Web Caches

Sometimes your web browser may show old data in web pages. For example, if radar images are more than a day old, they are definitely out of date.

First try pressing refresh button in your browser ( Refresh button in Microsoft Internet Explorer and Reload button in Firefox, Mozilla and Opera).

If this gives you new data, then your web browser is probably OK, and you have just revisited a web page using your web browser's Back button. You just have to remember to press the Refresh/Reload button when you re-look at radar web pages you were looking at more than 10 minutes ago.

If the data is still not new, then it may be due to a lack of new data, e.g. that radar may have broken down, or may be busy for one and a half hours in windfinding mode.

Try an alternative radar, like any of the capital city radars which are all full-time and are not interrupted by windfinding duties. You will need to try over a period of about 30 minutes, to check that the timestamps you see in the first minute are changed after 15 or more minutes. The first set of images you see will have the right time, but if there is a problem then the time may not change after 15 minutes, even after you have pressed the refresh/reload button.

If the timestamps are never changing, over several radars, and after 15 minutes, then you may have a CACHE problem - either in your web browser cache, or (rarely) in your Internet Service Provider's cache.

Whats next in the Radar Loop Test

Web Browser Cache

This means that when you download a web page from a site, your web browser on your computer, unbeknownst to you, will keep a copy in its 'web browser cache' in a temporary directory somewhere. If you need to refer to that web page again, your browser can get it straight from the computer's disk (fast) rather than back over the Internet (slow).

The size of the cache is generally configurable by using the 'Options' button and then a subsequent option. You can set it to zero to stop caching and always go the the Internet (but normally you would not do this). The browsers perform house keeping to only keep a certain number of documents in the cache so they are not filling up your disk.

Caches are generally good as they do improve performance, especially for static documents (ie, ones not updated regularly). However, the one time that they aren't so good is for dynamic data like some of that available at the Bureau of Meteorology's site. If the browser thinks that it has a copy of a requested file in its cache, it may not go back to the Internet to get a new copy. It will just use the local copy. For highly dynamic data, this is bad and this causes old data to be shown instead of new data.

Technically, the browser can ask the server for the date of the last update of the requested document and use the local copy if it is the same age or download the document if it is newer. Most browsers do this properly but some browsers do not.

Suggested Solution:

If you feel a web page is old and is not updating when you do a normal refresh/reload, then do a forced-reload ( shift-refresh for Microsoft Internet Explorer and shift-reload for Netscape, Mozilla, Firefox) and you will force the browser to go to the Internet to get a fresh copy.

If you now see a fresh version of that page, you can assume that your web browser cache was causing the problem. Please check your browser cache settings to see if you can fix the problem.

If you are doing shift-refresh/reload and you still cannot get fresh versions of web pages, then you may have an Internet Service Provider Cache problem (see section below).

Clearing the Web Browser Cache

Especially with caches that are large in size and nearly full, the mechanics of fetching an image, finding room to insert it into the cache and then actually looping it within a fixed time can prove too much work for some browsers. In such a circumstance, the end result can be that only the 'please wait' message is displayed whilst fetching activity continues. A solution is to clear out the browser cache. This substantially reduces the work that the browser must do and gives it a chance to display the image. An unfortunate consequence of this is that all of the images and text must be fetched again, not only for the Bureau's radar site but for all sites (and that 'working offline' has nothing to display as it uses the entries in the cache) but it can clear problems such as not seeing the loop update at all.

Internet Service Provider Cache

In the same way that your web browser has a cache of recent web pages, your Internet Service Provider can use the same strategy and may be doing so on your behalf.

In some (rare) cases, even though you are using shift-refresh to get fresh web pages from the internet, the pages still seem to be old. This may be because your Internet Service Provider also has a cache and their cache may not be set up quite right, and they are not fetching fresh web pages themselves.

Suggested Solution:

This is a little harder to fix and you will have to liaise with your Service Provider carefully explaining the problem. He/she should then be able to fix it for you.

When all else fails

If you have been through the steps above, and you think your web browser cache settings are good, and you have checked with your Internet Service Provider and they say that they OK, then email us and we may be able to help with your problem. Use our FEEDBACK link to tell us your web browser name (Explorer, Firefox, Netscape, Opera or whatever) and version number, and the symptoms of your problem. Mention that you have used this 'Web Cache' page to try and track down your problem.