mgrib(grib_field_position = 1,
grib_input_file_name = "t850.grb")
mcont(contour_level_selection_type = "level_list",
contour_shade_colour_method = "calculate",
contour_shade_method = "area_fill",
contour_shade = "on",
contour_level_list = [-20.00, -10.00,...,20.00, 50.00],
contour_line_colour = "grey",
contour_shade_colour_direction = "clockwise",
contour_line_thickness = 2,
contour_highlight = "off",
contour_label = "off",
contour_shade_max_level_colour = "red",
legend = "on",
contour_shade_min_level_colour = "blue")