In Hurricane Dorian's path, citizens concerned by Trump's competency

"I'm not sure I ever heard of a category 5 hurricane. I knew they existed." President Donald Trump during FEMA meeting.

How can you know something existed but never heard about it? There have already been three since he became President, and this is the forth.

Thus Mar-a-Lago went on the market. Three potential sales collapsed before Donald Trump bought it in 1985, paying a reported $8 million for the estate and its furnishings—a small fraction of the original cost, no matter how you calculate it. And after three decades and the most confounding presidential election in living memory, Marjorie Merriweather Post’s wish for her mansion came true.

What makes a category 5 hurricane?

The highest classification in the scale, Category 5, consists of storms with sustained winds over 156 mph (70 m/s; 136 kn; 251 km/h).

What about all the others? Hurricane Katrina 2005, which he mentioned when talking about Hurricane Maria in Puerto Rico.

"Every death is a horror," Trump said. "But if you look at a real catastrophe like Katrina, and you look at the tremendous, hundreds and hundreds and hundreds of people that died, and you look at what happened here with, really, a storm that was just totally overpowering, nobody's ever seen anything like this."

Since Donald Trump has owned Mar-a-Lago, there were more President Trump should have heard about.

Hurricane Andrew was a powerful and destructive Category 5 Atlantic hurricane that struck the Bahamas, Florida, and Louisiana in August 1992. ... With a barometric pressure of 922 mbar (27.23 inHg) at the time of landfall in Florida, Andrew is the sixth most-intense hurricane to strike the United States.

And even more....
Hurricane Mitch 1998 180 mph
Hurricane Rita 2005 180 mph
Hurricane Wilma 2005 185 mph
Hurricane Matthew 2016 165 mph
Hurricane Irma 2017 180 mph
Hurricane Maria 2018 175 mph
Hurricane Michael 2018 160 mph

You can find more category 5 Hurricanes here.