Estimating Gulf Stream Position with HF Radar off Cape Hatteras NC

We present a method to measure the landward edge of the Gulf Stream, estimate the width of the cyclonic shear zone, and estimate the orientation of the Gulf Stream by 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 chosen, two where the Gulf Stream 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 three separate 5MHz Seasonde radars that have coverage along the NC coast. Comparisons between collocated radar estimates and those made bi-daily of Gulf Stream position by the Naval Oceanographic Office will be presented. The radar hourly surface currents measurements are more frequent than satellite SST (sea surface temperature) observations and are not inhibited by cloud cover. Consistent long-term Gulf Stream position estimates are expected to provide valuable new insights about the oceanography offshore of Cape Hatteras, NC.