Isotach

An Isotach map is one that displays lines of equal wind speed.  This isotach shows the wind speeds in the Southeast U.S. and the Gulf of Mexico. AN isotach also displays the direction from which the wind is moving.  This image shows converging winds in the center because an area of low pressure is forming.   http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1456&tstamp=&page=5