The Atlantic pressure charts show the expected synoptic situation at lunchtime for the days shown. The white lines on the chart show areas of equal pressure and are known as isobars. The charts also show weather fronts and pressure centres marked as HIGH or LOW. The charts are generated automatically, but BBC Broadcast Meteorologists add the weather fronts (please note that the fronts for day five will be added when the data arrives, which is slightly later than for days one to four). For more information on pressure charts see our feature