Applying Theory to Operational Forecasting and Nowcasting
Operationally, one can determine the cold pool/lowlevel shear relationship by calculating the ratio of the speed of the cold pool, “C”, (which is theoretically proportional to the strength of the cold pool circulation) divided by the value of the outflow linenormal lowlevel vertical wind shear, “∆U”, where “lowlevel wind shear” should be the shear over the approximate depth of the cold pool. The average depth of cold pools has been found to be on average 1.7 km. Although shear in the cold pool layer is most important in determining the depth and strength of lift along the outflow, shear over a deeper layer is also a contributor, albeit to a lesser degree. Thus, it would be best to use the 03 km shear instead of 02 km, for example. Since the 3 km AGL is right around the 700 mb level, computing the low level shear is quick and easy  Just subtract the surface or 1000 mb wind from the 700 mb wind. The speed of the advancing outflow can easily be determined by using the distance speed tool in AWIPS.
A C/∆U ratio of 1 represents the optimal state for deep lifting by the outflow/cold pool. Values less than 1 signify that the ambient shear stronger relative to the cold pool and values greater than 1 signify that the cold pool is stronger than the ambient shear. This ratio is not only significant for anticipating the degree of lifting along outflow, but it is also important in determining the strength and longevity of linear MCS’s, since one of the primary forces driving MCS’s is their welldeveloped cold pools.

