🔍 Key Concepts

• Storm surge mechanics on enclosed waters like the Great Lakes (wind setup and barometric pressure effects) • Relationship between wind direction and the long axis of a lake and how that affects water piling up at one end • Difference between a storm surge and a seiche (standing wave after the forcing stops)

💭 Think About

• Think about how wind blowing steadily over a long distance of water (long fetch) will move water: along the length of the lake or across its width? Which gives the largest level difference between ends? • Ask yourself: does a seiche usually develop when the forcing (wind) stops suddenly or when it dies out very slowly? How would that affect the water’s ability to oscillate back and forth? • Consider whether a storm surge on a long, narrow lake would change the level at only one end, or if raising it at one end implies a change somewhere else in the basin.

✅ Before You Answer

• Verify that storm surge is primarily caused by strong, persistent winds, with barometric pressure changes as an additional factor on water level. • Check whether a seiche is defined as a free oscillation that often occurs after a rapid change in wind or pressure, not during a slowly changing condition. • Confirm that when water is piled up at one end of a long lake, the water level at the opposite end must change in the opposite sense (lower) to conserve volume, not stay unchanged.