In either the track header or in each individual audio clip, you'll see a little rectangle with two knobs sticking out either side. Click on this to bring up the Effects plugin screen. Probably the simplest effect for your purposes is Graphic EQ. Double-click on this effect and then click OK. You'll now see a quite normal looking panel with 10 sliders for different frequency ranges. Adjust these as necessary; you can even adjust them while the video is playing so you can hear the result in real time. Most of the wind rumble is probably in the 28, 56, and 113Hz ranges, and most of the whistle is above 3.6k. Fortunately, voices tend to fall pretty much in the middle so removing the outer frequencies won't affect them much.