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How should I use the forecast? (limitations)
The data used to produce the XCWeather forecast is from a high quality numerical weather prediction model run by the United States government (GFS). The output from this model gives forecast data in the form of a grid of points at ½ degree (50km) intervals. XCWeather then interpolates this information to give a forecast for each location. You should be aware that at this resolution the forecast will not be able to fully model topographical effects at the scales depicted. This means that in coastal areas localised effects such as sea breezes will not be fully incorporated into the prediction and that wind speeds in elevated areas will be given as if taken at a height of 10 meters above sea level. Also beware that the forecast gives average wind speed but you may well experience significantly higher gust speeds.
Please use this forecast information advisedly and utilise your knowledge of the area when making decisions.
For more information on interpreting numerical weather prediction information take a look at Frank Singleton's web pages. For the meteorologists out there GFS is not a mesoscale forecast.
Observation Information
Current weather information is taken from carefully calibrated instruments sited at each location and barring technical difficulties will accurately reflect the conditions at the time of the observation. Wind speed measurements are made at a height of 10 meters.
The maps are updated every 30 minutes. Please note that the time stamp on the map is when the image was created which will not necessarily be the same time as the observations were taken. The actual time of each observation is clearly noted below the station name. If the observation is over 3 hours old the map arrow will be grey and the time stamp will be in red. Observations over 5 hours old are removed from the map.
How do I print the forecast?
To print the forecast for a given location, place your mouse pointer over the required station and then whilst the forecast is displayed press the ctrl and p keys.
What's the 'temp - dew' map all about?
The map labelled 'Temp - Dew' gives the difference in degrees C between the current temperature and dew point. This might seem like an odd value to plot but thanks to Tom Bradbury's useful rule of thumb, we can use this value to estimate the current cloudbase. Bradburys Rule states that "While the temperature is rising each degree C between the air temperature and the dew point is equivalent to about 400ft in the base of convective cloud. For example a difference of 10C should give a cloudbase of 4000ft. This rule is not valid once the temperature starts to fall.".
Using this rule and the map key, you can see that the darker the map the lower the cloudbase will be.
Station X has disappeared from the maps is there a problem?
All of the data plotted by XCWeather is obtained from free sources on the internet and sometimes this data is temporarily unavailable. This maybe because of problems on the internet itself (web servers crashing, internet connections going down) or because of equipment problems at the station.
In addition to transient problems, some stations are only manned during office hours so they disappear overnight and at weekends. Others are just notoriously fickle and only seem to submit reports when they feel like it (Blackpool and Cosford are two examples in this category).
In any event XCWeather will keep looking for the data every half an hour and automatically start plotting it as soon as it's available. Unfortunately it's rare that I can do anything to speed up this process.
Can you add a new arrow for location X?
I currently plot all of the freely available data that I've managed to find on the Internet so if your location is not already on the maps then I don't have a source of weather observations for the location and unfortunately I can't plot it.
However if you know of a source of free, reliable and accurate weather reports for a location that I don't currently plot then by all means let me know and I'll do my best to add it in. If the source of data is a privately owned weather station then please approach the station webmaster first and see if they are prepared to provide a free feed to XCWeather, then point them at this FAQ for further information.
If all else fails go buy yourself a weather station, stick it on your roof and start sending in your own observations.
Can I send data from my weather station to XCWeather?
If you own an internet linked weather station and would be happy to send a free data feed to XCWeather then drop me an email and let me know. I can't offer payment but you will be credited as the source of the data.
Ideally new stations should be in locations that currently have poor coverage on XCWeather. The sensors will need to be well sited (above the roof line and not in any wind shadow) and accurately calibrated.
The software you use will need to be able to send the observations via email in METAR format.
What was the wind strength at location X last Thursday night?
Unfortunately I don't keep any historical records so I can't help with this kind of enquiry.
However you could try
Weather Underground who do keep some historical data.
Look at the size of that arrow! That's never right!
I try to filter out as much erroneous data as possible but because XCWeather is totally automated it can be quite hard to catch all eventualities. Sometimes the problem is a miss-calibrated sensor at one of the stations or else it might be a genuine mistake on the part of the observer who's submitting the reports. In any event the problems are almost always transient and correct themselves in an hour or two. If a station consistently miss-reports let me know and I'll remove it from the map until it's fixed.
What do you do with any donations?
All of the donations to XCWeather go directly to paying the hosting bills and buying the computer kit. If you'd like to know a bit more about helping to keep the site up and running please click on the donate button.
Do you mind if I put a link from my site to XCWeather?
Please be my guest, the more the merrier.
Is it possible to link directly to the French page?
Est-il possible de lier directement à la page française?
Mais oui:
http://www.xcweather.co.uk?Loc=FR
What does XC stand for?
XC is an abbreviation for Cross-Country. If a paraglider pilot leaves the area they took off from and goes 'over the back' this is known as a cross-country flight.
Can I use your images and data on my website?
Please don't take the images or data from XCWeather.
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