The Australian Weather News 3-hourly weather reports give possibly the most comprehensive and detailed view of current Australian weather available. Colour-coding and symbols pack an enormous amount of information into a small space, but allow you to home in on what's interesting. The reports use the traditional table format, with one row per station report, but colour is used to highlight significant parts of each observation while symbols give full information about cloud, weather and even the barograph trace. It's in a form that is easy to understand but doesn't dumb down the information so as to make it fit the page! There's a description of each column of information below.

The reports are based on the synoptic observations -- or obs -- sent in every three hours by hundreds of professional and volunteer observers around the country. They are supplemented by an expanding network of automatic weather stations. However, the reports from manned stations are considerably more detailed than the hourly automatic weather station reports, giving visual observations of cloud types and amounts, descriptions of present and past weather and measurements of visibility, as well as occasional comments on the weather. They provide the main surface input for the Bureau of Meteorology's weather maps and analysis, and for the global computer forecasting models run by many countries.

To pack all this information onto a computer screen in a form that mere mortals can understand is something of a challenge. About 7,000 obs are received each day from airports, lighthouses, post offices, remote cattle stations and country town backyards. While temperature, barometric pressure, wind, humidity and rainfall can be summarised in figures, it is the visual observations of the human observers that are often the most interesting but most difficult to represent. For example, how do you fit this in a concise report: "Over the past few hours it was cloudy with a few sunny breaks at first, but then thunderstorms developed but have cleared away to intermittent moderate rain now. The sky is a mix of thick nimbostratus with some very low-based large cumulus moving in from the west."

I have decided to use the standard international weather symbols, the same as used on the AWN synoptic charts (and on professional synoptic analysis charts around the world). Many of the weather symbols are pretty self-explanatory. looks like rain, and looks like heavier rain! is a thunderstorm, is snow, drizzle, fog, cumulonimbus cloud, and so on. However, observers can use 99 symbols to describe just the present weather alone, so you'll find a few less intuitive ones, such as and . Happily, you can refer to cheat cards to see what the more obscure symbols mean -- just click on the column heading to bring it up in a separate screen.

The same information is available in three formats, depending on how you want to use it.

• The state weather reports give all observations for each state for each observation time. Click on latest for the most recent obs time, or go the the archive for all 3-hourly obs from the past week. These are good for getting a snapshot of the weather at any one time.

• The district full-day reports gradually accumulate through the day all the observations for each weather station in the district into one table. These are good for seeing the progress of the weather over time. There are also grouped reports of capital city and regional centres available. Again, there is a one-week archive for each district.

• Finally, the National Severe Weather Summary lists only those observations which show that significant weather is happening. It is updated about every 15 minutes, and can get quite colourful when the weather gets wild.

The format for all reports is basically the same, and tries to reduce the problems that some users with small screens will have by dividing the information into two, with the station names down the middle. To the left of the station names are the basic daily measures of maximum and minimum temperature and rainfall. Where averages are available, the departure from average is shown, while rainfall is often given over two different periods such as 3 and 6 hours. To the right of the station name are the instantaneous observations made by the observer in the 10 minutes leading up to obs time -- cloud, weather and instrument readings.

I hope you have as much fun using the tables as I've had creating them. If they seem a bit colourless today, just wait until the weather gets interesting!

Max

The maximum temperature over various periods. At 9am, it is the official 24-hour maximum. At 3pm, it is the maximum since 9am. AWS, and some manned stations, also report a maximum at midnight which is for the previous 24 hours. When the temperature reaches 43 degrees, the cell turns red.

The minimum temperature over various periods. At 9am, it is the official 24-hour minimum. AWS and some manned stations also report a minimum at midday which is for the previous 24 hours. When the temperature reaches -6, it turns blue, probably along with the inhabitants.

The variation from normal max or min temperature, where the station has been operating long enough to have credible averages. These columns make great use of colour coding to show readings both above and below normal for both max and min temps.

The grass or terrestrial minimum temperature overnight. This is recorded by a minimum thermometer placed so that it is just touching the top of short-clipped grass, and gives a more accurate indication of the occurrence of frost than the standard minimum temperature thermometer which is exposed in a Stevenson Screen about 1m above ground level. On clear, calm winter nights, there can be some astounding differences between these two thermometers. This also turns blue when it reaches -6.

When rain has fallen, the observer often records the amounts for two different periods, so 2/24 0.6/18 indicates 2mm for the past 24 hours and 0.6mm over the past 18 hours. Tr = a trace of rain (less than 0.1mm, but enough to empty out of the gauge). The cells turn tasteful shades of green when the rainfall rates reach the following levels:

The official name of the station

So, for example, 0331=31 March

The clock time the observation was made. The standard synoptic hours in Australia are 0000, 0300, 0600, 0900, 1200, 1500, 1800 and 2100 in whatever local flavour of time is current, whether daylight saving or standard time. Yes, Hilda, this means that observations are not synchronous across the country. You will notice that some stations (mostly AWS) make some intermediate hour observations as well. These are taken so as to synchronise with the global observing network at 00, 03, 06, etc UTC.

Time for some symbols! For a full explanation of them, click here, or click the column heading in the report. For more information on clouds, go to the AWN Visual Observation page.

If you like clouds you will love the detail in this box. There are six items of information. From the left:
1. ... show increasing amounts of total cloud cover. The circle is like the dome of the sky above you, and the cloud amount is measured in eighths (or octas) of the sky covered. If the observer can't ascertain the cloud cover, you get an
2. A second cloud amount symbol tells you how much of the sky is covered by the lowest type of cloud (usually low level cloud, but sometimes middle level cloud).
3. Next to the low cloud amount symbol is a low cloud type symbol, e.g. . There are nine possibilities, and they tell you a lot about the character of the weather at the station. Click the column heading for the full story.
4. Next comes two more pieces of information about the lowest cloud: the height of its base in hundreds of metres and the direction it is moving from. So 3/SW means a cloud base of 300m (1000 feet) and the cloud's moving from the southwest, and 15/NE is 1,500m or 1.5km from the northeast. When the cloud base is 300m or lower, it turns a dirty shade of grey. Cumulonimbus (storm clouds) are colour coded: and
5. Next is the predominant type of middle level cloud. There are some exotic beasts here, the most useful of which is altocumulus castellanus, a remarkably accurate harbinger of thunderstorms.
6. Finally comes the predominant type of high cloud and what it's doing. As with middle level cloud, there are nine types and nine symbols.

The direction is given in degrees from north and the speed in km/h. So:
090/15 = easterly at 15km/h (i.e. the wind is blowing from the east)
180/45 = southerly 45km/h
270/30 = westerly 30km/h
360/02 = northerly at 2km/h (north is 360° not 0° so that it won't confuse with 0/0 which is, of course, Calm.

The wind cell is colour coded to highlight standard wind strengths according to the Beaufort Scale:

Why use degrees instead of the more common N, NNE, NE etc? Simply because 36 separations of measurement give more accuracy than 16, and allow you to see more clearly any gradual backing or veering of the wind.

The standard air temperature measurement of a dry thermometer bulb exposed in a Stevenson Screen.

The dew point temperature is a standard measure of humidity. It is the temperature to which you would have to cool the air to make it fully saturated.

A more popular, but less accurate, measure of humidity. It's the percentage of the amount of moisture present in the air at the present temperature relative to the amount that would be present if the air were saturated.

Three pieces of information:
1. The barometer reading in hectopascals (hPa), aka millibars, converted to sea level.
2. The observer's interpretation of the shape of the barograph (recording barometer) trace on the chart over the past 3 hours.
3. The change, in hPa over the past 3 hours.
So, 3.4 = falling steadily by 3.4hPa over the past 3 hours, and
2.4 = falling then rising a bit, but overall a fall of 2.4hPa over the past 3 hours. All the symbols are shown here.

There is a huge amount of information in these three symbols, which are pretty easy to understand. Click here for present weather symbols, and here for past weather symbols to get full details. You can also click on the column headings in the report. However, the important symbols (about 90% of them) are colour coded with this simple colour scheme:

	Light green for light rain or showers, moderate green for moderate, dark green for heavy.
	Yellow for lightning or thunderstorms, red for present thunderstorms with hail, severe storms and tornadoes or waterspouts.
	Light mauve for hail, dark mauve if it's heavy and associated with thunderstorms
	Light blue for snow, sleet, freezing fog or rain, or any solid precipitation or blowing snow; dark blue if it's heavy
	Tan for dust in the air, dust storms, dust devils
	A murky grey for fog
	Purple for wind squalls

All up, there are 99 symbols for present weather (the weather at the time or shortly before the observation), and 9 symbols for past weather (since the last observation). What's more, the observer can use two symbols for past weather to give a more complete picture. So past weather symbols of tell us that there's been a thunderstorm, with cloud varying above and below half cover since the last observation.

The present weather symbols convey many subtle shades of meaning. For example:
= dust in the air, but not raised locally by the wind
= dust, sand (or sea spray -- that's the loopy symbol) raised locally by the wind
= dust devils (willy willies) raising dust
= a dust or sand storm within sight but not at the station
and then there are 6 symbols for full-on dust storms, culminating in , severe dust storm increasing!
Add to this 14 types of fog, 17 types of rain (not including showers), and numerous permutations of thunderstorms, hail, tornadoes, squalls, ice needles and pellets, snow grains and crystals, and you have a Chamber of Weather Horrors capable of covering every eventuality.

Visibility. The greatest distance at which clearly defined objects (e.g. power transmission masts) can be identified. This is given in kilometres and tenths. Colour coding is used to show progressive levels of murk:

This contains any plain text message sent in by the observer with the obs. Some are quite chatty, and there is often additional information here about notable weather events. There's also the odd mention of broken thermometers, missing supplies, errors in earlier observations and other administrative trivia. AWSs are less chatty, but do send in their rainfall for the hour leading up to the observation thus: HR006=6mm.

What are the criteria for reports in the National Severe Weather Report?

Saving reports to your computer

If you want to save 3 hourly synoptic reports or daily data for the month reports to your hard disk for later reference, you need to take a moment to set up your computer to display them correctly. The report files use a style sheet and over 100 small gif image files to display in the format you see on the internet, and you need to recreate this environment on your computer. It's easy -- follow these steps (for Windows):

1. Download this zip file by right-clicking the link and saving it to the root directory of your main drive (probably C:\)
2. Using My Computer or Windows Explorer, locate the file AWN_Reports.zip and unzip it into the C:\ root folder or any folder of your choice. Be sure you have "use folder names" or equivalent selected so that the correct folder structure will be created.
3. You should now find a new folder called AWN_Reports has been created. Under it are three subfolders. Leave the fonts and styles folders alone.
4. Save reports to the reports subfolder. The synoptic reports use frames for presentation, so you need to open the report in a window of its own. This is best done by following the Map select or archives link, right clicking the report you want to save and selecting open in new window, then saving the file (also see the first troubleshooting note below).
5. Now, when you open the reports, you will find that they work the same as they do on the Web. If you want to use multiple folders to sort the reports, create them on the same level as the reports subfolder, or the fonts and style sheet will not link to them properly.
6. Use the Feedback link above to let me know of any problems you have.

Troubleshooting notes:

• If you are using Internet Explorer, open the page you want to save, click File > Save As then in the Save as Type box select Web Page, HTML only. Give the file a name (I use something like yearmodaID.htm, e.g. 20030405SydneyObs.htm) and click Save. If you use the default Save as Type box, IE will save all the associated gif and style files into a special subdirectory each time you save a file, and these subdirectories use a lot of unnecessary diskspace.
• If you open a file and find that some of the symbols are missing, hit reload a few times. I have had this happen with Internet Explorer but not yet with Opera or Netscape. Once the symbols are read into the browser cache, you shouldn't have any further problems in the same session.