Tropical Storm Julia earned the distinction late Tuesday of becoming the first such system on record to form over land in Florida.
It's also the first to form over land anywhere in the USA in nearly three decades. The last storm to do so was Tropical Storm Beryl, which developed over southeastern Louisiana in 1988, according to meteorologist Phil Klotzbach of Colorado State University.
Julia's formation about 5 miles west of Jacksonville is unusual, but not unprecedented, National Hurricane Center spokesman Dennis Feltgen said.
In Julia's case, while the center of the storm technically formed over land, most of the storm's heavy rain and thunderstorms were offshore, Klotzbach said. That was also the case with Beryl in 1988, Feltgen said.
Tropical storms and hurricanes usually need warm water to thrive, but if part of the storm's circulation is over warm water, it can still develop or intensify, Klotzbach said. And if the ground is flat and soaked with water, a storm can maintain its intensity or even strengthen over land, he added.
A prime example of that situation would be Hurricane Katrina, which did not weaken significantly despite moving over land for several hours because it was going over the flat and wet Everglades, Klotzbach said.
Julia is forecast to weaken to a tropical depression later Wednesday but will still bring heavy rain to coastal areas of Georgia and South Carolina over the next couple of days, potentially causing flash floods.