AIR MAIL
Where today’s air came from
The air arriving over Kratka about 5,000 feet above the ground was over southern California three days ago, and over the northern Plains a day ago, about 1,620 miles back along its path. It came down from about 9,300 feet up, warming and drying as it sank. Near the ground the air came from a point about 980 miles to the south; at 10,000 feet, from southern California. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.