What is Cloud Free Night?

Cloud Free Night is an online weather forecast information service, for the benefit of the Australia & New Zealand astronomy and photography communities. It is unique in offering a comparison of the widely available forecasts from the United States GFS global model with higher resolution forecasts from the Australian Bureau of Meteorology ACCESS model.

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"Running an observatory taking people out on a monthly basis using CFN is my goto. This weekend in Perth it was crazy weather, tornadoes, hail and rain. Using the metorogram the group threaded the needle and got perfect clear skies and 10 hours of imaging time and just as we finished packing up to go home it started raining" - Brendan Mitchell, Astronomy Academy Perth (1 September 2019)

"The usability is great on my iPhone, your invaluable site has led to many successful adventures when conventional predictions were inaccurate and pessimistic. Keep up the amazing work, your users love each and every improvement you are making!" - Kevin Lurie, Cloud Free Night Facebook post (29 July 2019)

"Thanks for including Ulladulla in the meteogram ... I'm currently imaging NGC 6744 galaxy down near Ulladulla ... Beautiful night and as usual CFN is spot on ... CFN , an important part of my Astro tool kit ... Thanks very much" - IceInSpace Member Startrek (Martin) (9 July 2019)

"A superbly practical tool with the local Access model for planning public and school events, astro field trips for observation collection, and knowing whether to get out of bed to try seeing something that's pre-dawn. Over the years since it was first developed and trialled, it's always been by far the most reliable predictor for the Mornington Peninsula region, including the Briars observatory. Three cheers for Robert, Phil et al." - Peter Skilton, Mornington Peninsula Astronomical Society (13 March 2019)

Where does the weather forecast come from?

Almost every weather website and app you have ever heard of is providing data from the United States GFS model, because it is freely available, even for commercial use, allowing anybody around the world to resell weather services using the same underlying data. However, as a global model, this is far from the best source of forecasts for the Australian region and New Zealand, particularly for short-term outlooks.

Cloud Free Night is the only service currently providing detailed cloud forecast information from the Australian Bureau of Meteorology ACCESS model which includes higher resolution regional and city models. Forecast maps over specific Australian regions and New Zealand, and meteograms summarising the forecast over the next ten days for particular locations are available. The maps allow you to toggle between the GFS and ACCESS models at any point while the meteograms present detailed cloud information or a summary comparison of the two models.

Where does the weather observations come from?

Cloud Free Night displays the latest Himawari-8 satellite images and radar images via the Australian Bureau of Meteorology. The high-definition satellite images are available over many areas covering the Australia and New Zealand regions. The radar images are presented using a modified colour palette for greater clarity.

What is available in Cloud Free Night?

ACCESS-C city (i.e. -VT, -SY, -BN, -DN, -PH, and -AD) hourly (+0 to +36 hours) model forecasts (1.5 km resolution) updated 4 times/day (00, 06, 12 and 18 UTC) (Australia only);
ACCESS-R regional hourly (+0 to +72 hours) model forecasts (12 km resolution) updated 4 times/day (00, 06, 12 and 18 UTC) (Australia and New Zealand);
ACCESS-G global 3-hourly (+75 to +120 hours) and 6-hourly (+126 to +240 hours) model forecasts (25 km resolution) updated 2 times/day (00 and 12 UTC); and
GFS global hourly (+0 to +72 hours) and 3-hourly (+75 to +240 hours) model forecasts (28 km resolution) updated 4 times/day (00, 06, 12 and 18 UTC).

Hourly ACCESS-C (+0 to +36 hours), ACCESS-R and GFS (+0 to +72 hours); 3-hourly ACCESS-G (+75 to +120 hours) and GFS (+75 to +240 hours); and 6-hourly ACCESS-G (+126 to +240 hours) Total Cloud, Fog (ACCESS only), Low Cloud, Middle Cloud, High Cloud, Wind, Jetstream, Pressure/Rainfall, Pressure/Evaporation (ACCESS only), Temperature, Humidity, Precipitable Water and Solar Irradiance forecast maps.

Victoria, New South Wales, Australian Capital Territory, SE Queensland, Northern Territory, SW Western Australia, South Australia, Tasmania, Melbourne, Sydney, Canberra, Brisbane, Darwin, Perth, Adelaide and Hobart ACCESS-C; and Australia, SE Australia, Victoria, New South Wales, Australian Capital Territory, SE Queensland, North Queensland, Far North Queensland, Northern Territory, Central Australia, NW Western Australia, SW Western Australia, South Australia, Tasmania and New Zealand ACCESS-R, ACCESS-G and GFS forecast map regions.

Hourly (Day 1, Day 2) ACCESS-C; 3-hourly (Days 1-3 and Days 3-5) ACCESS-R, ACCESS-G and GFS; and 6-hourly (Days 5-10) ACCESS-G and GFS forecast (Dark Sky, Cloud, Solar and All) meteograms (TBC meteogram locations).

Himawari-8 satellite images updated every 10 minutes for the Australian Region, Australia, SE Australia, Victoria, Melbourne, New South Wales, Sydney, Australian Capital Territory, Canberra, SE Queensland, Brisbane, North Queensland, Far North Queensland, Coral Sea, Northern Territory, Darwin, Central Australia, NW Western Australia, SW Western Australia, Perth, South Australia, Adelaide, Tasmania, Hobart, Tasman Sea, New Zealand, North Island and South Island map regions.

Radar images updated every 6 or 10 minutes for 64km, 128km, 256km and 512 km ranges (Australia only) for 57 radars from the Bureau of Meteorology radar network.

Synoptic chart images, updated every 6 hours, of the latest colour mean sea-level pressure analysis (including satellite image background) from the Bureau of Meteorology.

What is Map?

Map images show ACCESS-C, ACCESS (ACCESS-R or ACCESS-G) or GFS hourly, 3-hourly or 6-hourly forecasts over specific regions for the next ten days. The maps display forecasts of Total Cloud, Fog (ACCESS only), Low Cloud, Middle Cloud, High Cloud, Wind, Jetstream, Pressure/Rainfall, Pressure/Evaporation (ACCESS only), Temperature, Humidity, Precipitable Water and Solar Irradiance for Victoria, New South Wales, Australian Capital Territory, SE Queensland, Northern Territory, SW Western Australia, South Australia, Tasmania, Melbourne, Sydney, Canberra, Brisbane, Darwin, Perth, Adelaide and Hobart map regions (ACCESS-C); and Australia, SE Australia, Victoria, New South Wales, Australian Capital Territory, SE Queensland, North Queensland, Far North Queensland, Northern Territory, Central Australia, NW Western Australia, SW Western Australia, South Australia, Tasmania and New Zealand map regions (ACCESS-R, ACCESS-G and GFS).

What is the ACCESS model?

Australian Bureau of Meteorology Australian Community and Earth-System Simulator (ACCESS) models:
ACCESS-C city (i.e. -VT, Victoria/Tasmania; -SY, Sydney;, -BN, Brisbane; -PH, Perth; -AD, Adelaide; -DN, Darwin) (1.5 km resolution), with hourly forecast parameters out to 36 hours, updated 4 times per day (00, 06, 12, 18 UTC);
ACCESS-R regional (12 km resolution), with hourly forecast parameters out to 3 days (+72 hours), updated 4 times per day (00, 06, 12, 18 UTC); and
ACCESS-G global (25 km resolution), with three hourly forecast parameters out to 10 days (+240 hours), (some parameters only available 6-hourly past +120 hours), updated 2 times per day (00, 12 UTC);
freely available (in real-time) for non-commercial use at the Bureau of Meteorology OPeNDAP server.

When is ACCESS model data updated?

ACCESS-C 12 UTC (01:15-03:15)
ACCESS-R 12 UTC (01:00-04:00)
ACCESS-G 12 UTC (05:15-06:45)
ACCESS-C 18 UTC (07:15-09:15)
ACCESS-R 18 UTC (07:00-10:00)
ACCESS-C 00 UTC (13:15-15:15)
ACCESS-R 00 UTC (13:00-16:00)
ACCESS-G 00 UTC (17:15-18:45)
ACCESS-C 06 UTC (19:15-21:15)
ACCESS-R 06 UTC (19:00-22:00)
(Melbourne/Sydney local time)

What is the GFS model?

United States National Center for Environmental Prediction Global operational Forecast System (GFS) model:
GFS global (28 km resolution), with hourly forecast parameters out to 5 days (+120 hours) and 3-hourly forecast parameters out to 10 days (+240 hours), updated 4 times per day (00, 06, 12, 18 UTC), freely available (in real-time) for commercial use at the NOMADS (NOAA Operational Model Archive and Distribution System).

When is GFS model data updated?

GFS 12 UTC (03:30-05:15)
GFS 18 UTC (09:30-11:15)
GFS 00 UTC (15:30-17:15)
GFS 06 UTC (21:30-23:15)
(Melbourne/Sydney local time)

What is Meteogram?

Meteogram images show a summary of ACCESS and GFS forecasts over the next ten days (Day 1, Day 2, Days 1-3, Days 3-5 and Days 5-10) for particular locations (TBC meteogram locations). The (Dark Sky, Cloud, Solar and All) meteograms (time-series graphs and tables) present detailed cloud information or a summary comparison of the two models. The table displays hourly, 3-hourly or 6-hourly values of the temperature, rainfall, wind, jetstream, pressure, humidity, evaporation, solar irradiance, fog and total, low, middle and high cloud cover.

The Dark Sky images show, meteogram-style, ACCESS and GFS hourly, 3-hourly or 6-hourly values of the total cloud cover forecast and moon phase (% illumination), and moon/sun rise/set times for particular locations out to ten days, to identify dark sky night opportunities. Dark sky night hours are defined by cloud cover < 20% and moon illumination < 50% (or no moon), and are displayed using star icons near the top of the graph and in the table.

Where are the Victoria meteogram locations?

Where are the New South Wales meteogram locations?

Where are the Australia Capital Territory meteogram locations?

Where are the Queensland meteogram locations?

Where are the Northern Territory meteogram locations?

Where are the Western Australia meteogram locations?

Where are the South Australia meteogram locations?

Where are the Tasmania meteogram locations?

Where are the New Zealand meteogram locations?

What is Satellite?

Satellite images originally processed by the Bureau of Meteorology from the geostationary satellite Himawari-8 operated by the Japan Meteorological Agency, updated every ten minutes, freely available (in real-time) for non-commercial use at the Bureau of Meteorology FTP Server. The high-definition satellite images are available over many areas covering the Australian region (including New Zealand).

Day + Night: True-colour images (1 km resolution) based on reflected visible light. These are useful, for example, for identifying fog and low cloud, which may not be visible in thermal infrared images because it has a similar temperature to the ground below. The visible light images only show parts of the Earth that are in daylight. Areas with no sunlight to reflect are replaced with greyscale thermal infrared imagery. To match the familiar colour of clouds, the infrared imagery colour table is inversed, which shows cloud as shades of white.

Visible Greyscale: Greyscale images (0.5 km resolution) based on one single visible wavelength (in comparison to the true colour image which combines three). These images will appear black in regions of no sunlight, i.e. night-time. Visible images are a record of the visible light scattered or reflected towards the satellite from the Earth and clouds. They give meteorologists extra information that may not appear on infrared images. For example, fog appears in visible images, but may not show up in infrared images as its temperature is very close to that of the land below. Visible images are only available during daytime, as at night there is no reflected sunlight.

Infrared Greyscale: Infrared (IR) images (2 km resolution) are derived from radiation emitted from the Earth and its atmosphere at thermal-infrared wavelengths (10-12 um). These images provide information on the temperature of the underlying surface or cloud. IR images are available 24 hours per day because temperatures can always be measured. This is in contrast to visible images, which are only available during daylight hours. Temperatures are represented by a greyscale, where black and white represent the hottest and coldest areas respectively. As clouds tend to be cooler than the ground or sea below (not always the case for low-lying clouds), they appear as light grey to white, making IR images simple to compare with visible images.

Infrared + Rainbow: Colour-enhanced images (2 km resolution). To assist in interpreting greyscale IR images, methods can be used to colour all pixels representing a particular temperature range. The temperature of clouds is associated with their height, so highlighting certain temperature ranges is useful for estimating the height of the observed clouds. These precision of these temperature measurements are within one or two degrees Celsius. Images coloured in this way are known as 'false colour' images.

Infrared + Zehr: Colour-enhanced images (2 km resolution). Ray Zehr from the US National Oceanic and Atmospheric Administration developed the Zehr enhancement, which applies temperature colour ranges to the cold end of the scale. This highlights deep convection that is generally associated with tropical cyclones and thunderstorms. These images can be useful in tracking the movement of tropical cyclones.

Water Vapour: Colour-enhanced images (2 km resolution) showing a measure of the amount of water vapour contained in the mid to upper levels of the troposphere. These images can be used to determine moisture advection (horizontal transport from one region to another), vertical movement of air (rising and sinking or air) and synoptic features such as short wave troughs, ridges and jet streams. Colour-enhanced imagery helps to show how saturated an area is.

What is Radar?

Radar images updated every 6 or 10 minutes for 64km, 128km, 256km and 512 km ranges (Australia only) for 57 radars from the Bureau of Meteorology radar network, freely available (in real time) for non-commercial use at the Bureau of Meteorology FTP Server. The radar images are presented using a modified colour palette for greater clarity.

What is Chart?

Synoptic chart images, updated every 6 hours, of the latest colour mean sea-level pressure analysis (including satellite image background) from the Bureau of Meteorology, freely available (in real-time) for non-commercial use at the Bureau of Meteorology FTP Server.

How does the Cloud Free Night service operate?

Cloud Free Night is operated by a small team from the Australia astronomy community. The Cloud Free Night service is hosted on a leased (Binary Lane), self-managed Linux Virtual Private Server (VPS), with IDL® (Harris Geospatial Solutions) installed and licensed (esri Australia). IDL® applications are run automatically to download (using OPeNDAP) the ACCESS and GFS model data, and Bureau of Meteorology Himawari-8 satellite and radar images, to produce the forecast maps, meteograms, satellite and radar images available from this VPS-hosted website. IDL® is a registered trademark of Harris Geospatial Solutions for their Interactive Data Language software, used by astronomers worldwide. Esri Australia is the official local distributor of IDL®.

How can I contact the Cloud Free Night team?

Cloud Free Night is operated by a small team from the Australia astronomy community. Please contact us info@cloudfreenight.com if you would like a meteogram for your home town location or your club's observing site. We would like to hear of your experience in using, or suggestions to improve, the Cloud Free Night service.

How can I support the Cloud Free Night service?

Cloud Free Night is a completely free service, funded by previous donations from the Australia & New Zealand astronomy and photography communities. Images in the web page footer acknowledge those organisations who have supported Cloud Free Night in the past. Please consider donating to support the development and maintenance of the Cloud Free Night service. Contributions to help cover running costs are most welcome.