As the category 4 storm makes landfall in Florida, it’s also making more land.
Hurricane Irma is already striking Miami and causing major damage, and Floridians further north who have not already evacuated are being urged to take cover. If anyone still needs convincing of how strong the storm is, here’s one mind-boggling indicator: As it moves, it’s dramatically shifting coastal ocean levels.
The first round of images showing this “draining” effect emerged as Irma closed in on the Bahamas.
After the hurricane moved north, the ocean returned.
Get Data Sheet, Fortune’s technology newsletter.
This afternoon, the same phenomenon is repeating itself further north. Images from a reporter with the Tampa Bay Times show that Tampa Bay, which normally lies between the cities of Tampa and St. Petersburg, has also been dramatically drained. Irma is expected to arrive in Tampa Bay late Sunday.
According to a meteorologist with Fox’s Tampa Bay affiliate, the dropping ocean levels are caused by strong winds.
Additionally, according to a meteorologist writing in The Washington Post, low pressure at the center of a hurricane can literally vacuum water into a “bulge,” lowering surrounding water levels.
While it’s clearly tempting to venture out on the bare seabed as the storm approaches, it’s not advisable, since water can return quickly and without warning.