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: Relative Humidity at 925 hPa Description: This chart shows the relative humidity at 925 hPa, which is equivalent to an altitude of about 2100 to 2500 ft a.s.l. depending on the SLP. With the help of this map one is able to draw conclusions on the portion of the sky cover formed by low-level stratocumulus clouds. Stratocumulus cover is particularly hard to forecast on the backside of a trough. Therefore the 'RH 925 hPa' is an essential supplementation to the 'RH 700 hPa' map.