AIR MAIL
Where today’s air came from
The air arriving over Northfield about 5,000 feet above the ground was over the Atlantic off the Carolinas three days ago, and over New England a day ago, about 1,480 miles back along its path. It came down from about 9,500 feet up, warming and drying as it sank. Near the ground the air came from the North Atlantic; at 10,000 feet, from the western Atlantic. Traced back 72 hours through NOAA’s hourly RAP analyses and the GFS beyond them, nine paths at each of three heights.