How are meteorologists able to determine jet stream locations and the actual speed of the stream?
The key way of measuring the jet stream is by sending aloft weather balloons from around the country. The balloons carry a package of instruments called a “radiosonde.” The instruments measure temperature, humidity and air pressure and radio data back to earth. Since balloons go with the wind, radio tracking of the balloon’s path and speed gives the wind speeds and directions at various altitudes. Weather balloons are launched around the world at about midnight and noon “Zulu” time. (Zulu time used to be called Greenwich Mean Time and is also known as coordinated universal time. Now, in addition to data from weather balloons, many airliners are equipped to automatically send back data on the air temperature and wind speed and direction. These “automated pilot reports” help fill in the gaps, both in time and space, between weather balloon launches. But, reports are limited to where airliners fly, which means no reports are available from lower altitudes far away from airports. Instrumen
