Storm surge is the water rise, beyond the predicted tide level, that a storm generates. By contrast, a storm tide is the total water level rise during a storm, combining the tide and storm surge (see picture 1, below). According to the National Oceanic and Atmospheric Administration (NOAA), storm surge is often the greatest threat to life and property along the coast during a hurricane because it can cause extreme flooding particularly when it occurs during high tide. The combination of surge and waves can increase damage directly along the coast since surge allows waves to impact buildings further inland.
NOAA explains that storm surge is produced by the force of winds moving cyclonically around the storm and pushing water toward shore. Low pressure associated with intense storms has a minimal impact on surge compared to the impact of wind force (see picture 2, below). How much storm surge will occur at a specific location depends upon many factors such as storm forward speed, size, angle of approach to the coast, and central pressure; shape and characteristics of coastal features; and the width and slope of the continental shelf (shallow slopes are more likely to produce greater surge).
Picture 1: Storm Surge vs. Storm Tide