I would use "strong winds" in any situation where 1) The time range is enought that the wind will die down and then become strong again. 2) The area that I'm talking about is large enough that the strength of the wind will differ from one place to another. I would use "a strong wind" anywhere I'm talking about a relatively short time over a specific small area. (Weather report: "The Beijing area will be experiencing strong winds tomorrow" (large area over a full day). "That area of the ocean experences strong winds during the winter season." (Again, large area over an extended time) "The wind is pretty strong outside right now." (Small area - outside the hous, short period - right now)