On September 29, the disturbance developed a closed low-level atmospheric circulation.

Unable to maintain a closed circulation, the final advisory was issued.

The second is a magnetic dipole, a closed circulation of electric current.

That day, ships in the region confirmed the presence of a closed circulation.

By May 21 a tropical depression developed after the system formed a closed mid-level circulation.

A reconnaissance flight into the system on June 22 did not indicate a closed circulation.

By the following day, there was evidence of a weak closed circulation off the south coast of Jamaica.

Over the next three days, the system tracked westward and slowly began to develop a closed circulation.

A magnetic dipole is a closed circulation of electric current.

By late on the 6th, a closed circulation formed.