The 3 Biggest Rainfall Events Ever Recorded In United States Happened In The Past 3 Years
Preliminary research by precipitation expert Dr. Kenneth Kunkel of the North Carolina Institute for Climate Studies, announced in September, found that the three highest-volume rainfall events in the U.S. in the last 70 years have occurred since 2016: Hurricane Harvey in Texas/Louisiana in 2017, Hurricane Florence in North Carolina in 2018, and a March 2016 storm in Louisiana. It is highly unusual to get three such extreme events in one three-year period, and the odds of this occuring were increased by global warming, which boosts the amount of water vapor in the air and increases the frequency and intensity of heavy precipitation events.
Dr. Kunkel’s ratings were based on four-day rainfall totals over an area of 14,000 square miles (an area 40% larger than the state of Maryland). Harvey delivered an average of 25.6 inches of rain over an area of 14,000 square miles, while Florence was a somewhat distant second place, with an average of 17.5 inches of rain over a like-sized area.
Figure 1. The top 30 highest-volume U.S. four-day rainfall totals over areas of 14,000 square miles since 1949. Hurricane Harvey and Hurricane Florence rank #1 and #2. Image credit: Dr. Kenneth Kunkel, North Carolina Institute for Climate Studies.
The analysis only used stations that have been reporting reliably throughout the 70-year period, so only a small fraction of current reporting stations were used. However, the use of a consistent network of stations across the entire period increases the reliability of the resulting rankings. When looking at a bigger area--20,000 square mile--Harvey remained in first place, 1998?s Hurricane Georges was second, and Hurricane Florence fell to seventh place. The analysis has not been published or peer reviewed yet, but will be presented at the January 2019 meeting of the American Meteorological Society, Kunkel said. Below is a short description of the top-ten list of highest-volume U.S. rainfall events over a 14,000 square mile area over the past 70 years.
Figure 2. Storm-total rainfall from Hurricane Harvey, August 24 – 31, 2017. Harvey dumped over 40” (yellow colors) in Houston, with isolated amounts in excess of 50” (pink colors) south of Houston and northwest of Port Arthur. Image credit: NOAA.
1) Hurricane Harvey, August 27 – 30, 2017: 25.6” over 14,000 square miles
Hurricane Harvey hit Rockport, Texas as a Category 4 hurricane with 130 mph winds on August 25, 2017, then stalled just west of Houston for two days, dumping prodigious rains. The storm then drifted out to sea, and made another landfall near Beaumont, Texas, dumping catastrophic rains of more than 25 inches in 24 hours. A total rainfall amount in excess of 60” was recorded at two locations near Port Arthur, Texas—the heaviest rainfall ever recorded in the U.S. from a tropical cyclone. Harvey dumped more than 30 inches of rain on 6.9 million people, while 1.25 million experienced over 45 inches and 11,000 had over 50 inches, based on 7-day rainfall totals ending August 31. Harvey caused $128 billion in damage and killed 89 people. Four attribution studies published in 2017 and 2018 have found that human-caused global warming made Harvey’s heavy rains more likely.
EDIT
https://www.wunderground.com/cat6/3-Highest-Volume-US-Rainfall-Events-Record-Have-Happened-Past-3-Years
