The rain from Harvey is in a class of its own. The storm has unloaded at least 49 inches of rain southeast of Houston, the greatest amount ever recorded from a tropical weather system in the Lower 48 states. And it’s still raining.
The National Hurricane Center broke the news:
“A preliminary report from one Texas rain gauge has broken the Texas tropical cyclone rainfall record. Southeast of Houston, Mary’s Creek at Winding Road reported 49.32 inches as of 9 am CDT. This total is higher than the previous record of 48 inches set during tropical cyclone Amelia of 1978 at Medina, Texas.”
The Hurricane Center only states that the 49-plus inches breaks the Texas record set in Medina in 1978, but the amount also represents the most from a tropical system in the Lower 48 states.
Hawaii has logged isolated reports of greater amounts at high elevations from tropical systems, but the footprint from Harvey in Southeast Texas is much larger. It has produced at least three feet of rain over most of the Houston region, affecting more than 5 million people.
“The 3-to-4 day rainfall totals of greater than 40 inches (possible 50 inches in locations surrounding Santa Fe and Dickinson) are simply mind-blowing that has lead to the largest flood in Houston-Galveston history,” the National Weather Service office Serving Houston wrote.
From the perspective of the amount of volume unloaded in the U.S. from a single storm, Harvey has no rival.
John Neilsen-Gammon, the Texas state climatologist, found Harvey’s total rainfall concentrated over a 20,000-square-mile area over 72 hours represents nearly 19 times the daily discharge of the Mississippi River, by far the most of any tropical system ever recorded.
The Space Science and Engineering Center at the University of Wisconsin-Madison determined that many areas of Southeast Texas have received rain that is expected to come around only once every 1,000 years (or having a 0.1 percent probability of occurrence), assuming a stationary climate.
This is truly an epic storm.