Internet Weather Forecasting

all different

[BeeDeeDubbleU]

Is it just my area or is Internet weather forecasting drawn from a bag? Four day forecast for Glasgow, UK today ...

Yahoo
Sat Showers high 23
Sun Showers high 19
Mon Showers high 20
Tue Partly cloudy, high 23

BBC
Sat Sunny Intervals, High 24
Sun Sunny Intervals, High 21
Mon Light Showers High 23
Tue Sunny, High 20

Weather Channel
Sat Showers High 23
Sun Showers High 19
Mon Light Rain, High 20
Tue Partly cloudy, High 23

Weather Underground
Sat Scattered Clouds, High 25
Sun Chance of Rain, High, 21
Mon Clear, High 19
Tue Partly cloudy, High 19

UK Met Office
Sat Sunny Intervals, High 23
Sun Sunny Intervals, High 20
Mon Light Showers, High 23
Tue Sunny Intervals, High 22

Summary
On Saturday we will either have showers or sunny intervals. Temperature will be 23 or 24 or 25.

On Sunday we will either have showers or sunny intervals. Temperature will be either 19, 20 or 21 (or just 17 if you believe Excite).

On Monday we will either have showers or light rain. Temperature will be 19, 20 or 23.

On Tuesday it will either be sunny or cloudy. Temperature will be 19, 20, 22 or 23.

Then you go to Metcheck and get something else. Why are they all different?

[added]none of them forecast rain today but as I look out of my window guess what has just happened?[/added]

[edited by: BeeDeeDubbleU at 12:05 pm (utc) on July 21, 2006]

[zCat]

So you can pick the weather forecast you like best? Or maybe it's just a consquence of the unpredictable British weather...

[rocknbil]

So . . . you are just figuring out that forcasting the weather is as reliable as gazing upon a crystal ball? :-)

To directly answer the Q, it really depends on what actual service is used to collect the data and how often it is updated. Most raw US weather data, for example, initially comes from the NOAA [weather.noaa.gov]. The raw data is distributed free, but you are asked only to grab it once an hour.

As I recall the data itself is updated hourly (or is it every 15 minutes . . . ), but often it fails. When this happens, the one grabbing the data gets old data. Most of this data is collected via various weather stations, some of which are reported manually - anyone who has a barometer, thermometer, and other methods of collecting weather data can volunteer to report conditions in an area that has no method of collection. So in some cases, some "data collection stations" are no more than a hayseed farmer looking out his door and hollering "looks like rain Martha . . ." :-)

It gets better. Say you have a military installation with accurate equipment at 5000 feet, another one at a municipal airport 20 miles away at 3000 feet, and in between is Anytown, USA at 2000 feet with no data reporting. So how do you get ACCURATE weather for Anytown, USA? The answer is to triangulate the weather from all avaialble points and come to a best guess. Which is often miles off.

How do I know this? "We want weather on our site-" a site that serves 27 cities, and I was charged with doing so (using only free resources, of course.) The company is located in Anytown USA, and consequently I get semi-daily reports of how far off the weather reports are.

That being said, weather.com appears to be the closest out of all of them.
There's the long answer. :-)

[BeeDeeDubbleU]

And backing up my case :)

[theregister.co.uk...]