after we left the Sausalito dock. It closed in; everything was gray.
We sailed on: a tule fog for sure, thick and chilly, 20 minutes and more without a sight of anything. The skipper had sailed this route a thousand times, knew the currents and tides, and was navigating with the aid of radar, but he blew the whistle regularly; you never know. The bay is full of traffic: big ships, but also small boats, maybe even kayaks. They needed to hear the ferry coming. Sometimes, on my seat on the upper deck, I could hear whistles of other vessels: a ferry coming down from Vallejo, maybe a tug, something else.
I could see nothing, but sometimes there were other sounds, foghorns, bells on buoys, echoes. Maybe we were abeam of Alcatraz. I couldn’t tell.
Then, just about 25 minutes after we left Sausalito, we came out of the fog into broad sunlight and there was the San Francisco Ferry Building with the glass towers of the city behind it in bright autumn sunshine. It was like going to the opera and watching the stage curtain going up on a city on a stage set. Wow, I thought, an urban adventure for the price of a ferry ticket.