An operational planetary boundary layer model (Brown, 1974,1978, 1981) for determining surface winds and stress from free-stream flow has been modified for the marine layer by including surface roughness feedback, variable humidity and interfacial layer effects. The surface winds determined from synoptic-scale pressure and temperature fields are compared to surface measurements in GOASEX and JASIN. Abstract An operational planetary boundary layer model (Brown, 1974,1978, 1981) for determining surface winds and stress from free-stream flow has been modified for the marine layer by including surface roughness feedback, variable humidity and interfacial layer effects. The surface winds determined from synoptic-scale pressure and temperature fields are compared to surface measurements in GOASEX and JASIN.