Coastal Frontogenesis

Abstract

Detailed synoptic analyses are made of mesoscale frontogenesis situations along the southeastern New England coast. Temperature gradients of 5?10C over 5?10 km along a line separating light northerly or northwesterly flow from stronger easterly flow are common. The coastal thermal contrast may follow 6?12 hr after the establishment of a cold anticyclone to the north of New England and persist for 12 hr. Dissipation takes place when in offshore cyclonic circulation reaches the latitude of southern New England such that coastal winds back to northerly. The whole process is called coastal frontogenesis. A persistent tendency for coastal fronts to stagnate along a Boston to Providence line is noted. Precipitation appears to be enhanced along and just on the cold side of the frontal zone. Arguments are presented in favor of the importance of surface friction, orography, coastal configuration, and land-sea thermal contrast on the life cycle of coastal fronts. An inspection of eight years of data suggests that coastal frontogenesis is a maximum in late fall and early winter when land-sea temperature contrasts are greatest. Evidence is presented in one case of a coastal front, acting as a channel for a developing secondary wave disturbance, with latent heat release associated with the precipitation maximum proving to be important for development.