Tropical Storm Ian is marching toward the Gulf Coast of the U.S., a region quite vulnerable to hurricanes.

The underwater geology of the Gulf of Mexico is what makes the Gulf Coast particularly unguarded to the massive influx of seawater, said Michael Brennan, acting deputy director of the National Hurricane Center, according to an article on Inside Science.

The symmetry of the Gulf of Mexico, with its shallow, sloping continental shelf, allows the storm surge to be pushed even higher onto land, Brennan told the outlet.

Because the land around the Gulf Coasts is typically flat, that exacerbates the flooding even more and allows the storm surge to travel farther inland, Brennan said.

"Of all of the hazards of hurricanes --- winds, rain, storm surges –-- surges are what can cause the largest loss of life," Brennan told Inside Science.

The Tampa Bay-St. Petersburg area, one of the regions bracing for Ian, is especially vulnerable to storm surge flooding but has avoided a direct hit from a strong hurricane since 1921.

Editor's Note: This post has been updated to reflect proper attribution to Inside Science.

-ABC News' Max Golembo

Florida Gov. Ron DeSantis is imploring Floridians to prepare for Tropical Storm Ian, no matter which side of the state they live on.

While Ian is forecast to make landfall on the west coast or panhandle of Florida in a matter of days, DeSantis warned those not in its direct path against a false sense of security.

"Just don't think that if you're not in that eye, that somehow you don't have to make preparations," DeSantis said during a news conference on Sunday. "The last thing we want to see you see it start to really bear east quickly and then have folks who are not prepared."

DeSantis, who has declared a state of emergency ahead of the storm, will be requesting assistance from FEMA, he said.

About 2,500 Florida Nationals Guardsman have been activated to respond to the storm.

-ABC News' Miles Cohen

NASA engineers will decide on Sunday whether to remove the Artemis rocket from the launchpad at the Kennedy Space Center in Cape Canaveral, Florida.

Officials plan to meet at 7 p.m. to look at the latest data and determine how soon or if they need to take Artemis off the launch pad.

The launch of the rocket has already been postponed twice — once in August due to technical glitches and another earlier this month due to a fuel leak.

If the launch is not delayed again, the attempt to launch on Oct. 2 will remain in place.

-ABC News' Gina Sunseri

Ian remains a tropical storm with winds of 50 mph, but the storm system is expected to rapidly intensify on Sunday as it moves over warm waters in the Caribbean Sea, according to the National Hurricane Center.

The seawater currently carries very favorable conditions for strengthening over the coming days, with temperatures between 85 and 90 degrees Fahrenheit -- the perfect temperatures for fueling a powerful storm as it stays over open water.

Ian is expected to strengthen to a hurricane by Sunday night and into a major hurricane later Monday night as it passes by Cuba.

The NHC currently forecasts Ian to strengthen into a major Category 4 hurricane on Tuesday in the Gulf of Mexico as it heads toward Florida.

Ian is expected to make landfall on the west coast or the panhandle of Florida on Wednesday or Thursday.

Some weakening could occur before the storm system makes landfall, possibly dipping below major hurricane status before impacting coastal communities.

A hurricane warning is currently in effect for the western portion of Cuba, where flooding rains and major storm surge are forecast.

-ABC News' Riley Winch

Caribbean islands such as Jamaica and Grand Cayman will start to experience the effects from the outer bands of Tropical Storm Ian within the next 24 hours, forecasts show. The islands will experience conditions such as heavy rain, possible flash flooding and storm surge.

The storm system will begin to rapidly intensify overnight into Monday before it closes in on western Cuba on Monday night.

As of 2 p.m., the sustained winds in the tropical storm remained at 50 mph as it moved west-northwest at 12 mph, the center about 265 miles away from Grand Cayman.

Hurricane warnings are in effect for Grand Cayman and western Cuba, while tropical storm warnings and watches are in effect in other portions of both islands.

As a hurricane, Ian is expected to peak at a Category 4 before weakening slightly as it looks to make landfall on the west coast or panhandle of Florida in the coming days.

There is still some uncertainty to the track Ian will take once the system enters the Gulf of Mexico.

The center of the storm and the worst of the impacts could end up heading toward the western coast of Florida's peninsula, including the Tampa area. The other possible scenario has the storm moving more due north and bringing a possible landfall along the Florida peninsula, impacting cities like Panama City and Tallahassee with more direct effects.

The storm will begin to impact the Florida keys and the southern portions of the state by Tuesday night.

-ABC News' Dan Peck