AIR MAIL
Where today’s air came from
The air arriving over Wallagrass 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 1,340 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 Canada; at 10,000 feet, from the Atlantic off Florida. Traced back 72 hours through NOAA’s hourly RAP analyses and the GFS beyond them, nine paths at each of three heights.