Which websites would you trust most for weather forecasts? I was thinking of taking tomorrow off work to do some gardening but BBC says it may snow –

http://news.bbc.co.uk/weather/forecast/345?area=NN1

Where as Metcheck says it is still going to be a nice day –

http://www.metcheck.com/V40/UK/FREE/tomorrow.asp?zipcode=nn1

Or are they all just making it up as they go along?

This one 😀

Having looked at both forecasts, I don’t see too much of difference with them. At 0600 when the BBC is forecasting snow the metcheck one says the temp will be about -1C. So the only difference is that at 0600 the BBC is expecting there to be precipitation whereas Metcheck are forecasting 65% cloud and no precipitation.

I’ve got to be honest they both look pretty similar to me. Incidently what time were you thinking about start your gardening.

I still prefer the looking out the window forecast.

I still prefer the looking out the window forecast.

Isn’t that what weather forecasters do anyway 😉

All the websites that ask you to enter a postcode are shite. They compare the postcode with the nearest datapoint from a raw computer model…in Metchecks case with the american GFS model, in BBC’s case with a limited subset of the gridpoints from UK MetOffice computer model.

For a whole set of reasons these datapoints may not be representative of the conditions that can be expected in that postcode area. It’s a classic example of data being available, but the expertise to interpret that data not available.

A meteorologist would never consider one datapoint in isolation…he/she would look at all the datapoints for hundreds of miles around, comparing them with results at those same datapoints for the previous computer runs, and crucially comparing how the current (real) weather compares with what the computer thinks the weather is like …especially if there are differences upstream of where he may be interested in forecasting for.

Learn to forecast the weather yourself

Here’s some charts (based on all the UK Met Office Model gridpoints) for next few days

http://www.metbrief.com/EGRR.html

Tomorrows (midday) chart is

which shows a nice big wodge of fine settled high pressure across most of the UK.

For most of southern/central england it’ll be dry, but with a fair amount of cloud. There is a small risk of some cloud sheets becoming thick enough to give a few spots of rain/sleet especially around daybreak tomorrow….but no more than a few spots, and I wouldn’t let it stop you doing any weeding.

http://www.yr.no

One common reason for conflicting forecasts on different sites is the fact that they use different thresholds of probability to fill in the graphic. So one site might consider a 20% chance enough to put the snow symbol on, another a 50% chance.

So you get different symbols for the same weather.

Anyway – DON’T just stick your postcode in and expect an accurate forecast (as above). Either:

Watch or listen to the TV or radio forecasts
Use the doppler radar images for the past 12 or 24 hours or so
Read the synoptic charts

The sites I use depend if I want detailed wind data or not. If not (i.e. everyday use) I go to yr.no and if I want wind data I use Windguru or XCWeather

http://www.yr.no

We have a winner. I seem to remember something about a company that was contractually obliged to use the Met Office for their weather getting into trouble for ditching them in favour of yr.no