Nick Underwood of NOAA flew through the eyewall to the calm center of Hurricane Dorian.
He estimates the quiet middle of the storm is 40 miles across.
On Twitter, he notes that the storm maintains an "incredible stadium effect eye" - that the eye of the storm is like being in the middle of a huge sports arena, with the clouds as seating.
Deserted, rain-lashed streets in Charleston, South Carolina, vanished beneath water on Thursday as Hurricane Dorian churned a few dozen miles offshore after reducing parts of the Bahamas to rubble.
Water pooled a few inches deep near the centuries-old waterfront.
In certain low-lying blocks, it rose to a foot or more, as high tide approached and forecasters warned of storm surges of up to 8 feet (2 meters).
John Rivers, 74, and his three children were among the few to be seen in the streets on Thursday.
They cleared drains of branches, leaves and debris, using a shovel, a rake and their bare hands.
"We're giving the water somewhere to go," Rivers said, sheltering temporarily from the driving rain and gusts of wind under a covered walkway.
His daughter Caroline, 12, pulled off her rubber boots one at a time, emptying a stream of water from each.
"I see this as a good life lesson for my kids," Rivers said.
Officials said Thursday afternoon that more than 7 inches (18 cm) of rain had fallen in parts of Charleston.
Dorian was about 50 miles (80 kilometers) off Charleston on Thursday, wavering in strength between a Category 2 and 3 on the five-step Saffir-Simpson wind scale.
It was forecast to possibly make landfall in North Carolina late Thursday or early Friday.
Life-threatening storm surges and dangerous winds were possible in much of the coast of South Carolina, North Carolina and Virginia, the National Weather Service said.