Dear Tom,
Some depictions of jet streams show them to be narrow, but other depictions show them to be wide. What is the real story?
—Barry Schultz, Milwaukee area
Dear Barry,
The fastest jet stream winds, which have speeds varying from 60 mph to 230 mph or higher in extreme cases, typically flow in bands ranging from 200 to 400 miles in width. Surrounding these "jet cores" may be channels of elevated wind speeds that can reach 400 to 500 miles across. The paths of jet streams shift continually and their strongest winds can occur at widely varying heights. They typically form from 8,000 to 55,000 feet aloft between air masses of strongly differing temperatures. Jet streams also undergo seasonal changes: strengthening and shifting south on the periphery of cold air masses in winter and weakening and shifting north in summer when air mass temperature differences are less sharp.
