The above animated chart illustrates the upper air temperatures (850hPAs) over Ireland and the UK between Monday 13 December 2010 and Wednesday 22 December 2010.
The animation is based on the latest output from the ECM weather model (c) Meteociel. Air temperatures late next week are expected to be close to freezing while there will be severe nighttime frosts.
850 hPa level is roughly at 1.5 km, usually above the atmospheric boundary layer. That means there is no diurnal temperature variation, and the underlying surface such as cool sea doesn't affect it's temperature. That is why 850 hpa temperature is used to distinguish air masses and thus to locate cold and warm fronts. MORE