More details at the UK RASP site.
RASP for today
Output for Aston Down (AST) for Wednesday
The following graphs details the RASP atmospheric predictions for the date shown. This RASP forecast is for the Aston Down BGA turn point location.
For Cu Potential, a positive number means there will be Cumulus clouds, a good day is typically around a 1000 (or more).
On a good day, we need a 10 degree (or more) difference between the dry temperature and dew point.
A sun percentage value of 60% or more means that the ground will warm up and clouds can develop.
Less than 50% means there may be top cover or just too much cloud about (e.g. stratus "spread out" or Cirrus "top cover").
Ideally we do not want rain. A hint of a tenth of a millimetre means the air is fairly damp and the wet/dry temperatures will be close to each other.
The 'Stars' Forecast is experimental and based on original work by Paul Scorer.
Compare sun reaching the surface (%) to boundary layer cloud cover. If boundary layer cover is close to zero, surface sun is usually 85% or higher. If less than 85% there is top cover.