Geopotential Height - 500 mb -12 hr
This is a contour plot of 500 mb height in meters with a interval of 60 meters. The 500 mb level is often referred to as the steering level as most weather systems and precipitation follow the winds at this level. The winds follow the height contours and generally run from 30 to 100 knots. The speeds can be roughly estimated from the 300 mb winds as roughly 2/3rds their magnitude. This level averages around 18,000 feet above sea level and is roughly half-way up through the weather producing part of the atmosphere called the troposphere.