def write_manningsn(fid, node, value):
    """
    Write out a formated node value line to fid

    :type fid: :class:`file`
    :param fid: the file object to be written to
    :type node: int
    :param node: the node number
    :type value: float
    :param value: the nodal value
    :rtype: string
    :return: formatted string for a line in a ``fort.13`` formatted file

    """
    return fid.write('{:<8d} {:17.15g}\n'.format(int(node), value))