MIAMI — With about 22 million people vulnerable to dangerous hurricane storm surges, forecasters have long struggled with how to issue warnings, especially in low-lying Florida where waters can rise far inland.

Now they have an interactive map that tracks flooding not only by location, but storm strength.

Published Thursday, the map for the first time links the coast from Texas to Maine, said Brian Zachary, a National Hurricane Center storm surge specialist. Forecasters used thousands of hypothetical hurricanes and factored in local coastal topography along with levees, canals and other structures to determine flooding.

In Florida, they found that about 40 percent of the population could face flooding in a powerful storm.

“Storm surge isn’t just, ‘I live on the coast. OK, I’m vulnerable,’ ” Zachary said. “It can go 10, 15 or 30 miles inland.”

The maps are an improvement on the disconnected grids that sometimes left the public confused. The new map lets users choose the storm size, then zoom in and out of locations, tracking flooding, which is measured at 3, 6 and 9 feet above ground.

The map arrives just as a mostly quiet Atlantic hurricane season winds down. Rather than wait until next year, Zachary said, forecasters decided to release it now to give residents more time to study it and contact local emergency managers for information on evacuation plans.

“This is for the general public to look at and say, ‘OK, I’m in a storm surge area and what should I do?’ ” Zachary said.