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° 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. Key Points Observations show wind stress direction in typhoon impacted by wavefield Stress direction in typhoon is misaligned up to 35° from the wind direction Wind sea and swell behind typhoon lack separation in frequency and direction.