def strip_data(df):
    """Remove unused columns from the data."""
    names = [' dwpf', ' relh', ' drct',
             ' sknt', ' p01i', ' alti', ' mslp', ' vsby', ' gust', ' skyc1',
             ' skyc2', ' skyc3', ' skyc4', ' skyl1', ' skyl2', ' skyl3',
             ' skyl4', ' presentwx', ' metar']
    for colname in names:
        del df[colname]
    return df