What is the significance of 45°W in Meteorology? Or is there any significance at all. This is a question about numerical weather prediction. In particular weather forecast/prediction maps. I've noticed on some there is a demarcation at this point on some maps. The imaginary line cuts down the center of Greenland. It is possible it's just for calculation on the GIS. I wondered if anybody had a definitive answer. The map is flat for display purposes not spherical.