"It's hard to really know what's going on deep down inside the bowels of a storm", he said, and whether that drop in pressure is causing the inner or outer winds of the storm to intensify.
Officials adjusted the evacuation plan for Irma as forecasts shifted the storm's predicted path further westward.
At its peak, the National Hurricane Center said the storm had maximum sustained winds of 130 miles per hour. On Sunday, Irma claimed its first United States fatality - a man found dead in a pickup truck that had crashed into a tree in high winds in the town of Marathon, in the Keys.
US President Donald Trump has signed a $15 billion hurricane relief package as the National Hurricane Center announced the imminent arrival of a monstrous storm forcing millions of Americans from the southern states of Florida and Georgia to evacuate.
From there, Irma is expected to push into Alabama, Mississippi and Tennessee on Tuesday and Wednesday.
A Key West, Florida woman fled to Miami, where she gave birth right before Hurricane Irma started to hit Florida over the weekend.
Irma, which prompted one of the largest evacuations in USA history, was a Category 4 hurricane about 20 miles (30 km) east-southeast of Key West, Florida, as of 8 a.m. EDT (1200 GMT), the NHC reported.
Irma's rampage across Florida broke records in Jacksonville before heading north to torment Georgia and beyond.
- Strong winds and flash flooding are still a threat as Irma spins into north Florida and toward Georgia over the next 24 hours.
Tropical storm warnings were are in effect for the Lowcountry of SC.
It was downgraded to a tropical storm Monday morning.
It killed at least 26 people before leaving the Caribbean for Florida.
Hurricane Irma continued today to destroy vast areas in Florida.
People in the heavily populated Tampa-St Petersburg area were braced for its first direct hit from a major hurricane since 1921.
Everybody FPL has is "already being deployed" and the company is working to secure more workers from out of state to help, Silagy said, including some crews who were assisting in Texas after Hurricane Harvey.