Atmospheric river's gusty breezes has Golden Gate Bridge singing

SAN FRANCISCO -- The howling gale forces winds, whipped up by Tuesday's Cat. 4 atmospheric river, whistled through the railing grates of the Golden Gate Bridge, creating an eerie sound track for the storm.

Winds were also whipping up as gusts over higher terrain have been peaking between 40 to 60 mph, triggering a wind advisory from the National Weather Service.  

"SFO airport has seen gusts between 35 to 47 mph thus far," weather service forecasters said. "Keep in mind that these windy conditions could also cause some downed branches/trees and make driving difficult"

The humming/whistling noise can be heard for miles and has been a source of annoyance for San Francisco residents ever since a handrail retrofit, designed to make the span more aerodynamic on gusty days, was put into place.

The slants are much narrower than the old handrails and vibrate in a strong wind.

"I couldn't really describe the sound," said Brianne Howell of San Francisco when she first heard the noise. "I think I described it as wind chimes at first and, then, like when you blow into a beer bottle. But then, like multiple beer bottles, because it's different tones."

Is it a hum? A ghostly wail? A Brian Eno-style soundtrack for the world's most beautiful bridge? The noise is not easy to describe. Howell had been chasing the source since April.

"What is that sound," she remembers asking herself walking through the Presidio. "I'm kind of like: am I the only one hearing this?"

Paolo Cosulich-Schwartz with the Golden Gate Bridge District has explained that the new railing makes the bridge more resilient to really high wind.

"The slats on the new hand rail are much thinner than the old hand rail which means that air can flow more freely across the bridge," Paolo Cosulich-Schwartz said.

The Golden Gate Bridge District says this was to be expected. During design, the district conducted wind tunnel tests on a scale model of the bridge under high winds.