Relentless rain unleashed catastrophic flooding across southeast Texas on Monday. Local officials say this was the worst flooding event the region has seen in years.
Rainfall totals across the Houston metro area varied, but some places saw nearly 17 inches in less than 24 hours. The NWS office in Houston reported 9.92 inches of rain at Houston Intercontinental Airport (IAH), making it that city’s second wettest day on record. On average, Houston typically gets 3.46 inches of rain for the entire month of April.
The intense rainfall caused bayous to swell out their banks and flood homes, businesses, and major roadways – effectively paralyzing large parts of this country’s 4th largest city. Rainfall rates reached as high as 3 to 4 inches per hour in some spots, which prompted the NWS to issue a flash flood emergency (the highest level of flood alert) for the area. Local officials say 5 people were killed and more than 100,000 people lost power as a result of the flood.
The primary driver behind this extreme rain event was also main reason why the eastern US has been unseasonably warm and dry recently. The omega block that sat over the country for the past few days basically set up a large ridge of high pressure in the east and blocked an upper-level low from moving past the Four Corners region. Essentially stuck in place, the upper-level low funneled in massive amounts of moisture from the Gulf of Mexico. That moisture was then forced to rise and cool when it interacted with the stationary front in the area. The result was an extended period of thunderstorms and intense rainfall.
Southeast Texas is no stranger to flooding. In fact, this was the fourth major flood to hit the area in the past twelve months. The previous three took place in May, June and October of 2015. But, officials in Houston say Monday’s event was the largest flood the area has seen since Tropical Storm Allison in 2001. That storm dumped more than 35 inches of rain on the Houston metro area over the course of five days and caused $5 billion worth of damage.
The Governor of Texas, Greg Abbot, has declared 9 counties to be disaster areas as a result of Monday’s storm. More rain, unfortunately, is forecast for the region this week.
View of flooding in downtown Houston, TX. Credit: KHOU