Level of Uncertainty in HF Radar Observations and Predictions
Both the HF Radar observed and predicted surface currents have some amount of uncertainty in the accuracy of the values presented.
For the observed surface currents, although the precise amount of error is difficult to quantify, HF Radar data is generally expected to be accurate to within 10 cm/s of current speed and 10 degrees of current direction. It is important to note, that the presented values are spatial and time averages - so that they may not be representative of the currents of a specific point within a grid cell (particularly near shore) or of an instant in time during the observed hourly period.
Uncertainty in the accuracy of the predictions is much greater. For most locations the primary source of differences between the predicted and observed surface current will be wind forcing (though water density differences can also be important). Depending on local meteorological conditions the actual speed and direction of the surface current at a particular location can be dramatically different than predicted.