In order to more definitively examine whether a quantifiable relationship exists between the 6.7-μm radiometric patterns observed by the Nimbus 4 temperture humidity infrared radiometer (THIR) within cloud free areas and tropospheric dynamics, a 10-level diagnostic model was employed. The model was used to show the spatial and temporal relationships existing between radiometrically observed water vapor patterns and conventionally derived water vapor patterns in these clear areas. This specifically involved examining the upper and middle tropospheric water vapor budget and the associated circulation dynamics. A particular synoptic situation involving the evolution of a cloud free tongue associated with a trough located to the lee of the Rocky Mountains over the central United States was examined. The THIR observations over the trough extended from 0538 GMT on Aprl 30, 1976, to 1850 GMT on May 1, 1970, at approximately 12-hour intervals. The diagnostic analysis revealed that the increase of the 6.7-μm equivalent blackbody temperatures (TRR) over this cloud free area during the confluent stage of the trough was associated with upper tropospheric drying that was initially caused by the advection of subsidence-dried air from upstream and later augmented by subsidence. The 6.7-μm observation was not found to be significantly useful over that of the window channel where the TBB were less than 245¿K, i.e., generally cloudy regions. Therefore the applications of the 6.7-μm observation are seen, based on this study, to apply best for providing spatial detail in the location, extent, and movement of dynamic features occurring in cloud free areas.