You are driving west in your car on a clear, warm day. up ahead, you see a dark band of ominous clouds. soon, you drive beneath the towering bank of clouds, and things get very dark. for twenty minutes, you are pelted with rain and even some hail. you keep driving west, even though it seems a little sketchy at times. on the radio, you hear that the next county to the north is under a tornado warning. then the sky lightens, and there is only a little rain. you notice that the temperature outside has dropped by 15°f (8°c). what have you just driven across?