Forecasters are watching a new tropical system that may form behind Hurricane Erin, which is intensifying again Monday as it tracks off the U.S. coast.

After exploding in strength at a historic rate this weekend, Hurricane Erin is now a sprawling Category 4 storm churning in the Atlantic. The storm’s enormous footprint is becoming the biggest concern as it threatens to drive life-threatening rip currents and towering waves toward the eastern US coastline and Bermuda.

Erin is not forecast to hit the U.S. directly, but coastal areas along the Eastern Seaboard will feel its effects with dangerous high waves and rip currents over the next several days. "These rough ocean conditions will likely cause life-threatening surf and rip currents," the National Hurricane Center warned.

The storm will remain a major hurricane through the middle of the week, according to the National Hurricane Center.

Tropical Storm Erin is likely to become Hurricane Erin shortly. It's now tracking over ocean water that's in the low 80s, and the dry and dusty air that has had a stranglehold on the circulation is dissipating.