AIR MAIL
Where today’s air came from
The air arriving over Henry Clay about 5,000 feet above the ground was over the Atlantic off Florida three days ago, and over the Great Lakes a day ago, about 1,720 miles back along its path. It came down from about 10,300 feet up, warming and drying as it sank. Near the ground the air came from the western Atlantic; at 10,000 feet, from Quebec. Traced back 72 hours through NOAA’s hourly RAP analyses and the GFS beyond them, nine paths at each of three heights.