A cold front is shown as a line with blue triangles. A dashed line shows a front that is still forming. The center of a low is where the warm and cold fronts meet. Radar sends energy that is bounced back, sensing anything that is larger then a raindrop, but can't see clouds. Yellow on a radar map denotes torrential rain.
Blue numbers refer to how high above the ground the rain is found.
Air moves to equalize the pressure difference. Air drifts from high to low pressure. Cumulonimbus clouds cause thunderstorms, some do not. Low moves counter-clockwise and inward while wind direction around a surface High moves clockwise and outward. Fronts When you look at a weather map you would notice that the air really spirals out of surface highs and into lows.