1998 Tropical Storm Charley Floods

The remnants of Tropical Storm Charley brought bouts of widespread heavy rainfall to South-Central Texas between August 22 and 26, 1998. Tracking west-northwest across the Coastal Plains and Winter Garden, most locations reported between three and five inches of rainfall over this four day period. Extreme rainfall accumulations ranging between seven to greater than fifteen inches occurred over portions of the Rio Grande Plains and southern Edwards Plateau, where the remains of Charley would stall out between late August 23 and early August 24. This included reports of 15+ inches of rain in the city of Del Rio, with a maximum multi-day total of 19.05 inches occurring two miles northwest of downtown. The 17.03 inches of rainfall recorded at the Del Rio climate site on August 23 still stands as the station’s wettest twenty-four period on record, shattering the next closest observation of 8.79 inches occurring on September 13, 1935.

Tropical Storm Charley and its leftover circulation brought tragic and devastating impacts to portions of the Rio Grande Plains, southern Edwards Plateau, and Hill Country. An estimated $50 million dollars (1998 USD; ~$93 million dollars when adjusted for inflation in 2023) in damages occurred across the region between August 22 and 26, 1998. More than $40 million dollars of damages were focused in Val Verde County, where a powerful flood wave impacted the Del Rio area during the overnight hours of August 23. Thirteen people in Texas and seven in Mexico tragically lost their lives over this four day period, all due to drowning. Four of the fatalities in Texas occurred in Real County when a vehicle was swept away by rising water along the south fork of the Llano River. The other nine fatalities in Texas occurred along San Felipe Creek in Del Rio, with an additional 235 injuries being reported primarily in the Rio Grande Plains and southern Edwards Plateau. This story map explores the basic meteorology, timeline, and photographs from a truly historic South-Central Texas weather event.

1. Weak Upper Level Winds

Upper level winds remained weak and disorganized as Charley crossed South-Central Texas. Reanalysis data shows wind speeds primarily at and below 15 knots (~17 miles per hour) through the duration of the event. The weak upper level flow allowed Charley’s remains to linger across the region, elongating precipitation and heavy rainfall potential until they could vacate toward the Mexican states of Chihuahua and Sonora.

2. Persistent Ridge of Surface High Pressure

Connected to high pressure centered across the lower Mississippi Valley, a surface ridge was evident from the ArkLaTex & Sabine Basin west into the Edwards Plateau from August 23 through August 24. Surface observations showed Charley’s remnant low pressure center stalling to the south of this feature from late August 23 into the predawn hours of August 24 just west of the US-Mexico border. It would be during this period of stalling, specifically from late August 23 into the early morning hours on August 24, that extreme rainfall and devastating impacts would occur in the Del Rio area. While circumstantial, it’s possible that the aforementioned stalling was the result of Charley’s remnant low getting blocked by a combination of 1) the high terrain of the Serranias del Burro Mountains to its west and 2) the surface pressure ridge to its north. The ridge thus played a potentially critical role in the stalling of Charley’s remains between late August 23 and August 24, and the attendant catastrophic rainfall occurring in the Del Rio area.

3. Historically High Amounts of Moisture

Due in part to sustained southeasterly flow off the Gulf of Mexico, a deep fetch of moisture accompanied Charley's remains as they progressed from the Coastal Plains to the Rio Grande. One metric used to quantify atmospheric moisture is precipitable water—the total amount of rainfall that would result if all the water vapor in an imaginary vertical column of the atmosphere fell as precipitation. Soundings from Del Rio showed steady increases in precipitable water as Charley’s remains progressed west, with 2+ inch values being reported through the majority of the event. Observations recorded in the 12Z August 23, 00Z August 24, and 00Z August 25 soundings are the 8th, 7th, and 5th-highest precipitable water measurements in a sounding climatology dating back to January 1954 at Del Rio (50000+ soundings in total). Such extreme precipitable water values are extremely conducive to heavy rainfall and potentially significant accumulations. Reanalysis gives a great two dimensional visualization of the high amounts of moisture being transported into the region by Charley, with several different “surges'' of maximized values lining up nicely with multiple rounds of heavy rainfall between August 23 and 26.