The official local waters wind and wave forecast maps show official forecast information of winds and waves issued by the Bureau of Meteorology in a map display. Animation controls allow the maps to be displayed in a 3-hourly time sequence. Two options are available to display the maps, a single map option or a side by side option.
Maps can be animated by using the arrow controls above the image to play, stop, step forward, and step back within the sequence. Individual time steps can be selected using the panel above the map. These times are for Eastern Standard Time using a 24-hour clock. i.e. the number 10 corresponds to 10am, and 14 is for 2pm.
The date and time of each forecast map is labeled above the map and is given in local time. The information on these maps is created twice daily around 5am and 5pm.
About the data
The wind forecasts are for average wind speed and direction at the standard height of 10 metres above sea level. The average wind is for a 10-minute period. Wind consists of gusts and lulls, and wind gust speeds are typically 30 to 50 per cent higher than the average wind speed. Stronger gusts are likely in the vicinity of squalls, showers, thunderstorms and frontal systems.
Wind speed is indicated by colours and is specified in knots. A knot is the standard international unit of speed used in maritime navigation, and is one nautical mile per hour. The conversion from knots to other units can be calculated at http://www.bom.gov.au/lam/calc.shtml.
It is important to understand how the colours on these maps relate to official Wind Warning levels as defined at http://www.bom.gov.au/marine/about/marine-definitions.shtml. It is recommended to check for official wind warnings issued by the Bureau of Meteorology when planning or conducting any water based activities.
Wind direction is indicated by the direction that the arrow is pointing to. For example an arrow pointing towards the top of your computer screen (↑) is blowing from the south to the north. In a worded forecast or in a radio broadcast this would be referred to as a southerly wind.
Wave height forecasts are available for the combined sea and swell height. The wave height is given in units of metres and is the distance from the trough of the wave to the crest.
The Combined sea and swell height (commonly called 'significant wave height') represents the average of the highest one-third of the waves. This Combined sea and swell height is used in official Wind Warnings.
Waves are generally organized in sets of waves with groups of smaller waves in between each set. The highest waves can be up to 50% higher than the average heights displayed on these maps. Interestingly, a wave height double the heights displayed on these maps can be expected approximately 4 times a day.
Source of the data
The forecast wind and wave maps use information sourced from the Australian Digital Forecast Database, developed by Bureau of Meteorology forecasters. (About graphical forecasts). The descriptive forecasts for the Local Waters and Coastal Waters areas are based on information available in these maps.