Another marine phenomenon which can cause inundation of low lying coastal areas is the storm surge. This is a raised dome of water about 60 to 80 km across and typically about 2 to 5m higher than the normal tide level. If the surge occurs at the same time as a high tide then the area inundated may be quite extensive. The general name given to cyclone Watch and Warning messages is an Advice or Tropical Cyclone Advice. The TCWC issues these messages and liaises with the police, State and Territory Emergency Services and the media.
Tropical cyclones develop from tropical depressions.
They are formally designated tropical cyclones and named when winds of at least gale force have developed. The name given to a system at this time is used throughout its life. Immediately it is recognised that a cyclone might endanger life or property of coastal or island communities within 48 hours, the Bureau's public warning system is activated. A tropical cyclone or developing depression that does not threaten any coastal or island communities will be mentioned only in the Bureau's weather notes and in advice to shipping and aviation. A cyclone watch is issued if a cyclone or potential cyclone exists and there are strong indications that winds above gale force will affect coastal or island communities within 24 to 48 hours of issue.