AIR MAIL
Where today’s air came from
The air arriving over Perry about 5,000 feet above the ground was over the Atlantic off the Carolinas three days ago, and over the Great Lakes a day ago, about 1,660 miles back along its path. It came down from about 8,900 feet up, warming and drying as it sank. Near the ground the air came from the Atlantic off the Carolinas; at 10,000 feet, from Canada. Traced back 72 hours through NOAA’s hourly RAP analyses and the GFS beyond them, nine paths at each of three heights.