Every 12 hours, the National Oceanic and Atmospheric Administration (NOAA) launches weather balloons from approximately 70 locations across the US. While these do provide valuable data, a lot can change between those intervals and those locations. That's why a new project is taking advantage of something that's already going up in the sky on a much more frequent basis and in a higher number of locations – Southwest Airlines jets.
Along with NOAA and Southwest, the other partners in the initiative are SpectraSensors and Aeronautical Radio Incorporated.
So far, 87 of the airline's Boeing 737s have been fitted with Water Vapor Sensing Systems (WVSS-II) made by SpectraSensors. These are the same sensors already used on balloons, to measure moisture distribution throughout the atmosphere. By observing how that distribution changes over time, aviation weather forecasters are able to make predictions regarding things like "location and timing of fog, cloud formation and dissipation, and altitudes of cloud ceilings."
The newly-deployed sensors will make measurements hundreds of times in one flight, as each aircraft ascends and descends through the atmosphere during take-off and landing. Readings will be automatically transmitted to the headquarters of Aeronautical Radio Incorporated, then processed and relayed to the US National Weather Service (part of NOAA) for use in weather forecasts and warnings.
Plans call for additional WVSS-II's to be added to more aircraft in Southwest's fleet. The project is part of NOAA's Weather Ready Nation initiative, which is aimed at "building community resilience in the face of extreme weather events."
More information is available in the video below.