5640 Line at 5000 hPa (mb)

[mrandall]

Please consider adding a bolded line at 5640 meter geopotential height on the 5000 hPa (mb) charts. This line is important for marine navigation and weather routing because most storms track 300 to 600 nautical miles north or south (towards the poles) of this line. See: https://vos.noaa.gov/MWL/dec_08/milibar_chart.shtml