Noctilucent Cloud over Lake Merritt

At 6:00 AM on Friday morning, I padded to the front window wall to check out the day. The sun would not be up for at least another hour, but the dark time view of Lake Merritt is always so beautiful. I stood there looking out, slightly confused at what I was seeing. Despite the predawn darkness, there was a brightly lit, shimmery cloud hanging over the lake. It was magnificently lovely but rather mysterious. I took a quick cell phone snap and posted it online, tagging the National Weather Service.

NWS Responded right away, and next thing I knew…

"The rarest cloud in the world," declared the news headlines on the morning this unusually bright and shimmery cloud appeared over Northern California.

Noctilucent (“night shining”) clouds are created at super high altitudes when water droplets crystallize around dust particles. Visible only in the darkness of astronomical twilight, the frozen matter shimmers and sparkles with reflected sunlight that, for the observer, is well below the horizon.

Typically occurring near the polar regions, noctilucent clouds can sometimes appear in mid-latitude areas for unknown reasons. Studies have shown that early-morning space shuttle launches correlate to an increase in mid-latitude noctilucent clouds. The release of shuttle exhaust in the form of water vapor into the atmosphere, carried along by atmospheric tides, leads to the condensation of water crystals into noctilucent clouds.

There was indeed a Falcon 9 rocket launch that morning at Vandenberg Space Force Base, about 300 miles (482 km) away from my location in Oakland.

Although this noctilucent cloud appeared to hover right above Lake Merritt and the Oakland skyline, these clouds actually hang out about fifty miles high, at the top of the mesosphere. So anyone lucky enough to be looking out the window in Northern California that morning was treated to a rare and beautiful show.

This noctilucent cloud was truly an unforgettable sight, and I am thoroughly pleased to share this collective memory with other nephology enthusiasts. You can get a print of this amazing phenomenon right here.