Mesoscale Wind Signatures along the Carolina Coast

Abstract

Coastal winds immediately offshore of North and South Carolina often exhibit a mesoscale diffluent?confluent pattern that appears to be governed by the coastal configuration and oceanic thermal field. The stationary pattern roughly parallels the coastline within 50 km of shore during winter when synoptic-scale conditions support northerly winds. Data obtained during the Genesis of Atlantic Lows Experiment (GALE) are statistically analyzed to document the surface winds in this offshore zone. Several specific examples of the mesoscale pattern are presented and compared with results from a simple theoretical model with diabatic heating. For an inviscid flow over an isolated bell-shaped heat source, the air parcels rise in the vicinity of the heating region and descend on both the upstream and downstream sides. A confluent zone is produced in the vicinity of the heat source. With an idealized heat source resembling the observed pattern of sensible heat flux, the flow pattern is similar to that observed. Frictional effects are shown to be negligible. Thus, results from the simple theoretical model suggest that diabatic heating is largely responsible for the observed flow pattern.