What is this strange pattern down the east coast of America?

Washington Weather Chasers on Instagram: "It got crazy last night, especially around 4AM. The people describing the wind gusts as sounding like a jet or freight train were not exaggerating. In this clip you can hear the roar, see the sky lighting up with power flashes, and hear trees falling in our back yard and forest. Did you get strong wind gusts last night? Feel free to share what you saw in descriptive form, photo for or video form in the comments of this post. #wawx #weather #washington #w