Super Typhoon Atsani was one of two powerful typhoons to spin across the Northwest Pacific Ocean in mid-August. Unlike its sister storm, Typhoon Goni, Atsani recurved out to sea southeast of Japan rather than making landfall anywhere.
The storm did attain super typhoon status, however, maxing out at sustained winds of at least 160 miles per hour, according to the Joint Typhoon Warning Center.
But the storm did not simply die as it got caught up in the midlatitude jet stream winds. Instead, it was transformed into a huge and powerful extratropical storm. What this means is that it went from a storm that had a warm core, with its center milder than the surrounding air, into a cold core system.
[video id=c5NHk4dzqWdjmVsTGiHphKEymxM7Oqpu]
To do so, it drew energy from the jet stream, which itself is powered by the contrast in air masses in the northern midlatitudes. The storm that resulted produced hurricane force winds and extremely high waves across the north central Pacific, and helped rearrange the jet stream far downstream, across Alaska and the rest of North America.
The meteorologists at the University of Wisconsin posted a high resolution animation of satellite imagery showing the storm's transformation.
The National Weather Service's Ocean Prediction Center also created an animation showing the process at work.
Super Typhoon Atsani is forecast to spawn one hell of a mid-latitude cyclone next week over the Northwest Pacific pic.twitter.com/cG9lD7Xwnl— Michael Ventrice (@MJVentrice) August 21, 2015
Typhoon Atsani was a classic case in which a recurving storm in the Northwest Pacific energizes the jet stream and results in a faster and wavier upper air flow, hence stormier conditions downstream. Recurving refers to a directional change in the path of the storm, in this case from an original bearing of west/northwest, to its current past of northeast.