Tampa is the single most vulnerably city in the U.S. for hurricane storm surges, according to experts — because a mix of fatal factors collide in the city to create catastrophic conditions if it takes a direct hit from a major storm like the incoming Hurricane Milton.

About 50% of the more than 3 million people living around Tampa Bay reside at elevations less than 10 feet above sea level, a 2015 study from the disaster consultants Karen Clark and Co. found — meaning millions of homes will be severely flooded if Milton’s 15-foot storm surge comes to fruition.

The last time Tampa Bay was hit by a major hurricane was 1921, when just a few hundred people lived in sparsely developed backwater towns — and the community was still devastated, with ocean waves breaking in the middle of downtown Tampa and swaths of infrastructure being washed away.

And the area is practically tailor-made to create severe storm surges thanks to shallow depths in the bay and surrounding Gulf coast. Waves blown by heavy wind can “pile up” and create a deadly wall of water, MIT meteorology professor Kerry Emanuel told The Post.

“Storm surges are physically the same thing as a tsunami, but they’re created by wind rather than a shaking sea floor,” Emanuel said.

“Imagine a wave coming up to a place where the water’s getting shallower and shallower and shallower. It has to slow down,” Emanuel said. “The front of it is slowing down faster than the back of it. So it’s like a traffic jam. One car starts to slow down and then the other cars pile up behind it. It’s a fluid equivalent of that.”

The shape Tampa Bay itself also exacerbates that effect, Emanuel explained, as its narrow opening and channel further amplifies the surge’s pile-up and spreads it across the surrounding region.

“The water is piling up left and right, it’s not just piling up from the bottom. You have to squeeze all that energy into progressively smaller places, and it literally just gets funneled,” he said.

Finally, if Milton lands just north of Tampa, its counterclockwise rotation will slam wind and waves directly into the bay — just one more factor which led Emanuel to agree with Karen Clark and Co.’s assessment that Tampa faces surge dangers unlike any other US city.

Since the last hurricane to hit Tampa, the area has become one of Florida’s most bustling regions. In all that time it hasn’t been directly hit by another hurricane — leading experts to fear residents may not be aware of what could be coming, and choose to ignore evacuation orders.

“Unfortunately, there will be probably a higher proportion of people who refuse to leave when they ask to evacuate,” Emanuel said.

Milton strengthened to a Category 5 storm again Tuesday after a brief lull Monday night. Sustained winds are blowing at 165 mph.

Tampa could still be spared the worst of the storm as some trajectory predictions suggest it could make landfall south of the bay — with differences of just 10 to 20 miles seriously lessening the impacts created by Tampa’s topography.

Still, other predictions place the storm landing north of Tampa, or right in the heart of the bay.

Forecasters, however, have cautioned it is still far too early to know concretely where the storm will strike, and that it’s landfall won’t be known until Wednesday morning or early afternoon.

With Post wires.