During the winter you can do up to around 150mph in the jet stream.
There is an amateur radio ballooning group (CA Near Space Project) that sent up a balloon that went from CA to Algeria, 6,236 miles, in 57 hours for an average of 109mph. It doubled the previous record of 3,361 miles.
News article.
http://www.popsci.com/technology/article/2011-12/amateur-radio-balloon-makes-record-transcontinental-transatlantic-flight
Original article from CNSP.
http://www.cnsp-inc.com/cnsp-11/
They also had a second balloon that made a trans-Atlantic flight and landed in Morocco.
http://www.cnsp-inc.com/cnsp-18/
Thanks! Didn’t know about that.
While the balloon w/GPS & transmitter is cool, I’m most impressed that independent receivers turned into the data acquisition system. Nice.