Since 1980, severe storms have caused over $383 billion in total damages, with over a third of the total 163-billion-dollar storm events occurring in the past five years. As baseline temperatures rise, the threat of severe storms increases. Warmer air holds more moisture, enabling stronger thunderstorm events and impacting more communities as developments push into storm-threatened regions.
What are Severe Storms?
A severe storm produces wind gusts of at least 58 mph, hail one inch or larger in diameter, and/or tornadic activity (NOAA). Flash flooding is also associated with severe storm threats. There are about 100,000 thunderstorms each year in the US. About 10% of these reach severe levels (NOAA).
Thunderstorms form when warm, moist air rises into cold air and condenses into a rain event with lightning occurring from within the cumulonimbus cloud (aka anvil clouds). Thunder comes from lightning, so, all thunderstorms have lightning as a convective feature. Lightning occurs as the negative charges (electrons) in the bottom of the cloud are attracted to the positive charges (protons) on the ground (UCAR). Temperatures in the air of a lightning channel may reach as high as 50,000-degrees Fahrenheit, five times hotter than the sun.
Hail forms when raindrops are carried upward by thunderstorm updrafts into extremely cold areas of the atmosphere and freeze. Hailstones grow by colliding with liquid water freezing onto the hail. With rising baseline temperatures, smaller hail pellets begin to melt before reaching the surface causing larger hailstones to become the main hail event going forward.
Tornadoes are narrow, violently rotating columns of air that extend from the base of a thunderstorm to the ground. About 1,200 tornadoes occur in the US annually.
Severe storm data at a glance
Storm damage costs billions of dollars
Each year since 2008 has produced at least $10 billion in US insured damage from severe weather, according to the reinsurance firm Aon. That's more than four times the inflation-adjusted damage rate of the 1980s.
Tornadoes are more common
2021 produced 177 more tornadoes than average. In March 2022 there were 236 tornadoes, which was more than any month’s average over the past 14 years.
In the past decade, tornadoes have caused more than $14.1 billion in total damage to property and crops across the US. From 2010 through 2020, tornadoes resulted in $2.5 million in property damage per storm.
Impacts to Critical Infrastructure Sectors from Severe Storms
The threat to critical infrastructure owners and operators comes from the initial storm damages due to lightning, large hail, high wind damages, tornadoes, and local flooding events then the secondary impacts such as delayed power restoration, riverine flooding from runoff, delayed or damaged supply chain operations, sanitation threats, water sector degradation, structural instability delaying return to operations, and impacts throughout the community from debris, evacuations, and outages.
As developments in hazardous areas continue and atmospheric instability increases, critical infrastructure sites will see increased damage reports that include:
Uprooted objects, including trees, furniture and pieces of houses causing damage along the storm path.
Hail damaged vehicles, glass, siding, exposed metal, and most roofing types resulting in microfractures, dents, mineral loss, or material separation
Power outages leading to equipment cost increases for utilities and supply chain delays extending outage periods
“Blown” transformers or breakers on the lines or trigger a safeguard shutdown of the energy equipment due to lightning strikes
Damaged or downed powerlines. Most can withstand winds around 55mph, while severe storms can produce winds over 75 mph
Damaged surface soils, fences, barns, livestock, homes, exposed pipes, water quality, and various supporting infrastructure to agricultural operation as the scale of impact can range multiple states
Rapid surges of water runoff with short notice due to downpouring rain events causing upstream rivers to runover into local streams or low-lying areas
Damage to transportation includes derailed trains, damaged roadways, miles-wide debris fields, downed live powerlines, potential aviation damage and delays, and impacts across trucking and standard vehicle movements.
Pipelines damage from soil slips in flash floods and straight-line and tornadic wind damage, reducing flows or damaging equipment.
Severe Storm Resources
Learn more about severe storms and the risks they pose to critical infrastructure systems.
“A nationwide 6.6% increase in supercells and a 25.8% jump in the area and time supercells stay over land and cause destruction by the year 2100.”
There has been a large decrease in the number of days per year with at least 1 F1-F5 tornado since the 1970s, along with a large increase in the number of days per year with numerous F1-F5 tornadoes.
Doubling of greenhouse gases in the atmosphere would significantly increase the number of days that severe thunderstorms could occur in the southern and eastern US. Cities like Atlanta and New York could see a doubling of potential severe storm days.
Climate change is expected to intensify storms and lead to greater precipitation across the entire region during this century.
Climate change is projected to increase the frequency and intensity of storms in all regions of the US. These storms can lead to extreme flooding and other impacts that can overwhelm or damage water infrastructure.