More than 1,000 high water rescues were conducted in Harris County alone, according to the county’s fire marshal.
The rains are the result of the remnant circulation of Tropical Storm Imelda, and the rainfall totals, including a measurement of 43.15 inches southwest of Beaumont (at North Fork Taylors Bayou), vaulted the remarkably short-lived storm onto the top 5 list of all-time wettest tropical cyclones to strike the Lower 48 states. The storm’s rainfall footprint was not as extreme as Harvey’s but larger than Allison in 2001 and Claudette in 1979 - the other great tropical rain events in Texas weather records.
The National Weather Service described the event as “an incredibly dangerous, life-threatening situation” in a tweet, while the Beaumont Police Department reported over 250 high-water rescues and 270 evacuation requests on Thursday morning. The heaviest rain had moved south of the Beaumont-Port Arthur region by Thursday late afternoon.
Due to the flash flood emergencies during the day Thursday, the National Weather Service in Houston relayed a rare civil emergency message at the request of emergency management agencies in Harris, Montgomery, Liberty and Chambers counties requesting “residents stay put and shelter in place. Do not venture on to any roads in these areas.”
Texas Gov. Greg Abbott (R) declared a state of disaster in 13 counties due to flooding from the storm.
Making a major contribution to the unfolding disaster are astronomical rainfall rates — six inches per hour at times. Conroe, Tex., reported 5.16 inches between roughly 6 a.m. and 7 a.m.
Rain gauges just north of Houston recorded about 6.2 inches of rain in one hour shortly after 10 a.m., with a band of extremely heavy rain slated to move into the downtown through early afternoon. A flash flood warning was extended south to cover the entire city. In addition to the torrents, the complex of storms moving over the Houston area was a prolific lightning producer and unleashing wind gusts to 40 to 50 mph.
“If you’re in school, if you’re at work, [if] you’re at home, stay there. If you are on the road look out for high water and if possible pull over to a safe place,” tweeted Houston Mayor Sylvester Turner. Metro rail and bus services in the Houston area shut down by midday Thursday due to the widespread flooding.
George Bush Intercontinental Airport, just north of downtown Houston, recorded 2.08 inches of rain in just 27 minutes late Thursday morning and over 9 inches overall through the afternoon, making it the 5th wettest day on record. Flooding on the road leading to the terminals effectively turned the airport into an island by midday Thursday, although terminals were open and runways were not flooded.
Reports of flooding mounted in bayous on the north and east side of the city into the early afternoon.
The National Weather Service issued an online discussion warning of continued life-threatening flash flooding that shifted south and east of Houston toward Galveston Bay late Thursday afternoon.
Hardest-hit so far were communities along the Interstate 10 corridor in extreme Southeast Texas near the Louisiana border, parts of which were shut down. Radar estimates an area about 20 miles across and 40 miles long — about a dozen times larger than Washington, D.C. — picked up two feet of rain or more. The majority of this rain came down in only 12 to 18 hours, and in many cases, much less than that.
The heaviest rains fell near Beaumont, particularly on the southwest side of the city, where towering thunderstorms repeatedly washed over the same areas at their peak intensity.
At the intersection of State Highway 124 and North Fork Taylors Bayou, 35.43 inches of rain fell in the past 24 hours, according to an observation network run by Jefferson County, Texas. That weather station recorded an astounding 69-minute stretch of rainfall rates between 4 and 5 inches per hour.
Similar totals were seen at Mayhaw Bayou and Craigen Road at Taylors Bayou. These totals could climb a few inches higher, as amounts keep rising due to additional showers and thunderstorms.
Three-day rainfall totals have been historic. The weather station at State Highway 124 and North Fork Taylors Bayou recorded a storm total of 42.9 inches of rain and climbing as of Thursday afternoon. This would put Tropical Storm Imelda at number 5 on the list of wettest tropical cyclones to make landfall in the Lower 48 states, and within striking distance of Tropical Storm Claudette, which dumped 45 inches of rain in Texas in 1979.
The National Weather Service in Lake Charles issued a rare flash flood emergency, taking the unusual step of including rescue information in their bulletin: “If you cannot get through 911, call Beaumont Police Department at 409-832-1234, or Jefferson County Sheriff Office at 409-835-8411.”
Channel 12 News, the local broadcaster in Beaumont, was forced to evacuate their station Thursday morning. Roughly a foot and a half fell at their location; significantly higher amounts have fallen just to the south and west. It’s a scene eerily reminiscent of the evacuation of Houston’s CBS affiliate KHOU during Harvey in August 2017.
For days, forecasters had emphasized the wild variability in anticipated rainfall totals, as well as the possibility of extremely high rainfall totals in some spots. Just two or three miles from the 30-inch amounts, totals were closer to six inches — or less. The National Weather Service in Lake Charles, La., which serves Beaumont, warned that “any additional rainfall will cause significant and life threatening flash flooding.”
In Hamshire, Tex., about 12 miles southwest of Beaumont, there was a report of 25.75 inches of rain falling in just 12 hours, with a storm total of 33.58 inches as of about 6 a.m.
The magnitude and intensity of rainfall underscores the extreme, life-threatening, danger that exists across portions of the Texas and Louisiana Gulf Coasts. If the rain band jogs just a couple miles north or south, it could bring extreme rainfall to regions that escaped the worst so far.
In addition to the rain, the Weather Service predicted the possibility of isolated tornadoes Thursday near Beaumont. The powerful thunderstorms spurring the flooding also take on some transient supercell characteristics, allowing them to drop sporadic tornadoes. That was the case near Highlands, Tex., on Wednesday, the shear imparted by Imelda’s remnants adding a bit of extra twist to the air.
The rain should begin to taper down late Thursday night, largely dissipating by Friday morning.
Events like this are becoming increasingly frequent in part due to climate change. In nearby Houston, top-100 rain events have become twice as common since 2000 as before. Annual rainfall has also increased sharply. As the Gulf of Mexico warms and transfers more moisture into the air, it’s likely that we’ll be hearing about more top-tier rain events going forward.
It is likely, once analyses of this event are completed, it will be clear that this rainstorm will have had a likelihood of occurring of between 1 percent and 0.1 percent in any given year. Yet the odds for such extreme events may be shifting, so that what was once an exceptionally rare event is more common. This presents huge challenges for coastal Texas, where infrastructure is not designed with such shifts in mind.