Storm

• 1. Introduction

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  A storm is any disturbed state of the natural environment, and it can rip across worlds far beyond our own. On Jupiter, a single storm called the Great Red Spot has raged for at least 340 years. It is larger than the entire Earth. The astronomer Giovanni Domenico Cassini first observed it centuries ago, and it still turns today. Closer to home, the English word storm traces back to Proto-Germanic sturmaz, meaning noise and tumult. Its synonym, tempest, came from French. But what actually sets a storm in motion? Why does one fall of snow shut a city while another saves a harvest? And how did a single hurricane help wreck a Spanish-French struggle for a continent? The answers move between low-pressure centers and high mountains, between Mars and the Sea of Galilee, between a denting hailstone and a Booker Prize-winning novel.

• 2. Anatomy Of A Storm

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  A center of low pressure develops, and a system of high pressure surrounds it. That clash of opposing forces can stir winds and pile up storm clouds such as cumulonimbus. The recipe scales down as well as up. Hot air rising off hot ground forms small localized low-pressure pockets, producing dust devils and whirlwinds. Thunderstorms reveal the engine in full. They occur where high levels of condensation form in unstable air that drives deep, rapid upward motion. The heat energy creates powerful rising currents that swirl up to the tropopause, while cool descending air produces strong downdraughts below. Once the storm spends its energy, the rising currents die away and the downdraughts break up the cloud. Individual storm clouds can measure between 2 and 10 kilometers across. By a strict meteorological definition, a terrestrial storm is a wind measuring 10 or higher on the Beaufort scale. That means a wind speed of 24.5 meters per second, or 89 kilometers per hour, or 55 miles per hour, though popular usage is far looser. Such storms can last anywhere from 12 to 200 hours, depending on season and geography.

• 3. A Taxonomy Of Fury

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  A blizzard brings gale-force winds and heavy snow accumulating at a rate of at least 5 centimeters per hour, with very cold conditions below roughly minus 10 degrees Celsius. In the United States, that temperature criterion has lately fallen out of the definition. The variety of storms is startling. A bomb cyclone is a rapid deepening of a mid-latitude low-pressure area, with winds as powerful as a typhoon or hurricane. A derecho is a widespread, long-lived, straight-line wind storm tied to a fast-moving group of severe thunderstorms. A firestorm grows so intense it creates and sustains its own wind systems. The Peshtigo Fire stands as one example, and the aerial bombings of Dresden produced one deliberately. Tornadoes carry their own dark reputation. A tornado is a violent, destructive whirlwind on land, usually appearing as a dark, funnel-shaped cloud and often preceded by thunderstorms and a wall cloud. Though they form all over the planet, the interior of the United States is the most prone area, especially across Tornado Alley. Tropical cyclones, by contrast, are warm-core systems fueled by the heat released when moist air rises and condenses. Depending on strength and location, they go by names such as tropical depression, tropical storm, hurricane, and typhoon.

• 4. When The Sky Strikes Back

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  In the United States, major hurricanes make up just 21 percent of all landfalling tropical cyclones, yet account for 83 percent of all damage. The destruction reaches into every system a society relies on. These storms knock out power to tens or hundreds of thousands of people, and they destroy key bridges, overpasses, and roads. That cripples efforts to move food, clean water, and medicine where they are needed. The single deadliest force is rarely the wind. The storm surge, the rise in sea level driven by a cyclone, is typically the worst effect of a landfalling tropical cyclone. It has historically caused 90 percent of tropical cyclone deaths, moving miles inland and cutting off escape routes. The damage is staggering in scale. The Food and Agriculture Organization of the United Nations has calculated that storms caused 720 billion US dollars of damage between 1991 and 2023. Lightning brings its own dangers. In areas with frequent cloud-to-ground lightning, like Florida, it causes several fatalities a year, most often to people working outside.

• 5. Ice, Hail, And Record Stones

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  Just 8 millimeters of ice accumulation can begin downing power lines and tree limbs, especially in breezy conditions. Ice storms rank among the most dangerous winter storms. They form when surface temperatures sit below freezing but a thick layer of above-freezing air remains aloft, so rain falls into the freezing layer and freezes on impact into a glaze. They can last from hours to days and cripple small towns and large cities alike. Hail writes its records in weight and width. Most hail is small and nearly harmless, but stones greater than 2 inches in diameter can cause serious damage and injury. One of the earliest recorded incidents occurred around the 9th century in Roopkund, Uttarakhand, India. The largest hailstone ever recorded in the United States fell on the 23rd of July 2010 in Vivian, South Dakota. It measured 8 inches in diameter and 18.62 inches in circumference, weighing 1.93 pounds. That broke the diameter record set by a 7-inch stone in Aurora, Nebraska on the 22nd of June 2003, and the weight record set by a 1.67-pound stone in Coffeyville, Kansas in 1970. The crops most sensitive to hail are wheat, corn, soybeans, and tobacco, and hail ranks among Canada's most expensive hazards.

• 6. The Useful Side Of Storms

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  Japan receives over half of its rainfall from typhoons. Storms are not purely destructive, and some regions depend on them. Systems with significant rainfall and duration help relieve drought in the places they pass through. Hurricanes in the eastern north Pacific often supply moisture to the Southwestern United States and parts of Mexico. Hurricane Camille shows the strange dual nature plainly. It averted drought and ended water deficits along much of its path, yet it also killed 259 people and caused 9.14 billion US dollars in damage, measured in 2005 dollars. Snow can be an ally too. Accumulated snow serves as a thermal insulator, conserving the heat of the Earth and shielding crops from subfreezing weather. Some agricultural areas rely on a winter snowpack that melts gradually in spring to water their crops. Heavy snowfall also opens recreations otherwise impossible, like skiing and snowmobiling. In Yamagata Prefecture, Japan, people harvest snow and store it surrounded by insulation in ice houses. That stored snow cools and air-conditions through the summer using far less electricity than traditional methods.

• 7. Storms Beyond Earth

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  In September 1994, the Hubble Space Telescope used its Wide Field Planetary Camera 2 to image storms on Saturn driven by upwelling warmer air, much like a terrestrial thunderhead. The storm had been observed earlier, in September 1990, and earned the name Dragon Storm. Earth holds no monopoly on bad weather. Any planetary body with a sufficient atmosphere, giant planets in particular, can undergo stormy weather. Neptune had its own lesser-known Great Dark Spot. Mars stages dust storms that can cover the entire planet, tending to occur when Mars comes closest to the Sun, and shown to raise its global temperature. One such storm was studied up close by chance. When Mariner 9 became the first spacecraft to orbit another planet, arriving at Mars on the 14th of November 1971, scientists found the atmosphere thick with a planet-wide robe of dust, the largest storm ever observed there. The surface was totally obscured, so Mariner 9's computer was reprogrammed from Earth to delay imaging for a couple of months. Two extrasolar planets are also known to have storms. The storm on HD 209458 b was discovered on the 23rd of June 2010 and measured at 6200 kilometers per hour, while HD 80606 b produces winds of 17700 kilometers per hour across its surface.

• 8. Tempests In Art And Faith

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  On Saint James Day in 1609, the Sea Venture was caught in a hurricane that raged for nearly two days between Cuba and the Bahamas. The vessel struck a coral reef near Bermuda, yet all aboard survived for nearly a year on the island, which the British colonists then claimed and settled. That wreck inspired Shakespeare's play The Tempest, written in 1611. Storms have shaped scripture and myth for far longer. According to the Bible, a giant storm sent by God flooded the Earth, and the rain fell forty days and forty nights while Noah and his family sheltered in the Ark. In the New Testament, Jesus Christ is recorded calming a storm on the Sea of Galilee. The Gilgamesh flood myth carries a similar deluge in the Epic of Gilgamesh, and in Greek mythology Aeolus keeps the storm-winds, squalls, and tempests. The tornado entered American imagination through L. Frank Baum's The Wonderful Wizard of Oz, illustrated by W. W. Denslow. Published by the George M. Hill Company in Chicago on the 17th of May 1900, it sweeps Dorothy Gale from her Kansas farm to the Land of Oz. Hollywood director King Vidor survived the Galveston Hurricane of 1900 as a boy, and later wrote a fictionalized account titled Southern Storm for the May 1935 issue of Esquire. That hurricane sits at the center of Erik Larson's 2005 book Isaac's Storm, which also chronicles the rivalry between the early Weather Bureau and the weather service in Cuba.