A storm surge is the abnormal rise in water levels during a storm when strong hurricane winds push a ball of water toward the shore as depths decrease. While winds are the primary cause of storm surges, they are also influenced by a storm’s approach angle, the shape of the ocean floor, and the low pressure within a storm, which slightly contribute to the bulging effect.

Because of the way storm surges can quickly inundate coastal areas and reach far inland, they typically represent one of the deadliest hurricane threats.

Part of the problem is the topography of the region. Florida’s west coast along the Gulf of Mexico is not very deep and has a gentle underwater gradient.

“The continental shelf is pretty flat,” Fritz said. “It doesn’t take much strength.”

Chris Slocum, a physical scientist at the National Oceanic and Atmospheric Administration’s Center for Satellite Applications and Research, said Hurricane Milton was approaching from the southeast – an angle that would allow it to push water directly onto the continental shelf.

In addition, sea level rise resulting from climate change has also increased the risk of flooding in the region.

It’s not clear exactly where the storm will make landfall, and small changes could make a significant difference for certain areas like Tampa Bay.

Milton was “wobbling” Tuesday, according to an early evening forecast from the National Hurricane Center. The latest modeling suggests it could hit south of Tampa Bay rather than making a direct hit, which could spare the city from the worst impacts.

In a forecast discussion, the National Hurricane Center said forecasts can vary by about 70 miles when a storm is 36 hours away from possible landfall.

“We still cannot determine the exact location of landfall, especially if further fluctuations occur in the short term,” meteorologists said.

A major hurricane has not directly hit Tampa Bay since 1921. In a report from risk modeling firm Karen Clark & ​​Co. In 2015, Tampa Bay was ranked as the most vulnerable place in the United States to storm surge from a hurricane. can act like a giant funnel, channeling and trapping floodwaters in the bay.

The city’s extensive urban development over the last century is putting more and more people and coastal structures at risk. More than 3 million people live in the metropolitan region.

“Milton has the potential to be one of the most devastating hurricanes ever for West Central Florida,” the National Hurricane Center said in a statement Tuesday.

Milton is expected to grow larger and its winds to weaken as it gets closer to land. Both factors could influence how high the storm surge becomes.

“More severe storms will be able to move more water, and large storms will move more water,” Slocum said.

Local officials in Pinellas County, which includes the cities of Clearwater and St. Petersburg, called the forecast storm surge “unsurvivable” and urged residents to follow mandatory evacuation orders.

“This is the sea coming into your living rooms,” Pinellas County Emergency Management Director Cathie Perkins said in a news conference Tuesday. “This is rapidly rising water with a lot of pressure behind it. So don’t think you’ll get through this.”

Even Florida’s east coast could be affected by a storm surge, as Milton is expected to cross the peninsula and remain a hurricane as it moves across the Atlantic Ocean again. Strong winds pull the low pressure area and possibly pull water onto land.

Northeast Florida could see a storm surge of 3 to 5 feet, the hurricane center predicts.

Storm surge is a serious problem with any major hurricane that NOAA classifies as Category 3 or higher. But lower-order storms can also produce catastrophic storm surge.

Hurricane Katrina, which reached Category 5 intensity but made landfall in Louisiana as a Category 3 storm in 2005, produced a record storm surge of 27.8 feet. In 2008, Hurricane Ike devastated the Texas Gulf Coast as a Category 2 storm, causing a 15-foot storm surge on Galveston Island.