AIR MAIL
Where today’s air came from
The air arriving over Walpole about 5,000 feet above the ground was over Quebec three days ago, and over the western Atlantic a day ago, about 1,640 miles back along its path. The nine paths traced from around the city fan out, so treat that as a best guess. Near the ground the air came from a point about 660 miles to the northeast; at 10,000 feet, from the western Atlantic. Traced back 72 hours through NOAA’s hourly RAP analyses and the GFS beyond them, nine paths at each of three heights.