Observations of wind stress direction during Typhoon Chaba (2010)

Direct flux measurements of stress direction taken at the ocean surface during Typhoon Chaba (2010) over 3 days are examined for wind speeds between 12 and 26.5 m s(-1). Results show stress deviated up to 35 degrees from the wind direction and resided predominantly between the wind and peak wave directions in both bimodal and unimodal seas. Off-wind stress angle was most pronounced in Chaba's wake where wind sea and swell created an apparent unimodal system with narrow directional spread. These conditions lasted 2 days during which the stress direction was midway between the wind and wave directions. The implications for tropical cyclone forecasting are discussed.