def get_utm_string(west_lon: float) -> str:
    """ Returns PROJ4 string for UTM projection for a given zone, computed
    using the west (longitude) value

    Parameters:
    ----------
    west_lon : float
        Longitude for the western most point of the domain

    Returns:
    -------
    PROJ4 string for the UTM zone
    """

    datum = 'WGS84'
    ellps = 'WGS84'
    zone_number = int((west_lon + 180) / 6) + 1
    proj_string = (f'+proj=utm +zone={zone_number} +datum={datum} +units=m'
                   f'+no_defs +ellps={ellps} +towgs84=0,0,0')
    return proj_string