Powerful Hurricane Erin has undergone a period of astonishingly rapid intensification — a phenomenon that has become far more common in recent years as the planet warms. It was a rare Category 5 for a time Saturday before becoming a Category 4,

The National Hurricane Center is tracking two systems in the Atlantic basin, including Invest 98L, which could become a tropical depression before moving onshore in either Mexico or southern Texas.

Hurricane Erin was downgraded to a Category 3 hurricane early Sunday as a tropical storm warning was issued for the Turks and Caicos Islands and winds and heavy rains whipped the Virgin Islands and Puerto Rico.

As of Saturday evening, Hurricane Erin had weakened into a Category 4 storm with maximum sustained winds of 150 mph, the National Hurricane Center said. The National Oceanic and Atmospheric Administration and Air Force Hurricane Hunter Aircraft suggested that Erin is undergoing an eyewall replacement cycle,