The system intensified fairly quickly, going from a minimal tropical storm to hurricane status in a 24 hour period.
It became a minimal tropical storm before hitting central Japan on the night of August 4.
Abby rapidly weakened to a minimal tropical storm a few days thereafter.
By the morning of May 20, the system had weakened to a minimal tropical storm and turned due west.
The cyclone remained a minimal tropical storm for most of its lifetime.
Calvin then moved over cooler water and subsequently weakened to a minimal tropical storm.
It continued to weaken, and was only a minimal tropical storm by the afternoon of August 21.
It headed north and peaked as a minimal tropical storm on October 1.
The system briefly weakened to a minimal tropical storm before strengthening again.
It became a minimal tropical storm during this acceleration.