I'd like to know the precise meaning of "flow" in the phrase "a flow of thunder" in the chapter five of The Great Gatsby by F. Scott Fitzgerald:
Outside the wind was loud and there was a faint flow of thunder along the Sound. All the lights were going on in West Egg now; the electric trains, men-carrying, were plunging home through the rain from New York. It was the hour of a profound human change and excitement was generating on the air.
The term "flow", taken from "a flow of thunder" in F. Scott Fitzgerald's The Great Gatsby, refers to the sound of the thunder moving in a continuous stream. Given that the line suggests that a storm is hitting, suggested by the loud wind and thunder, the phrase refers to the typical "rolling" of thunder.
This means that the thunder reverberates after it crashes. In stronger storms, one can hear thunder resonate over and over, in a wave-like fashion. Technically, "flow" refers to something (typically a liquid) which moves steadily and continuously. Think of the flow of a river, something constant and steady. In the same way, the thunder in this phrase is not singular like a strike of lightening. Instead, the sound of the thunder is continuous (as if it never stops).