Experiments in Numerical Objective Frontal Analysis1

A major area of weather analysis still requiring manual subjective determination is that of locating fronts. The experiments reported on here concern an attempt to incorporate objective frontal analysis into the operational computer routines of the U.S. Navy Fleet Numerical Weather Facility, Monterey, Calif. The synoptically-important numerically-derived frontal zone is regarded as a hyperbaroclinic region whose boundaries may be defined as quasi first-order thermal and moisture discontinuities; the boundaries are located through use of suitably defined second derivatives of various potential temperature parameters. Application is made to 850-mb. and surface (or 1000-mb.) frontal analyses on a hemispheric basis. The analyses for 0000 and 1200 gmt January 1, 1965 are selected to exemplify results of the most promising of the experiments. Verification against hand-derived frontal analyses, difficulties with the existing scheme, and proposed modifications to the continuing program are discussed.