The National Weather Service is reporting 124cm of total rainfall at a site southeast of Houston, which now marks the greatest accumulation of rainfall ever recorded in the contiguous United States on account of a single tropical storm.
Water from Addicks Reservoir flows into neighbourhoods as floodwaters from Tropical Storm Harvey rise August, 29, 2017, in Houston. (AP Photo/David J. Phillip)
This latest rainfall figure still needs to be verified by other sources, but it's likely to hold — and even increase — given that Harvey is in the midst of making its third landfall, where it's expected to dump even more rain on the already waterlogged states of Texas and Louisiana. The record 124cm was recorded this morning in Mary's Creek at Winding Road, besting the previous record if 122cm.
The record for total rainfall from a tropical system has been BROKEN! Mary's Creek at Winding Road recorded 49.20", previous record is 48". pic.twitter.com/yCjuUOR8p3
— NWS Houston (@NWSHouston) August 29, 2017
According to reporting by the Washington Post, Texas state climatologist John Nielsen-Gammon recorded 127cm of rainfall midday today local time at a site 65km east of Houston.
Harvey's total concentrated rainfall, says Nielsen-Gammon, is 19 times the daily discharge of the Mississippi River — the most of any tropical system ever recorded. This tremendous amount of precipitation has fallen onto an area measuring 51,800 square km, much of it now underwater. Prior to Harvey, the wettest tropical cyclone in US history came in 1978 with the landing of tropical storm Amelia in Medina, Texas.
4 day rain total with nearly entire metro area exceeding the 1% annual chance rainfall event (100 yr) and some areas near the 0.1% (1000 yr) pic.twitter.com/12D9sHxNZD
— UW-Madison SSEC (@UWSSEC) August 28, 2017
Harvey has been called a "one in 500 years storm", but the Space Science and Engineering Center at the University of Wisconsin at Madison says this event has a probability rating of 0.1 per cent for Texas, or a "one in 1000 years" storm. But as WaPo pointed out, Houston is experiencing its third of these supposed "500 year events" in three years. So either Houston is incredibly unlucky, or the the climate models are in need of serious revision.