A Tsunami Warning may be issued once there is high degree of confidence that a tsunami threat exists based upon detection that a tsunami has been generated; or if there is a potential threat (unconfirmed) to NSW within the next 90 minutes. This warning will outline the areas under threat using coastal waters forecast districts and the actions that should be taken by the community. Warnings are stratified to give some indication of tsunami magnitude. Tsunami warnings may be issued for the NSW mainland coast and/or Lord Howe Island. Tsunami Warnings are issued by the Bureau of Meteorology and are distributed to all media outlets and emergency management agencies. The following specific warning classes exist: (1) Marine Environment and Immediate Foreshore Threat: The tsunami is expected to mainly affect the marine environment for specified coastal areas. Although major land inundation is not expected, there may be local amplification of the tsunami in some areas leading to land inundation in limited low-lying coastal areas. Significant sea level variations, may continue for many hours and even days along the affected coastal areas. Strong rips and currents may result in extreme danger to people in the water. Potential for damage to marine facilities and craft in marinas and harbours. Potential for sea water intrusions to the top of the beach, minor overtopping of sea walls and even over very low lying foreshore areas paths, roads, beachfront car parks etc. (2) Major Land Inundation Threat: Major sea level variations along the affected coastal areas. Significant over-topping of foreshore dunes and sea walls, with areas of inundation beyond the immediate foreshore. Extreme danger extending beyond the water to low lying coastal areas. Probable extensive damage to ports, marina and small boats. Potential damage to buildings and infrastructure near the shore. Extremely dangerous affects in the water continuing for many hours and even days. Tsunami Warnings can be cancelled if the situation is reassessed as having no threat, or at a point following an event at which the situation is assessed as posing no further threat