Storm surge is the abnormal rise in water levels during a storm, in which heavy hurricane winds push a bulge of water toward the coast as the depth becomes shallower. Although wind is the main cause of a storm surge, it is also affected by a storm’s angle of attack, the shape of the ocean floor, and the low pressure within a storm, which somewhat promotes the bulging effect.

Because of the way storm surges can quickly inundate coastal areas and travel far inland, this is typically one of the deadliest threats from a hurricane.

Part of the problem is the topography of the region. Florida’s western coastline along the Gulf of Mexico is not very deep and has a gentle underwater slope.

“The continental shelf is quite shallow,” Fritz said. “It doesn’t take much force.”

Chris Slocum, a physical scientist at the National Oceanic and Atmospheric Administration’s Center for Satellite Applications and Research, said Hurricane Milton is approaching from the southeast — an angle that allows water to be pushed directly onto the continental shelf.

Moreover, sea level rise due to 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 substantial difference for certain areas, such as Tampa Bay.

On Tuesday, Milton “wobbled,” according to an early evening forecast from the National Hurricane Center. The latest models suggest it could strike south of Tampa Bay instead of causing a direct hit, which could spare the city from the worst effects.

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

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

Not since 1921 has a major hurricane directly hit Tampa Bay. In a 2015 report by the risk modeling firm Karen Clark & ​​Co. Tampa Bay was ranked as the place most vulnerable to hurricane flooding in the US. can act as a giant funnel, channeling and collecting the water in the bay.

The city’s extensive urban development over the past century has put more people and coastal structures at risk. The metropolitan area has more than 3 million inhabitants.

“Milton has the potential to be one of the most destructive hurricanes on record for west-central Florida,” the National Hurricane Center said in an advisory Tuesday.

Milton is expected to increase in size and winds to become weaker as it approaches land; both factors can influence how high the storm surge becomes.

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

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

“This is the ocean coming into your living rooms,” Cathie Perkins, director of Pinellas County Emergency Management, said in a news briefing Tuesday. “This is fast, rising water with a lot of pressure behind it. So don’t think you can get away with that.”

Even the east coast of Florida could see storm surge, as Milton is expected to move across the peninsula and remain a hurricane as it moves back across the Atlantic Ocean. If this happens, heavy wind gusts will affect the low-pressure system, potentially pulling water onshore.

Northeast Florida could experience a storm surge of 10 to 5 feet, the hurricane center expects.

Storm surge is a serious problem with any major hurricane, which NOAA classifies as Category 3 or higher. But even lower-level storms can cause catastrophic storm surges.

Hurricane Katrina, which reached Category 5 intensity but made landfall in Louisiana in 2005 as a Category 3 storm, produced a record storm surge of 25 feet. In 2008, Hurricane Ike devastated the Texas Gulf Coast as a Category 2 storm and caused a storm surge of 15 feet on Galveston Island.