I was walking home along 4th Street, between the condos that are being built and the Allegro building (in Oakland), and I saw something strange in the sky pretty much due west of where I was, and somewhat low on the horizon. It looked a bit like a plane, but it was brighter, and seemed to be moving slowly. And rather than long thin contrails, it was leaving a short, wide vee in its wake-- almost an equilateral triangle. My perception is that it was over the bay, or near SFO.
While I stared, it looked sort of like it might have turned toward the east, and then a few seconds later it exploded-- there was a faint ripple of light in all directions, and then it was gone.
If I looked to the south, I could see a narrow, wavy contrail in the distance; I'm not sure if it was related.
I saw one of the missile defense launches from Vandenberg a few years ago-- it looked somewhat similar to this.
This sounds strange, I know.