Record-Breaking Rainfall from Tropical Systems
The Largest Rainfall in U.S. History
The largest rainfall from a tropical system in the U.S. was recorded during Hurricane Harvey in 2017. A little more than 60” of rain fell from August 25-29 in Nederland, Texas, a suburb of Houston.
Understanding the Factors Behind Record-Breaking Rainfall
How can we pick up so much rain from a tropical storm? It’s all about the forward speed of the system, not the intensity of the system. A slow-moving tropical storm will almost always produce more rainfall than a fast-moving major hurricane… even a category 5 hurricane. The slower the forward speed, the longer a particular area will see heavy rain.
The Case of Hurricane Harvey
Harvey made landfall as a category 4 hurricane but for most of its lifetime over the Lone Star state, it was a tropical storm. It downgraded to a tropical storm quickly but sat over the state for over four days! Multiple days of tropical rains will always spell trouble.
The Case of Debby
We are seeing something similar with Debby. Monday morning it became a tropical storm but it’s expected to drop much more rain from Georgia and points north than it did when it was over Florida as a hurricane. I bet you can guess why? Yes, its forward speed is expected to slow down dramatically. We will see widespread rainfall amounts of over a foot and some spots in the Carolinas may see 20"-30” of rain. Debby will likely go down as a prolific rainmaker.
Conclusion
Slow-moving tropical storms are more likely to produce record-breaking rainfall due to the prolonged heavy rain. Debby’s slow movement will lead to widespread flooding and heavy rain in the Carolinas and surrounding areas.
FAQs
Q: What is the record for the most rainfall from a tropical system in the U.S.?
A: The record is held by Hurricane Harvey in 2017, with over 60” of rain falling in Nederland, Texas.
Q: What is the main factor that determines record-breaking rainfall from a tropical system?
A: The forward speed of the system, not the intensity of the system.
Q: What is expected to happen with Debby’s forward speed?
A: Its forward speed is expected to slow down dramatically, leading to widespread rainfall amounts of over a foot and some spots in the Carolinas may see 20"-30” of rain.
