AIR MAIL
Where today’s air came from
The air arriving over Decatur about 5,000 feet above the ground was over the western Atlantic three days ago, and over New England a day ago, about 1,020 miles back along its path. The nine paths traced from around the city fan out, so treat that as a best guess. It came down from about 13,200 feet up, warming and drying as it sank. Near the ground the air came from a point about 670 miles to the northeast; at 10,000 feet, from the Atlantic off the Carolinas. Traced back 72 hours through NOAA’s hourly RAP analyses and the GFS beyond them, nine paths at each of three heights.