FLOW FLOW...Refers to direction the wind is from in the upper atmosphere, i.e., the flow at 500 mb. Flow is usually prefixed by a number (such as 546, 564, 570, etc) which specifies the height (in dekameters) of the 500 mb surface. The height of the flow at 500 mb is useful because it indicates if the flow is warm or cold. Low heights (546) mean a colder flow. 590 would mean a very warm flow. Also, 564 often implies a greater likelihood of precipitation. Flow can also be prefixed with terms like cyclonic and W(est). Hence, "564 CYCLONIC W FLOW" implies a cool flow from the west that has cyclonic curvature to it, much like flow at the bottom (southern part) of a trough.