AIR MAIL
Where today’s air came from
The air arriving over Washington about 5,000 feet above the ground was over the Maritimes three days ago, and over New England a day ago, about 1,100 miles back along its path. Most of the nine paths traced from around the city agree. It came down from about 11,900 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.