WX MODEL 15: Low Level Moisture


850 mb to 500 mb relative humidity can be used to assess how saturated the lower troposphere is. Values from 80 to 100% indicate near saturation of the air. This is important since lifting will quickly be able to condense precipitation from the air. High values of relative humidity are common in the places that lifting mechanisms are present, such as fronts and low pressure systems. The two basic ingredients for precipitation are saturated air and lifting. If 700 mb UVV is upwards at the same time the 850-500 mb relative humidity is 100%, then precipitation is likely.

The image below shows relative humidity. The highest relative humidity is the light blue shading that is off the east coast and over Florida. The lightest band is 90% and higher relative humidity. This is along a front. Higher relative humidities are also over Missouri. A shortwave is moving through this area causing rising air and air that is closer to saturation.