AIR MAIL
Where today’s air came from
The air arriving over Milan about 5,000 feet above the ground was over the Atlantic off the Carolinas three days ago, and over the western Atlantic a day ago, about 1,310 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 9,000 feet up, warming and drying as it sank. Near the ground the air came from the North Atlantic; at 10,000 feet, from a point about 300 miles to the southwest. Traced back 72 hours through NOAA’s hourly RAP analyses and the GFS beyond them, nine paths at each of three heights.