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: Mean relative humidity between ca. 3000 and 6000 m above the ground Description: This map presents the mean relative humidity between about 3000 and 6000m a.s.l. - equivalent to the atmospheric layer between 10,000 and 20,000 ft. This is the atmospheric region where middle and high stratus clouds form. They are typically fringing a warm ridge along the anticyclonic sector of a frontal zone. In general, middle and high stratus clouds are a good indicator for the run of the jet stream. Mean Relative Humidity in the layer between about 600 and 3000 m above ground