The antenna station outside the Base Safety Office for the Wet-Bulb Globe Temperature machine. The black device on the left is the actual wet-bulb that uses wind force, barometric pressure, humidity and other factors to determine the actual ambient temperature to the appropriate heat index flag is posted at the front gate of MCLB Barstow. - The antenna station outside the Base Safety Office for the Wet-Bulb Globe Temperature machine. The black device on the left is the actual wet-bulb that uses wind force, barometric pressure, humidity and other factors to determine the actual ambient temperature to the appropriate heat index flag is posted at the front gate of MCLB Barstow.