One quick and easymethod to estimate where the heavy weather will be found is to look at the500mb chart. On NOAA 500 MB charts issued by the Ocean Prediction Center(OPC), the 5640 m height contour is printed in bold. This is anexcellent marker for the southern limit of force 7-8 “westerlies” during thewinter season and force 6-7 “westerlies” during the season in thenorthern hemisphere.
http://oceanweatherservices.com/blog1/2013/02/26/using-the-500mb-chart-at-sea/