AIR MAIL
Where today’s air came from
The air arriving over Chelsea about 5,000 feet above the ground was over the North Atlantic three days ago, and over the western Atlantic a day ago, about 1,180 miles back along its path. Most of the nine paths traced from around the city agree. It rose from near the ground on the way. Near the ground the air came from the North Atlantic; at 10,000 feet, from a point about 300 miles to the south. Traced back 72 hours through NOAA’s hourly RAP analyses and the GFS beyond them, nine paths at each of three heights.