You can clear old GRIBs from the Offshore App.

For Windows go to File (top left) >Settings >General >Clear Data >Clear GRIBs

For Mac click PredictWind Offshore (top left) >Settings >General >Clear Data >Clear GRIBs

For iOS/Android go to Main Menu >Preferences >General >Clear Data >Clear GRIBs

The Clear Data function is a 'one off' action and will not repeat.

Please note: when you do a download into the Offshore App it automatically replaces old GRIB files, routes etc. so it is not necessary to clear data before each download. However it is good house keeping from time to time or as first step Troubleshooting when a GRIB map does not appear for a model.