New Weather Services: Frequently Asked Questions

City and Town Forecasts:

District Forecasts:

Marine Forecasts:

ACT and Canberra Forecasts (Updated 17/11/2010)

Snowy Mountains Area Forecasts

1. What is changing?

The Bureau of Meteorology is implementing a new forecasting system aimed at expanding services to the NSW and the ACT public. The system allows the Bureau's forecasters to develop 7 day forecasts graphically, by "painting" the forecasts on their screen, and saving them into a database of 6km grids. The information that is stored in this database is then used to automatically generate text forecasts, although our forecasters can edit this text if required.. This increases the number of locations that a forecast can be generated for by removing the need for manually produced text forecasts.

Forecasters will be able to easily apply their local knowledge across all areas of the state to provide the best possible forecast for the community.

The output database of forecasts is called the Australian Digital Forecast Database (ADFD).

2. How will the forecasts change?

Forecasts produced by the new forecasting system will provide more detailed information of those weather elements that are important to the Australian public.  This includes an expanded description of sunshine, cloud cover and rainfall, greater detail of expected wind conditions, and greater clarity of expected temperature for our forecast districts.

3. When will the Forecast Explorer be available in NSW?

The Bureau has planned to release each part of the new system in phases to ensure that new products are of the highest quality. The Bureau released the NSW & ACT graphical output from the Australian Digital Forecast Database late in July 2011. The graphical forecasts will be displayed on the Bureau’s website using an interactive display tool called the Australian Forecast Explorer.  The Forecast Explorer will allow people to view forecasts graphically for various times over the next 7 days. Try the Forecast Explorer now.

4. Why doesn't my forecast print out on a single page?

With the move to providing more information, there are some forecasts that no longer fit on a single page. The Bureau recognises that this may cause some inconvenience. We are working hard to develop improved displays for our forecast information. If you have any issues with the new services, please send feedback.

City and Town Forecasts

5. Why doesn’t my town receive a forecast?

With the launch of the new system we have increased the number of forecast locations from 57 to 68. The selection of the new locations was based on population and geography to achieve a more equitable spread across the state. The list of official forecast locations will be reviewed next year.

Within a few months we will also be providing our forecast database online via the NSW & ACT Forecast Explorer.  Using this map interface people will be able to find, display and zoom into weather details for their area down to the 6 kilometre grid scale by point and click. For a preview, try the Victorian Forecast Explorer.

6. When are the forecasts issued?

To allow for the large increase in services the Bureau is moving nationally towards two major issues per day at around 5am and just after 4pm for all forecasts. The Bureau’s forecasters will update forecasts promptly if conditions change. See the list of forecast issue times.

7. What does "rainfall total" mean?

The rainfall totals are issued for single points (e.g. Sydney City, Canberra City or Thredbo) and represent the likely rainfall amount for a 24 hour period. Sometimes rain falls in a quite patchy pattern across an area with some locations receiving much more rain than other places nearby. For example, when showers or thunderstorms are expected the rainfall totals are rarely uniform.  Some locations may receive a heavy shower and while others miss out completely. On these days the rainfall range will be quite broad, eg 5 to 40 mm  When steady rainfall is expected over a wide area the range will be narrower, eg 20 to 30mm.

8. What does the "chance of rain" mean?

The chance of rainfall is expressed as a percentage and is a new service to the majority of the NSW public. It describes the likelihood of receiving a measureable amount of rain during the day at a point. If for example the chance of rain for Sydney City is 70%, on 7 out of 10 days with similar weather conditions rainfall will be measured in the Sydney rain gauge.. In the Sydney Metropolitan forecast, the chance of rain is provided at both Sydney City and Penrith to account for the wide range in rainfall that can occur across the metropolitan area.

We are also including the "chance of no rain", at least initially, because research into community understanding of this type of service has shown that it can be misunderstood. If both the "chance of rain" and its opposite, the "chance of no rain" is provided, people are more likely to interpret the information correctly.

At this stage, only Canberra, Sydney and the Alpine Centres receive the rainfall information. Rainfall information has been provided in the Canberra and the Snowy Mountains forecasts for a number of years. We are extending the service to Sydney first and, with further development of forecasting techniques, we plan to provide this rainfall information at all of our forecast locations

District Forecasts

9. Why have some district boundaries changed?

There have been adjustments to the boundaries of some southern NSW districts.  See the map showing the old and new boundaries. The new Snowy Mountains zone will allow more precise descriptions of weather conditions.  The Riverina District now follows the Local Government Boundaries and matches the Rural Fire Services Riverina Fire Areas.  Previously the eastern boundary of the Riverina ran though the centre of both Wagga Wagga and Albury. Both these regional centres will now lie within the Riverina District. 

10. Where are the observations for my town?

The Latest Weather Observations for New South Wales are listed in a table grouped by weather district. Following the changes to the district boundaries, the observations for some locations will now be found in a different part of the table. See the list of locations which have changed districts.

11. Why does my town say the "chance of a shower" but the broader district forecast does not mention rainfall?

The point forecasts are generated by sampling the expected weather at a single location and the districts forecasts sample a wide range of locations. When summarising wide areas of the NSW or the ACT, sometimes the areas of rainfall are so small that to mention them would paint the wrong picture for most residents.

Marine Forecasts

12. Why have the marine zones changed?

The Bureau has responded to ongoing feedback from the coastal communities and redefined some of its coastal waters zones. The new system provides the opportunity to extend services and the additional forecast zones will provide mariners with more detailed coastal waters forecast information between Gabo Island and Ulladulla, and between Seal Rocks and Wooli.   The Bureau consulted with marine stakeholder groups including NSW Marine Rescue and NSW Maritime to determine the best approach.  The new names were chosen to identify either the major port in each zone (Macquarie, Coffs, Batemans, Eden) or the most significant feature within the zone (Byron). More information.

13. Why is the wind information in the written forecast sometimes different to the Forecast Wind for Marine Areas Maps?

These wind forecast maps are produced from computer models and may not always reflect official forecasts, especially in the vicinity of weather fronts, east coast lows or in rapidly changing conditions. As they contain no input from weather forecasters, it is important to check the Bureau's marine forecasts and warnings.

Within a few months there will be official wind and wave forecast maps provided via a new marine version of the Forecast Explorer. 

14. What is combined sea and swell?

Combined sea and swell is also known as total wave height, or significant wave height. Combined sea and swell describes the combined height of the sea and the swell that mariners experience on open waters, and equates approximately to the average wave height of the highest one third of the waves. A lookup table has been developed to outline how to calculate the Combined sea and swell.

15. Where is the Sydney Weekend Boating Forecast?

There are now Sydney Local Waters forecast maps which aim to provide more detail than the Sydney Weekend Boating Forecast service and will be issued every day of the week. As we gather feedback we will work to fine tune the service.

16. Why does only Sydney receive a Local Waters forecast?

The Bureau is staging service enhancements to maintain high levels of quality. Additional local waters forecasts for other areas, for example Lake Macquarie, are planned but the timing remains uncertain.

17. Why don't the wave heights on the Sydney Local Waters Forecast vary?

Anyone familiar with boating around Sydney will have experienced the vagaries of weather. The varying size and exposure of the local waters areas means that under differing wind conditions there is wide variation of the sea state but generally this is below 0.5m.  Those areas exposed to the open ocean will experience bigger waves and we will aim to include these in our forecasts.

ACT and Canberra Forecasts

18. Where is the " Weather Situation"? Updated 17 November 2010

The format of the Canberra Forecast is now the same as the Sydney forecast.  The descriptive summary of the current weather situation and future developments is available in the new ACT Forecast.

19. Where are the "Winds on lakes"?

The Canberra forecast now provides the forecast windspeed in km/h for all 7 days.  This windspeed is representative of the wind on the lakes.

20. Why is there no longer a Small Boat Alert?

Feedback from the community indicated that this alert was no longer required.  The new forecast provides the forecast windspeed in km/h for all 7 days.

Snowy Mountains Area Forecasts

21. Why has the alpine definition above 1200m been removed?

The Bureau's new design for services in the highlands of the southeast of the State is a broad district type service catering for residents and visitors to the Snowy Mountains Region. In addition the Bureau has introduced a 7 days Alpine Centres forecast, initially covering Thredo Top Station and Perisher Valley.

As the new services are consolidated in the coming months, the Bureau will be in a position to further fine tune and develop the services to the Snowy Mountains region.

22. Why are the snow depth observations no longer provided on the Snowy Mountains Forecast?

The snow depths are measured by SnowyHydro and are available on its website and some alpine resort websites.

23. Where are the rainfall forecasts that used to be provided in the Snowy Mountains Region Forecast?

The chance of rain and rainfall total forecasts are provided in the Alpine Centres Forecast. This information will also be available for many more locations once the new graphical services are launched later in the year.

24. How can there be a higher likelihood of snow at 1000m than at 1400m? Doesn't it get colder as you go up?

The snow probabilities on these forecasts are a combination of the probabality of there being a system that will produce precipitation and the probability of the conditions being cold enough for this precipitation to fall as snow. Sound complex? It is but in some situations moisture is locked at lower elevations hence snow is more likely there, even though it’s colder above.