What is My Cloud Free Night?
My Cloud Free Night is a personalised weather forecast information service featuring products from Cloud Free Night for the benefit of the local astronomy and photography communities.
Where does the weather forecast come from?
My Cloud Free Night displays weather forecast information from the United States GFS global model. Forecast meteograms summarise the weather forecast over the next five days.
My Cloud Free Night displays official precis, town and district forecasts from the Australian Bureau of Meteorology and links to local (WeatherWatch, Oz Forecast) and overseas (Yr, Clear Outside, meteoblue, metcheck, 7Timer!) cloud forecasts to enable comparison of these weather predictions.
Where does the weather observations come from?
My Cloud Free Night displays Himawari-9 satellite images and cloud camera images. Satellite images originally processed by the Australian Bureau of Meteorology are from the geostationary satellite Himawari-9 operated by the Japan Meteorological Agency. Cloud camera images include links to the original image and source.
What is available in My Cloud Free Night?
Australian Bureau of Meteorology official precis, town and district forecasts for the next seven days.
Synoptic chart images of the latest mean sea-level pressure analysis and forecast map for next 4 days from the Australian Bureau of Meteorology.
GFS forecast meteograms: Hourly GFS meteograms for the next five days. Links to forecast meteograms from Oz Forecast, Yr, Clear Outside, meteoblue, metcheck and 7Timer!.
Himawari-9 satellite images.
Cloud camera (aviation weather cameras, all sky cameras, webcams) images, including links to the original image and source.
What is the GFS model?
The United States National Center for Environmental Prediction GFS (Global operational Forecast System) model covers the global domain at 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).
GFS model data for the next five days are downloaded (freely available for commercial use) from the NOMADS (NOAA Operational Model Archive and Distribution System).
When are GFS model forecasts updated?
GFS 12 UTC (3:30am-4:00am AEDT)
GFS 18 UTC (9:30am-10:00am AEDT)
GFS 00 UTC (3:30pm-4:00pm AEDT)
GFS 06 UTC (9:30pm-10:00pm AEDT)
What is Forecast?
Australian Bureau of Meteorology official precis, town and district forecasts for the next seven days. For further information, see Weather Data Services.
Precis forecast files in XML and town and district forecast files in PDF are downloaded (freely available for non-commercial use) from the Australian Bureau of Meteorology FTP Server. The precis forecast images for each forecast location are created from the forecast XML files. Every 30 minutes the precis forecast files are checked for any updates.
To display an official precis forecast, select the REGION (i.e. Victoria, SE Queensland) and LOCATION using the buttons to the right of the image. The map (including forecast district boundaries) and list of locations will be updated for the selected region. The location can also be selected from the displayed map. Selecting the forecast image will display the town (for locations in capital letters on the displayed map) or district forecast in a new window. Your selections for REGION and LOCATION will be remembered.
What is Chart?
Chart displays Australian Bureau of Meteorology chart images of the latest mean sea-level pressure analysis and forecast map for next 4 days. For further information, see Latest Colour Mean Sea-Level Pressure Analysis, Interpreting the Mean Sea Level Pressure (MSLP) Analysis and Colour Forecast map for next 4 days.
Synoptic chart image files in PNG format are downloaded (freely available for non-commercial use) from the Australian Bureau of Meteorology FTP Server. Every six hours the latest mean sea-level pressure analysis file is downloaded. The forecast map for next 4 days is downloaded daily.
What is Meteogram?
Meteogram images show a summary of GFS model forecasts over the next five days: Day 1 (+0 to +24 hours), Day 2 (+24 to +48 hours), Day 3 (+48 to +72 hours), Day 4 (+72 to +96 hours), Day 5 (+96 to +120 hours), Days 1-3 (+0 to +72 hours), Days 2-4 (+24 to +96 hours) and Days 3-5 (+48 to +120 hours) for particular locations. The meteograms (time-series graphs and tables) present detailed weather information. The graph/table displays hourly values of the temperature, moon phase, wind, wind gust, rainfall, humidity, fog, total, low, middle and high cloud cover.
GFS model data for the next five days are downloaded (freely available for commercial use) from the NOMADS (NOAA Operational Model Archive and Distribution System). The forecast meteogram images are created from the GFS model data and updated every six hours.
The meteograms show GFS hourly graphs of the total cloud cover, temperature, humidity, wind, rainfall, moon phase (% illumination) and moon/sun rise/set times; and tables of temperature, moon phase, wind, wind gust, rainfall, humidity, visibility, total, low, middle and high cloud cover for particular locations out to five days, to identify dark sky night opportunities. Dark sky night hours are defined by total 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.
To display a forecast meteogram, select the MODEL (i.e. GFS), DAY (i.e. Day 1, Day 2, Day 3, Day 4, Day 5, Days 1-3, Days 2-4 or Days 3-5), STATE (i.e. Victoria or Queensland) and location using the buttons to the right of the image. Your selections for MODEL, DAY, STATE and location will be remembered.
To display other meteogram forecasts for the selected location, select the source (i.e. OZ FORECAST, YR, CLEAR OUTSIDE, METEOBLUE, METCHECK or 7TIMER!) using the buttons below the image. The Oz Forecast (ADFD meteogram), Yr (detailed hourly forecast), Clear Outside, meteoblue (astronomical seeing), metcheck (astronomy) and 7Timer! (GFS meteogram) website pages will display in a new window.
Where are the Victoria meteogram locations?
Where are the Queensland meteogram locations?
What is Satellite?
Satellite images, updated every ten minutes, originally processed by the Australian Bureau of Meteorology from the geostationary satellite Himawari-9 operated by the Japan Meteorological Agency.
Satellite image files in TIF format over the Australian domain (85oE to 165oW and 55oS to 20oN) for Day + Night at 0.5 km resolution are downloaded (freely available for non-commercial use) from the Australian Bureau of Meteorology FTP Server. Satellite images over the last 24 hours are available from the Australian Bureau of Meteorology.
The satellite images are resampled over regions covering Australia (i.e. Victoria, Melbourne, SE Queensland and Brisbane).
The satellite images are displayed at their original resolution for specific map regions (i.e. Victoria and SE Queensland). The satellite images are zoomed (x4) for specific map regions (i.e. Melbourne and Brisbane).
To display a satellite image, select the REGION (i.e. Victoria, Melbourne, SE QLD or Brisbane) and TYPE (i.e. Day + Night or Visible Greyscale) using the buttons to the right of the image. Select the Show/Hide Location Names (Show Lon/Lat Grid) button below the image to toggle the display of location names and longitude/latitude grid over the satellite image. Step Forwards/Backwards through time, Move to the Earliest/Latest image or Start/Stop Animation of the images using the arrow buttons below the image. The default is to animate the satellite images over the last 3 hours. Adjusting the position of the slider will change the satellite image displayed and the length of the animation. The most recent 12 hours of satellite images can be displayed. Your selections for REGION, TYPE and Show/Hide Location Names will be remembered.
There are six satellite image types (Day + Night, Visible Greyscale, Infrared Greyscale, Infrared + Rainbow, Infrared + Zehr and Water Vapour) available from the Australian Bureau of Meteorology FTP Server.
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 Camera?
Camera displays cloud camera (aviation weather cameras, all sky cameras, webcams) images around Australia (nearly 500 locations and over 1000 camera images), including links to the original image and source.
To display a cloud camera image, select the REGION (i.e. Victoria, Melbourne, SE Queensland or Brisbane) and LOCATION using the buttons to the right of the image. The map and list of locations will be updated for the selected region. The location can also be selected from the displayed map. Selecting the cloud camera image or image source link will display the original image or image source in a new window. Your selections for REGION and LOCATION will be remembered.