RALEIGH, N.C. (WNCN) — Thursday, August 25th marks the five year anniversary of Hurricane Harvey’s landfall along the southeastern Texas Coast.

Harvey became the second most costly tropical system to make landfall in the United States, surpassed only by Hurricane Katrina.

One of the reasons Harvey was so costly was due to rapid intensification, a process which remains difficult for hurricane experts to forecast confidently.

The National Hurricane Center defines rapid intensification as “an increase in the maximum sustained winds of a tropical cyclone of at least 30 knots (35 mph; 55 km/h) in a 24-hour period.”

Though this was a rare occurrence prior to the early 2000s, it has been more common in recent years.

All ten of the most costly hurricanes to make landfall in the U.S. underwent rapid intensification, and eight of these systems occurred in the last 20 years.

These systems are extremely dangerous since they can often catch residents and officials off guard, without proper safety measures and evacuations in place.

Many hurricane experts believe rapid intensification will continue to be an increasingly frequent occurrence with landfalling tropical Atlantic hurricanes.