The city by the Bay


The worst shipwreck in San Francisco history occurred off Land’s End in February, 1901. The Rio de Janeiro, a steam-powered passenger ship, sailed photo-1 5through the Golden Gate Straits in heavy fog. With very little warning or time to react, the iron-hulled ship hit a shallow reef near Fort Point and began to sink. The fog dulled cries for help and hampered rescue boats. Within 8 minutes the ship was gone and only 82 persons had boarded lifeboats. 123 passengers and crew, including Capt. Ward, drowned in that wreck.

San Francisco fog is poetic, evocative and hazardous when coupled with our shallow Bay and rocky coast.   In a heavy fog in November, 2007 the Cosco Buson container ship struck the Bay Bridge, spilling 53,569 gallons of fuel into the Bay. In a fog of January, 2013 the Overseas Reymar, a large tanker, scraped its hull against the Bay Bridge, raising questions about its navigation equipment. Records of airplane crashes, car wrecks and ferry collisions expand the litany of fog-related disasters.

The persistence of Bay area fog arises from our unique geography, climate, and wind. Northwest ocean currents and “upwelling” along the coast result in cold coastal waters (52-58 degrees F). Over the ocean moisture evaporates, creating a “marine layer”, which, cooling, condenses into fog. The extreme variance of temperature between the hot inland valley and the cool coast suggests a high pressure zone and a low pressure zone. Wind blows towards the low pressure zone, along the coastline and through the narrow gap of the Golden Gate Straits. As the wind blows, the fog accompanies it, blanketing the coastal mountains, the Bay, and San Francisco.

Regular recurrent fog determines Bay area ecology. Redwood trees, sword ferns, huckleberries, and tan oaks depend on the fog for moisture. Napa and Sonoma Valley grapes reach perfection with the help of the fog. Local salamanders and frogs would die of heat stroke were it not for the cooling fog. In the midst of summer, San Francisco is cool.

To take credit for all the benefits of a foggy day, @KarlTheFog steps forward. As his Twitter feed announces, “All that is sunny does not glitter, not all those in the fog are lost.”  Join Karl’s 55,000 followers on your Twitter Feed.