Derechos: Rare and serious
A recent derecho caused widespread damage in the Midwest. What exactly is a derecho, and how may insurance cover this event?
On August 10, a severe storm rolled across Iowa, Wisconsin, Illinois and Indiana that generated winds up to 130 miles per hour. Several people were injured, two died, and more than 1 million homes and businesses were without power in different states. Winds of 130 mph also occur in EF2 tornadoes and Category 3 hurricanes.
Neither tornado nor hurricane, the storm that caused this is a derecho. It traveled more than 700 miles in fourteen hours, downing fifty-foot trees in some areas. Northern Indiana and Illinois are known as a corridor of enhanced derecho activity.
What is a derecho/?
A derecho is a large group of storms producing winds of at least 57.5 miles an hour along most of its length. They extend over a path at least 250 miles long with separated gusts up to 75 mph or greater, and with no more than three hours separating individual severe wind reports.
Derechos are considered a wall of storms and are sometimes called an inland hurricane that rapidly moves across the country in a straight line, unlike a tornado. Their straight-line movement causes straight-line wind damage.
Downbursts often occur along the path of the derecho, causing variations in wind speeds along the length of the storm; a derecho can comprise of families of downburst clusters that extend continuously for 250 miles or more. It is important to remember that these strong winds cover a much broader area than a tornado, leading to significant damage over a large area.
They are associated with bands of showers or thunderstorms that assume a bowed shape, which are called bow echoes or squall lines. Heatwaves are often the trigger for a derecho, as the mixing of air temperatures between warm and cold air can lead to thunderstorms and the potential for derechos. Therefore, derechos are most common in summer, and some of the most serious events have occurred on the fringes of major heat waves.
They occur most commonly between May and August, with 75% occurring between April and August, which is also thunderstorm season. Derechos are difficult to predict, although thunderstorm predictions are quite accurate and should be paid attention to. Derechos most commonly occur from the upper Mississippi Valley into the Ohio Valley, and from the southern Plains northeast into the mid-Mississippi Valley.
Like tornadoes and hurricanes, derechos can cause significant damage. Vehicles are vulnerable to falling trees and utility poles, and vehicles that are high profile such as buses, trucks, SUVs and tractor-trailers are susceptible to being blown over. Mobile homes are also susceptible to being blown over, as well as silos and barns.
The stronger the winds, the more significant the damages
Roofs can be blown off, or trees may be blown onto them, and power lines are particularly susceptible to be taken down by high winds and falling trees. Flash floods are also possible, as a stationary band of thunderstorms sometimes occurs at the rear of a derecho system. This leads to both wind and water damage.
This is rather typical damage from any wind or rain storm; what is not typical, however, is the amount of crop damage due to the size of the storm and the strength of the winds. Strong winds covering 250 miles can damage a huge number of crops. The governor of Iowa estimates that 10 million acres of corn and soybean fields have been flattened, which is up to 43% of the land in the state used for crops.
The damage is such that it shows up on weather radar. Estimates are that 180 to 270 million bushels of corn were affected. Since some corn was flattened and not snapped, experts are not sure yet as to the extent of damages, but it is likely to be in the billions of dollars.
Affected houses, cars, businesses, and business vehicles will be covered under their standard property policies, which generally insure wind damage. Flash floods will likely not be covered unless the property was insured for flood, and other water loss coverage will depend on the actual property damage. The crops, however, given their size, will be covered by crop insurance, which is designed to cover such natural disasters.
The USDA has resources for those needing assistance after the storm here.
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