Hourly Gulf Stream Position, Width, and Orientation Estimates with HF Radar off Cape Hatteras, North Carolina, U.S.A.

Hourly time series of the landward edge of the Gulf Stream (GS), width of the cyclonic shear zone, and the orientation of the GS have been formed by first identifying the maxima in a single radar's radial surface current shears and current speeds. Maxima are chosen from within areas of consistent radar measurements over the time period sampled. Four bearings are selected for analysis, two where the GS enters and two where it exits the radar coverage. The width of the cyclonic shear zone is measured as the distance between the maximum in the gradient of the radial current speed, and the maximum in the speed along a single bearing. The orientation of the current is estimated by comparing the location of these maxima between the four selected bearings. This method is applied to two separate 5MHz Seasonde radars that consistently make GS measurements along the NC coast. The method benefits from recent application of radial metric quality controls on radial surface currents in the NC radar network that improves radial and total surface currents. The efficacy of the method is evaluated by comparing these estimates to those made using total surface currents from the radar network, satellite sea surface temperatures, and satellite altimetry. The radar hourly surface current measurements are more frequent than satellite observations and are not inhibited by cloud cover. Consistent long-term GS position estimates are expected to provide valuable new insights about the oceanography offshore of Cape Hatteras, NC.