The water level and hence tidal streams is much affected by the direction and duration of the winds. West to south-west winds cause a rise in sea level outside Port Phillip and a consequent increase both in rate and duration of ingoing stream will continue till sea levels inside and outside have reached equality, then the increased ingoing stream will cease and the streams become normal. On the winds ceasing, sea level outside falls to normal, causing the outgoing stream to increase both in duration and rate till sea level in Port Phillip has fallen to normal and the levels outside and inside are again equal. These surges can reach negative 0.2m and positive 0.4m. Greater variations have been recorded.
Surges can be present for a number of days or be short term only.