GOES image: parallel trains of clouds. What to make of them? Here is a GOES visible image from today, 2019-12-01 about local noon, around Nova Scotia. Note the parallel trains or streaks of clouds, running approximately northwest to southeast.  

A few hours ago, the wind was from the NW at 30-40kph (at Halifax); for the past 3 hours it's been from the NNW at about 25kph.

What's the physics behind the streaking? Is it simply cumulus clouds from convection being blown downwind?
The species is Stratocumuls undulatus Sc un.

They can form for example when cold, dry air moves over a warmer ground layer. A sharp wind shear at the boundary layer blows these waves. (Wikipedia on Sc).

They are not to be confused with Sc radiatus or yet another form, the so-called "cloud streets", which form along the wind direction.