Surface pressure maps (constant height maps)

• Surface pressure map - map of measured pressure at various stations (each at a different altitude) corrected to sea level.  All the measurements are to be taken at about the same time so that we can get a picture of the current weather.
•  Surface Pressure Map for Sept. 13, 1999 @ 5 A.M.  with isobars every 4 mb and labels every 8 mb.
• Regions of low pressure are called troughs.
• Regions of high pressure are called ridges.