A case study of the space and time continuity of numerical frontal analysis.

Abstract

The space and time continuity of numerical fronts as operationally produced by the Fleet Numerical Weather Facility, Monterey, California (FNWF), are investigated at 1000, 850, 700, 500, and 300 mbs for the four-day period January 25-28, 1967. Front locations, intensities, movements and slopes are examined over North America and compared with those from other analysis centers. Vertical structures of baroclinic zones and their changes with time are also investigated. Finally, a study is made of the FNWF computer- processed temperature fields compared to manually analyzed temperatures. Results indicate reasonable vertical consistency of frontal information in the central and eastern United States below the 700-mb level. Time continuity is best maintained at the 700-mb surface. A fictitious displacement of numerical fronts toward the warm air is observed at each of the mandatory pressure levels considered. The temperature fields of FNWF are found to produce smoothing of thermal perturbations associated with open frontal waves while relaxing the thermal gradient which leads to widening and weakening of baroclinic zones.