Atlantic Charts - Airmass
Chart shows forecast pressure and airmass temperature every 6 hours for 10 days.
Pressure:Isobars, lines of equal atmospheric pressure, are drawn every 4hPa (hectopascals or millibars). Areas of High and Low pressure are indicated. The closer the spacing of the isobars, the stronger the wind.
Airmass: Chart depicts regions of warm and cold airmasses. The boundaries between the warmer and cooler airmasses where the colours change rapidly depict frontal zones. The temperatures are not surface air temperatures and should not be taken as a forecast of temperature.