Based on various runs of the GFS (Global Forecast System) from the NOAA in the USA, the ensembles show various possibilities of what might happen to the weather over the next two weeks.
The top lines (and the left-hand scale) indicate temperature, the bottom lines (and the right-hand scale) precipitation. The red temperature line indicates the average for the time of year and the thick green line the main "operational" run.
The ensembles should be taken as a general indicator of trends, rather than a definitive forecast of whether it's going to rain on your parade next Tuesday afternoon. The more agreement between runs (ie the closer the lines) the more likely the forecast is to be correct, though of course the runs can all be wrong.
Note that the temperature is at 850 hPa thickness - most easily understood as the air up in the sky rather than at ground level. Ground level temperatures are typically 5-10C higher.
The GFS ensembles are updated 4 times a day, from midnight, 0600, 1200 and 1800 GMT.
The "operational" run, of the GFS (Global Forecast System) from the NOAA in the USA, as described in the ensembles section. This app includes daily charts out to two weeks, again showing atmospheric thickness and temperature.
The GFS model is updated 4 times a day, from 0330, 0930, 1530 and 2130 GMT.
The forecast model from the European Centre for Medium-Range Weather Forecasts is one of Europe's most respected. Funded by 31 European states, the organisation is based in Reading. The charts in this app show pressure and 500 hPa thicknesses as forecast for the next 10 days.
The ECM charts are updated twice a day: at 1000 and 2300 GMT
The ECM ensembles are in a different format to the GFS ones, giving the predictions of various runs on ground temperature, dewpoint, precipitation, wind, gusts and cloud cover in separate graphs. The first two graphs are for temperature and cumulative precipitation on the ground in London. On these the overlaid blue line represents the GFS model (called the NCEP here). The subsequent forecasts are for the Netherlands, but are still useful as a guide to trends and forecast confidence.
Uniquely among charts in this app, these are created by human beings, at the UK Met Office. Though heavily informed by computer models, meteorologists can also use their judgement and override the automatically generated output to produce these predictions. Different charts are updated at different points through the day.
This app was created by Julius Honnor using weather charts from www.wetterzentrale.de and jQTouch, a jQuery plugin for mobile web development on the iPhone.
© www.juliushonnor.com 2010
The charts in this app are mostly from www.wetterzentrale.de, a German site that has an enormous selection of charts.
www.theweatheroutlook.com hosts an enthusiastic forum, mostly taken up with people discussing the latest model outlook, especially if there is cold weather in the offing.
Somewhat calmer, uk.sci.weather is the original UK web discussion group.
One of the most useful weather resources on the web is Darren Prescott's daily model interpretation, a well informed assessment of the current output of all the models. Darren posts this to both of the above groups early every morning.
Many areas cold, with a continued risk of ice.
Another sharp frost, with a risk of freezing fog, especially in the east. Showery rain and perhaps some snow will move southeastwards across northwest, central and southern England, heightening the ice risk here. Damp, but less cold in the west.
Low cloud and freezing fog will be slow to clear, but Scotland and northern England should see some sunshine. Remaining grey and damp across many southern areas. Generally staying cold.
Updated: 1514 on Sun 5 Feb 2012
Many areas cold with some sunshine by day, but a continued risk of sharp overnight frosts and freezing fog. Less cold in the northwest, with rain and snow at times.
Updated: 1514 on Sun 5 Feb 2012
"A northwest-southeast split is likely across the UK for much of the period through to mid-February. Southern, central and eastern areas should be largely dry and bright, but often cold or very cold with hard overnight frosts and some freezing fog patches. Further north and west conditions should be often less cold but windier, with bands of rain becoming slow-moving, giving snow on their forward edge and more generally over higher ground. Into the second weekend there are some signs that unsettled conditions further northwest could extend further south and east with a risk of more widespread snow, most likely across central and eastern areas of the UK, but confidence does remain quite low at this stage in the southeastward extent of any wintry weather.
Updated: 1150 on Sun 5 Feb 2012
"Though starting off cold, mainly across southeastern Britain, there looks to be a gradual trend to less cold and more changeable conditions in many areas, with temperatures by day and night closer to average. That said, being late February/early March, there is still a risk of overnight frost, especially through any quieter interludes. Further snow cannot be ruled out during any transition to milder conditions. By the end of the period however, rainfall, especially across southern areas looks to be above average. Sunshine amounts also look to remain around normal.
Updated: 1158 on Sun 5 Feb 2012
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