It was said:
“After successful passes over the South Island, the balloons had continued east. Two wound up in the waters off New Zealand’s coast, the payloads recovered by a waiting Googler at sea.”
So, that says to me .. that they let the balloon pass through the lower stratospheric winds that are blowing from the west to east .. right on up to the upper stratospheric winds that are blowing from the east to the west. When the balloon got to the west side of the country they opened a valve to release helium .. dropping it to the lower stratosphere & it then floated back across the country eastward.
Why didn’t it go back up? It floated out over the sea before winding up in the water
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