Model: Local weather forecast model from the UK MetOffice Update: 4 times per day, from 00:00, 05:00, 11:00 und 17:00 GMT Greenwich Mean Time: 12:00 GMT = 13:00 BST Variable: Geopotential Height and Temperature at 850 hPa Description: This chart helps to identify areas of densely packed isotherms (lines of equal temperature) indicating a front. Aside from this you can use the modeled temperature in 850 hPa (5000 ft a.s.l.) to make a rough estimate on the expected maximum temperature in 2m above the ground. However, this method does not apply to (winter) inversions.