Two storms are churning in the Atlantic, but only one is a threat to the U.S.

A pair of storms is vexing forecasters in a messy Atlantic, and one could make landfall on the U.S. coast as soon as Monday.

A pair of storms is vexing forecasters in a messy Atlantic, and one could make landfall on the U.S. coast as soon as Monday.

Two storms — Hurricane Humberto and a brewing disturbance called AL94, for now — are roughly 800 miles away from each other as of Friday morning.

Because the two storms are so close, they are subject to each other’s influence and a phenomenon called the Fujiwhara effect.

“It’s a very complex problem. It doesn’t happen that often to get two storms this close together — especially two strong ones,” said Andy Hazelton, a hurricane modeler and associate scientist at the Cooperative Institute for Marine and Atmospheric Studies at the University of Miami.

The Fujiwhara effect describes when two storms are rotating in the same direction close to each other around a shared midpoint. Sometimes, the weaker of the two storms is subsumed by the stronger storm or the two merge. Other times, the two storms orbit each other before spinning off on individual tracks.