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Cobbled Turbulence. Besides keeping tab on the jet stream, the Weather Bureau's new service will chart the ever-changing altitude of the tropopause, the varying boundary around 30,000 ft. between the troposphere (lower atmosphere) where the temperature generally decreases with altitude, and the stratosphere above it, where the temperature remains relatively constant.
The tropopause is a tough neighborhood, where violent winds jostle each other, break into swirls and eddies or porpoise up and down. This churning air (one kind is called "cobblestone turbulence") is often clear of clouds and therefore invisible, but it can seriously shake up a jetliner that slams through it unwarned at 690 m.p.h. Guided by the new Weather Bureau forecasts, a pilot can fly under, over or around the bumps, keeping the gravy off his passengers' clothes.