Help Logo General Questions

Where can I find sunrise & sunset times.

The authority which handles sunrise & sunset tables, moon phases and other astronomical data is THE AUSTRALIAN SURVEYING & LAND INFORMATION GROUP. Their web URL is: http://www.ga.gov.au/geodesy/astro/

Where can I find tide tables?

Tide tables are handled by the Bureau of Meteorology's NATIONAL TIDAL CENTRE. The URL is: http://www.bom.gov.au/oceanography/tides/

Where can I find wave and swell information?

Observations of sea swell height and direction are taken at a number of locations around the coast. Generally these are listed in the Coastal Weather Observations for each State or Territory and are updated several times each day. These products can be reached from the following links:

Charts showing swell height for all of Australia are also available to registered users as part of the Marine/Oceanographic Services bundle. Charges and registration are explained HERE.

Where can I find a colour satellite photo?

The Bureau currently only presents black and white images of cloud cover for general distribution. The Department of Electrical and Computer Engineering at James Cook University, Townsville has coloured images at: http://www.jcu.edu.au/JCUMetSat/web/metsat.html
The GMS-5 Satellite is a meteorological satellite and does not produce "true" color images. The Satellite looks at the Earth through 4 bands, one of which is considered a visible band. The visible band "sees" all wavelengths between 0.55 microns (mid green)and 0.75 microns (near infrared) but does not distinguish between them. The representation of this is a monochromatic image that meteorologists usually view in shades from black to white (high reflectance being white such as clouds and low reflectance as black such as sea and land). The other bands (which are all in the infrared) can be combined together to form a false colour image which is usually very pretty but nowhere near true color and is costly (time consuming) to produce (can be of the order of $120.00 Aust).
Low resolution GMS-5 data can be found in various places on the WWW (James Cook University as an example), but high resolution imagery is usually confined to the scientific community and other weather services due to the huge file sizes (of the order of 100Mbytes).

Why is the wind speed given in km/h instead of knots?

It is standard practice to use km/h (kilometres per hour) for public weather forecasts and observations and knots (nautical miles per hour) for coastal waters and high seas forecasts. (Knots is primarily a nautical term).

Do you have a list of Australian weather station locations on the web?

There are lists of stations available, but not through the menus on our web site yet. The address of the lists is: ftp://ftp.bom.gov.au/anon2/home/ncc/metadata/sitelists/
These are text files and the alphabetical lists for each State are those starting with 'sd'. Some stations are referred to by their secondary name, so you may have to use the search/find facility of your browser/editor to locate the name you are looking for.

Where can I find the definitions of wind strengths used in forecasts?

A web page explaining some of the descriptive terms for wind, rain, cloud and sea conditions is currently under construction. Basic wind speed values are as follows:
Light - 19km/h or less
Moderate - 20 to 30km/h
Fresh - 31 to 39km/h
Strong - 40 to 61km/h
Gale - 62 to 87km/h
Storm - 88 to 102km/h
Hurricane - 103km/h or more

Wind speed in knots is approximately half the km/h figure (1km/h = 0.54kts).

What is the difference between UTC and GMT time?

Universal Time Coordinates (UTC) is equivalent to Greenwich Mean Time (GMT). This is also equivalent to Zulu (Z) Time and is measured on the Prime Meridian (O degrees longitude) in Greenwich, England. By international agreement, the term UTC is recommended for all general timekeeping applications, and use of the term GMT is discouraged.
For more information on how this applies in Australia see the section on 'Timestamping' on our 'About Satellite Pictures' page at:

Where can I get international weather information?

Links to the official meteorological agencies of other countries can be found at the WMO web site.
Links to other weather related organisations can be found on the National Meteorological Library's "Meteorological Resources" page.

How can I get a Bureau of Meteorology calendar?

The Bureau of Meteorology Calendar, in most years, will be made available in late October. Details will be posted at http://www.bom.gov.au/calendar/

What is the Beaufort Wind Scale?

The Beaufort wind scale is used by mariners and meteorologists to indicate wind velocity. It was devised in 1805 by the Irish hydrographer Francis Beaufort.

Beaufort Scale - Wind Speed & Observed Effects
Force Knots Mph Kph Sea Term Sea Conditions On-land Appearance
0 <1 <1 <1 Calm sea like a mirror smoke rises vertically
1 1-3 1-3 1-6 Light air ripples with appearance of scales: no foam crests smoke drifts and leaves rustle
2 4-6 4-7 7-11 Light breeze small wavelets: crests of glassy appearance, not breaking wind felt on face
3 7-10 8-12 12-19 Gentle breeze large wavelets: crests begin to break: scattered whitecaps flags extended, leaves move
4 11-16 13-18 20-30 Moderate breeze small waves, becoming longer: numerous whitecaps dust and small branches move
5 17-21 19-24 31-39 Fresh breeze moderate waves, taking longer form: many whitecaps: some spray small trees begin to sway
6 22-27 25-31 40-50 Strong breeze larger waves forming: whitecaps everywhere: some spray large branches move, wires whistle
7 28-33 32-38 51-61 Near gale sea heaps: white foam from breaking waves begins to be blown in streaks trees in motion, resistance felt when walking
8 34-40 39-46 62-74 Gale moderately high waves of greater length: edges of crests begin to break into spindrift: foam is blown in well-marked streaks walking impeded
9 41-47 47-54 75-87 Strong gale high waves: sea begins to roll: dense streaks of foam: spray may reduce visibility structural damage may occur
10 48-55 55-63 88-102 Storm very high waves with overhanging crests: sea takes white appearance as foam is blown in very dense streaks: rolling is heavy and visibility is reduced trees uprooted, structural damage likely
11 56-63 64-72 103-117 Violent Storm Exceptionally high waves: sea covered with white foam patches: visibility still more reduced damage to structures wide spread
12 >63 >72 >117 Hurricane air filled with foam: sea completely white with driving spray: visibility greatly reduced severe structural damage to buildings, wide spread devastation, flooding

Why is the product I want "old"?

The weather charts, satellite images, radar images, forecasts and warnings are all updated regularly and automatically. There are occasional system faults, but if you are seeing old products its most likely that you are having a problem with caching.
Either your browser is holding an old version of the product you want and not fetching a new one from our site. Make sure you click on "Refresh" / "Reload" (whichever is appropriate for your browser).
Holding down the shift key while clicking on "Refresh" / "Reload" does direct some browsers (certainly Netscape) to not check their local cache first but re-fetch the document over the network.
Or your Internet Service Provider (ISP) is caching (keeping a copy of the web pages) on their server(s). You may have to contact your ISP.

What is a Precis Forecast?

A precis is a summary. For some purposes a full forecast with descriptions of the expected temperature, rainfall, wind, cloud, visibility and humidity is too long, so we also prepare precis forecasts. Generally a precis forecast contains just a few words describing the most significant weather element expected and a temperature.

Daylight Saving Time

Please use the following link for details on the current Time Zones in Australia
Australian Time Zones - with Daylight Saving details

Past Implementation Dates of Daylight Savings Time within Australia.

The various State/Territory contacts for Daylight Saving responsibility.