A violent thunderstorm complex tracked across eastern Texas, including downtown Houston, in the evening hours of May 16 killing at least seven people. The storms generated exceptional wind damage to both residential and commercial properties, infrastructure, and vegetation. Statewide, more than one million customers were left without electricity at the peak of the incident. According to the National Weather Service (NWS), straight-line winds (thunderstorm related winds) were estimated to have reached 100 mph (160 kph), equivalent to those seen in a Category 1 hurricane.
The NWS Houston office confirmed that this thunderstorm complex met the official definition as a derecho (a widespread, long-lived windstorm). Winds were powerful enough to blow out windows from skyscrapers, damage roofs of hotels and residential structures, down many trees, and topple transmission towers. The storm cluster concurrently tracked hundreds of miles across the Southeast overnight, where additional wind and flooding related impacts were incurred. Total economic and insured losses were each individually expected to exceed USD1+ billion, with the loss potential being notably higher than this figure and ending as a multi-billion-dollar financial cost.
This event showed the magnitude of damage non-tornadic thunderstorm winds can generate, particularly when they impact a densely populated and highly exposed area - such as the Houston metro. And it continued a highly active period for US SCS losses which began in late-April. It is expected to become the second billion-dollar SCS insurance industry loss event in May, following the May 6-10 outbreaks which impacted the central and eastern US. Year-to-date US SCS public and private insured losses are already nearing USD17 billion as of the first half of May and remain on track to surpass the USD20 billion threshold for the ninth consecutive year. Annual US insured SCS losses in the last decade (2014-2023) have averaged USD31 billion. This is much higher than the longer-term 21st Century average of USD22 billion. (Loss averages in today’s dollars.)
Impact Summary
The line of thunderstorms which tracked from central Texas into northern Florida between May 16-17 generated widespread wind damage to homes, infrastructure, vehicles, and vegetation. They produced instances of impactful flash-flooding across the southeastern US. Very large hail (2.0+ in / 5.1+ cm) was likewise reported in localities of Reagan, Ector, and Mason counties in Texas. As of this writing, seven storm related fatalities have been confirmed.
In Houston, high winds shattered windows from downtown skyscrapers and damaged the roof of a hotel. The most notable damage occurred to buildings located near Louisiana Street. The NWS estimated winds peaked at nearly 100 mph (160 kph) in downtown Houston and gusted 90 to 100 mph (145 to 160 kph) in Baytown & Galena Park. Following the event, a local state of disaster was declared for the City of Houston. A federal disaster declaration was subsequently approved for seven Texas counties, authorizing Federal Emergency Management Agency (FEMA) extends more than 240 miles (385 kilometers) and includes wind gusts of at least 58 mph (93 kph) or stronger along most of its length, the event is classified as a derecho.
At the peak, more than one million customers in the state were left without electricity, most of whom were in Harris County. Local officials reported at least 30% of the county population experienced outages. In some instances, power restoration could take weeks. Prolonged power outages were particularly concerning as daily high temperatures in subsequent days reached into the 90s (°F).
Transportation across the city was severely impacted as fallen trees, glass, electrical wires, and debris covered local streets. In total, nearly 2,500 traffic signals were out. Emergency officials urged residents to avoid travel when possible, and many schools and businesses were temporarily shuttered.
Three EF1 tornadoes were confirmed in Texas (2) and Louisiana (1). In Texas, numerous homes sustained tornadic damage near the town of Cypress in Harris County. Additional notable SCS related impacts were incurred in Louisiana and included damaged homes and vehicles. At the New Orleans airport, damage to aircraft equipment was reported.
Financial Loss Commentary
The May 16-17 economic and insured SCS losses are each anticipated to exceed the USD1 billion threshold. This would mark the seventh billion dollar insured SCS event in the US in 2024. The loss potential for this event is notable, and it is entirely possible that this ends as a multi-billion-dollar financial cost. Damage was primarily driven by severe wind impacts to residential and commercial structures. Additional losses to motor, infrastructure, and agribusiness were incurred. Houston and the western Gulf Coast in general have been particularly vulnerable to natural disasters in recent years.
This event is a reminder that Texas remains susceptible to large loss due to the lack of a consistent building code in the state. A recent study by the Insurance Institute for Business and Home Safety (IBHS) notes that Texas is near the bottom among Atlantic and Gulf Coast states when evaluating building code quality and readiness. This does not suggest that better codes would have fully or significantly reduced the damage from the recent storms, but it likely would have helped mitigate against some of it.
Although on a much smaller geographic scale, the intensity of this event brought memories of the infamous August 2020 Midwest derecho. That event remains a notable outlier in terms of historical SCS losses as the total economic cost from the individual derecho and damage from other storms during that outbreak topped USD16 billion (2024 USD). Public and private insurers covered USD11 billion of that total. A large portion of losses during the 2020 derecho were likewise driven by straight-line winds, which included catastrophic impacts to local agriculture across Iowa and Illinois. The May 16-17 event did not spawn nearly as extensive of a footprint.
Year-to-date US SCS public and private insured losses are already approaching USD17 billion as of the first half of May and remain on track to surpass the USD20 billion threshold for the ninth consecutive year. Annual US insured SCS losses in the last decade (2014- 2023) have averaged USD31 billion. This is significantly higher than the longer-term 21st Century average of USD22 billion. (Loss averages in today’s dollars.)
Please note that further US SCS losses have already occurred since the May 16-17 outbreak. Another powerful and damaging derecho led to major impacts across parts of Kansas, Oklahoma, Missouri, Illinois and elsewhere in the Plains and Midwest on May 19-20. Per the Storm Prediction Center (SPC), even further widespread SCS activity was forecast in the Plains and Midwest on May 21-22 with several notable metro areas at risk: Kansas City, MO, Des Moines, IA, Madison, WI, St. Louis, MO, and Chicago, IL.
Background: Meteorological Recap
The storms and incessant rains which affected eastern Texas and the Southeast on May 16-17 formed along the northern periphery of a large heat dome which aided in bringing an unseasonably warm and moist airmass to regions of the southern US. Interactions between this warm and unstable air and frontal boundaries generated high rainfall rates and ignited severe storms.
An expansive complex of thunderstorms, also referred to as a mesoscale convective system (MCS), evolved across central Texas in the late afternoon of May 16. In subsequent hours, this system intensified upon approach to the Houston region, prompting tornado warnings and particularly dangerous situation (PDS) severe thunderstorm warnings. The National Weather Service (NWS) alerted that the winds associated with a small bowing complex, which impacted highly populated regions of Harris County (Texas), were anticipated to exceed 80 mph (130 kph). The storm complex continued propagating eastward overnight, producing additional severe wind reports in southern Louisiana, southern Alabama, and the Florida Panhandle. This derecho event yielded station measured wind reports as high as 84 mph (135 kph) outside of New Orleans in Kenner, Louisiana and 87 mph (140 kph) near Port Saint Joe, Florida. Preliminary data from the SPC local storm reports indicated that at least 120 instances of filtered severe straight-line winds were reported on May 16 alone, defined as gusts reaching 58 mph (93 kph) or stronger.
In addition to severe weather, the intensity and slow-moving nature of the storms in tandem with rain falling on already saturated soils resulted in localized flooding and flash-flooding across parts of Texas and the Gulf Coast. In fact, the Weather Prediction Center (WPC) issued a ‘High Risk’ (level 4 of 4) for excessive rainfall across eastern Texas and western Louisiana on May 16. Note then even though ‘High Risk’ days only account for approximately 4% of days in a year, they historically generate nearly 80% of all flooding related damages in the US. Many regions in northeastern Texas have received more than 400% of normal rainfall over the past 30 days.
For further context regarding US derecho climatology, NOAA research suggests that May, June, and July account for nearly two-thirds of annual derecho activity. May (22%), June (20%), and July (21%) are the start of peak heating months in the US and amplify the “Ring of Fire” weather pattern which sees an active jet stream usher in moisture and heat wrapping around the outer periphery of a strong ridge of high pressure. This creates synoptic conditions ideal for derecho environments.
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