Model: GFS (Global Forecast System) Global Model from the "National Centers for Environmental Prediction" (NCEP) Update: 4 times per day, from 3:30, 09:30, 15:30 und 21:30 GMT Greenwich Mean Time: 12:00 GMT = 13:00 BST Parameter: Dew-point at 2m across the British Isles in hPa/h Description: The dew-point is the temperature air would have to be cooled to in order for saturation to occur. The dew-point temperature assumes there is no change in air pressure or moisture content of the air. Dew-point does not change with temperature of the air; very much different from relative humidity. The dew-point can be used to forecast low temperatures. The low will rarely fall far below the observed dew-point value in the evening (unless a front brings in a different air mass). Once the temperature drops to the dew-point, latent heat must be released to the atmosphere for the condensation process to take effect. This addition of heat offsets some or all of further cooling.