Houston, Texas rainfall was above average (49 inches) in 2015 and 2016. This was in sharp contrast to the 24 inch deficit in rainfall a few years prior. 2015 was the 5th wettest year on record for Houston, with 70.03 inches at KIAH and 77.13 inches at KHOU. Records at KIAH and KHOU, date back to 1889. Here’s a look back at the heavy rainfall events that resulted in these excessive totals:
- Widespread severe weather occurred across Texas on April 16, 2015. Thunderstorms with damaging wind gusts in excess of 60 mph and isolated, brief tornadoes impacted the Texas coastal bend and SW Houston the following day. Southern and southeastern Harris County received 4-6 inches of rain with localized 7+ inches from storms over these two days, according to the Harris County Flood Control District.
- Nearly a month later, additional thunderstorms produced localized rainfall amounts of 8-10 inches over Clear Lake, between Houston’s Beltway 8 and Galveston Bay.
- On Memorial Day (May 25, 2015), conditions became favorable for training supercell thunderstorms and excessive rainfall with W-SW flow aloft and moist inflow from the Gulf of Mexico. The National Weather
Service in Houston/Galveston issued their first Flash Flood Emergency at 10:52PM CDT. According to Harris County Flood Control District gages, 8-10 inches of rain fell from NW Houston to Sugarland during the 6 hour period from 7pm CDT on May 25 to 1am CDT on May 26. Unfortunately there were 7 flood-related fatalities during this event, the most since Tropical Storm Allison in 2001. More information on this historic event can be found here.
- The Memorial Day flood event caused May 2015 to become the wettest on record for Texas with 8.93 inches and the 2nd wettest on record for KHOU. Double-digit rainfall was widespread across the southern plains in May 2015, including Houston. 14 inches was reported at both KIAH and KHOU and 20+ inches fell on the the upper end of Brays Bayou and at Memorial Park.
- The north side of Houston experienced two consecutive months of double-digit rainfall due in part to heavy rains from Tropical Storm Bill, which tracked northwest across Matagorda Island and northward over the Texas Hill Country on June 16-17, 2015.
- On August 20, 2015 a weak surface boundary and upper-level disturbance combined with a moist airmass from onshore flow to produce clusters of heavy thunderstorms across coastal SE Texas. National Weather Service Houston/Galveston issued flash flood warnings for portions of Brazoria, Galveston, and Harris Counties that day due to a persistent area of thunderstorms producing rainfall rates in excess of 3 inches per hour.
- In late October, the remnants of Hurricane Patricia moved over northern Mexico and interacted with a surface cold front moving to the Texas coast. This resulted in widespread heavy precipitation across the region on October 24-25, 2015.
- Slow-moving thunderstorms were responsible for the 7-11 inches of rain that fell over West and Central Houston Halloween morning. Both KIAH and KHOU recorded 13 inches of rain in October.
How did 2016 compare?
In 2016, KIAH experienced record monthly rainfall in April, with a total of 14.39 inches – 9.92 inches fell on April 18th alone, making this day the second wettest on record for Houston. A strong high over the southeastern U.S. forced a surface boundary to stall in a north-south orientation over the southern plains. This combined with moist air moving onshore from the Gulf of Mexico to produce heavy thunderstorms with intense rainfall rates, especially over the northwest side of Houston. The map below is an estimate of total rainfall during April 15-18, 2016 from the Integrated Multi-Satellite Retrievals for GPM (IMERG):
In mid to late August, a stagnant weather pattern resulted in slow-moving thunderstorms across portions of Southeast Texas. High pressure over the western Atlantic drove moist southeast winds to the Gulf coast and a stalled surface boundary from Texas to the Great Lakes provided the focus for thunderstorm development. KHOU received measurable rainfall for 13 consecutive days beginning August 13, 2016, which was the longest rainfall streak in this location’s recorded history. KIAH recorded its 6th wettest August on record with 10.41 inches.