Australian Government, Bureau of Meteorology

Cautionary Note

The times stated are in Standard Time (24 hour clock). During Daylight Saving Time (when in force) one hour needs to be added to the times stated.

Users of standard port tide tables should be aware that the heights and stream velocities are predictions that are prepared for average meteorological and oceanographic conditions and seasonal variations.

Tidal predictions for secondary ports are often based on limited observations. They are prepared by applying an adjustment to the time and height of tide in the appropriate standard port tide table. There are a number of adjustment procedures each of which is based on the statistical correlation between the tidal times and heights at the standard and secondary port. The correlation is never perfect. Accordingly the user must expect that the tidal predictions for the secondary port will be less accurate than those for the related standard port.

The actual water level height and stream velocity at both standard and secondary ports may vary when the meteorological and oceanographic conditions depart from the average.

Variations in tidal heights are mainly caused by unusually high or low barometric pressure, by prolonged strong winds or by large scale ocean currents, which can be predicted a few days in advance via the "Sea Level" links for each of the Forecast Regions on the Bureau's Sea Level Forecasts web pages.

Low-pressure systems tend to raise sea levels and high-pressure systems tend to lower them. The water does not, however, adjust itself immediately to a change of pressure. It responds, rather, to the average change in pressure over a considerable area.

The effect of wind on sea level and therefore on tidal heights and times is variable and depends on the geography/topography of the area in question. In general wind will raise the sea level in the direction towards which it is blowing.

A strong onshore wind will "pile up" the water and will cause the high waters to be higher than predicted. Winds blowing off the land will have the opposite effect.

© Australian Government 2010, Bureau of Meteorology