def to_wea(self, file_path, hoys=None):
        """Write an wea file from the epw file.

        WEA carries radiation values from epw. Gendaymtx uses these values to
        generate the sky. For an annual analysis it is identical to using epw2wea.

        args:
            file_path: Full file path for output file.
            hoys: List of hours of the year. Default is 0-8759.
        """
        hoys = hoys or xrange(len(self.direct_normal_radiation.datetimes))
        if not file_path.lower().endswith('.wea'):
            file_path += '.wea'

        originally_ip = False
        if self.is_ip is True:
            self.convert_to_si()
            originally_ip = True

        # write header
        lines = [self._get_wea_header()]
        # write values
        datetimes = self.direct_normal_radiation.datetimes
        for hoy in hoys:
            dir_rad = self.direct_normal_radiation[hoy]
            dif_rad = self.diffuse_horizontal_radiation[hoy]
            line = "%d %d %.3f %d %d\n" \
                % (datetimes[hoy].month,
                   datetimes[hoy].day,
                   datetimes[hoy].hour + 0.5,
                   dir_rad, dif_rad)
            lines.append(line)

        file_data = ''.join(lines)
        write_to_file(file_path, file_data, True)

        if originally_ip is True:
            self.convert_to_ip()

        return file_path
Write an wea file from the epw file.

        WEA carries radiation values from epw. Gendaymtx uses these values to
        generate the sky. For an annual analysis it is identical to using epw2wea.

        args:
            file_path: Full file path for output file.
            hoys: List of hours of the year. Default is 0-8759.