Dew point depression, a measure of relative humidity , is represented by the color filled regions and the associated values are indicated by the color code located in the lower left corner of the forecast panel. Dew point depressions are given as the difference between the dew point temperatures and the actual temperatures. The lower the dew point depression, the more moist the air, which is vital for the development of clouds and precipitation. Advection of heat and moisture along the 850mb surface can be used to predict what will occur at the surface. Thermal advection can indicate forthcoming surface temperature changes , amplification of upper level troughs and ridges , and changes in pressure at the surface.
Moisture advection is useful for predicting areas of precipitation.
850 hghts, temps Terms for using data resources. Credits and Acknowledgments for WW2010.