Instruct: Given a question, retrieve relevant passages that can help answer the question.
Query: What country has the most tornados?
The United States has the most tornadoes of any country, nearly four times more than estimated in all of Europe, excluding waterspouts. This is mostly due to the unique geography of the continent. North America is a large continent that extends from the tropics north into arctic areas, and has no major east-west mountain range to block air flow between these two areas. In the middle latitudes, where most tornadoes of the world occur, the Rocky Mountains block moisture and buckle the atmospheric flow, forcing drier air at mid-levels of the troposphere due to downsloped winds, and causing the formation of a low pressure area downwind to the east of the mountains. Increased westerly flow off the Rockies force the formation of a dry line when the flow aloft is strong, while the Gulf of Mexico fuels abundant low-level moisture in the southerly flow to its east. This unique topography allows for frequent collisions of warm and cold air, the conditions that breed strong, long-lived storms throughout the year. A large portion of these tornadoes form in an area of the central United States known as Tornado Alley. This area extends into Canada, particularly Ontario and the Prairie Provinces, although southeast Quebec, the interior of British Columbia, and western New Brunswick are also tornado-prone. Tornadoes also occur across northeastern Mexico.
36 people died in this tornado, and over 8,000 homes were badly damaged or destroyed. The tornado caused $1 billion in damage, making it the second-costliest tornado in U.S. history, and the most costly in history from 1999 to 2011, at which point it was surpassed by the 2011 Tuscaloosa–Birmingham tornado and again by the 2011 Joplin tornado. It was also the deadliest tornado to hit the U.S. since the April 10, 1979 F4 tornado that hit Wichita Falls, Texas, which killed 42 people.
Overall, the tornado killed 158 people (with an additional three indirect deaths), injured some 1,150 others, and caused damages amounting to a total of $2.8 billion. It was the deadliest tornado to strike the United States since the 1947 Glazier–Higgins–Woodward tornadoes, and the seventh-deadliest overall.
The tornado outbreak sequence of May 21–26, 2011 was one of the largest tornado outbreaks on record which affected the Midwestern and Southern regions of the United States. Most of the tornadoes developed in a corridor from Lake Superior southwest to central Texas; isolated tornadoes occurred in other areas. An especially destructive tornado destroyed one-third of Joplin, Missouri, resulting in 158 deaths and over 1,000 injuries. The Joplin tornado is the deadliest in the U.S. since April 9, 1947, when an intense tornado killed 181 in the Woodward, Oklahoma area. Tornado-related deaths also occurred in Arkansas, Kansas, Minnesota, and Oklahoma. Overall, the tornado outbreak resulted in 184 deaths, 6 of those non-tornadic, making it second only to the 2011 Super Outbreak as the deadliest since 1974, and the second costliest tornado outbreak in U.S. history behind that same April 2011 outbreak, with insured damage estimated at $4–7 billion.
Although the official boundaries of Tornado Alley are not clearly defined, its core extends from northern Texas, Oklahoma, Kansas, Nebraska, into South Dakota. States such as Missouri, Iowa, Minnesota, Wisconsin, Illinois, Indiana, and western Ohio are sometimes included in Tornado Alley. Some research suggests that tornadoes are becoming more frequent in the northern parts of Tornado Alley where it reaches the Canadian prairies.
The Midwestern states are very prone to tornado activity, as they are part of "Tornado Alley." States included in the area that are hit by tornadoes the most are Oklahoma, Kansas, Missouri, Nebraska, Iowa, and South Dakota. The Midwestern States are often hit by tornadoes during the late spring and early summer months, especially the months of May and June. This is due to the aforementioned air mass moving northward into the Midwest and combining with another air mass that move southward from Canada. This creates unstable air, creating the potential for storms to strike the most during these months. The frequency begins to decrease in the middle of the summer, as the air mass moves northward into the Great Lakes states.
Similar to fatalities, damage (and observations) of a tornado are a coincidence of what character of tornado interacts with certain characteristics of built up areas. That is, destructive tornadoes are in a sense "accidents" of a large tornado striking a large population. In addition to population and changes thereof, comparing damage historically is subject to changes in wealth and inflation. The 1896 St. Louis–East St. Louis tornado on May 27, incurred the most damages adjusted for wealth and inflation, at an estimated $2.9 billion (1997 USD). In raw numbers, the Joplin tornado of May 22, 2011 is considered the costliest tornado in recent history, with damage totals near $2.8 billion (2011 USD). Until 2011, the "Bridge Creek-Moore tornado" of May 3, 1999 was the most damaging.
It has also been asserted that there are numerous Tornado Alleys. In addition to the Texas/Oklahoma/Kansas core, such areas include the Upper Midwest, the lower Ohio Valley, the Tennessee Valley and the lower Mississippi valley. Some studies suggest that there are also smaller tornado alleys located across the United States.
The Enhanced Fujita Scale classifies tornado strength from weakest, an EF0 tornado, to strongest, an EF5 tornado, by the damage the tornado caused to property and infrastructure. An EF0 tornado has winds from 65–85 MPH (105–137 KPH), may take off a roof or damage gutters, and can bring down tree limbs. If a tornado causes no damage because it did not occur in a populated area, it is always classed as EF0. An EF5 tornado has winds over 200 MPH (322 KPH) and can totally destroy reinforced concrete structures, even throwing rail cars a considerable distance.
This was the deadliest tornado recorded in Oklahoma since an F5 tornado killed 107 people in Woodward on April 9, 1947. It was also the deadliest tornado ever recorded in the Oklahoma City metropolitan area; the previous record was held by an F4 tornado that affected southwestern portions of the city on June 12, 1942, killing 31 people and causing $500,000 in damage ($ million in (2022 USD) when adjusted for inflation). It was the costliest tornado in US history until an EF4 tornado hit Tuscaloosa and northern portions of Birmingham, Alabama on April 27, 2011, causing an estimated $2.45 billion in damage (, the Bridge Creek–Moore tornado is the fourth-costliest tornado, having been surpassed by the EF5 tornadoes that hit Joplin on May 22, 2011, and areas of Moore near the 1999 storm track on May 20, 2013). National Weather Service researchers estimated that the death toll from the storm would likely have exceeded 600 had it not been for the advanced warning through local television and radio stations and exercising proper safety precautions.
Since 1850, only seven tropical cyclones have brought gale-force winds to the Southwestern United States. They are: The 1858 San Diego hurricane that was reconstructed as just missing landfall in 1858, the 1939 Long Beach tropical storm that made landfall near San Pedro in 1939, the remnants of Tropical Storm Jennifer-Katherine in 1963, the remnants of Hurricane Emily in 1965, the remnants of Hurricane Joanne in 1972, the remnants of Hurricane Kathleen in 1976, and Hurricane Nora in 1997, after it was downgraded to a tropical storm.
In total, this tornado killed 72 people, all in Alabama. This made it the deadliest single tornado ever to strike the state of Alabama as well as (at the time) the deadliest in the United States since the 1955 Udall, Kansas tornado that killed 80 people. This death toll would go on to be exceeded by the Joplin EF5 tornado less than a month later. Damage from the tornado amounted to $1.29 billion, making this one of the costliest tornadoes in U.S. history. This tornado also had the longest track of any tornado in the outbreak, with its path extending across Northern Alabama and into Tennessee.
On May 22, a large, devastating EF5 tornado tracked through Joplin, Missouri, leaving behind catastrophic damage. It was a multiple-vortex tornado in excess of wide. Mainly the southern part of the city was affected with most structures in the area either damaged or destroyed. 162 people were killed along the path through Jasper and Newton counties in Missouri, making it the deadliest U.S. tornado since 1947, and one of the deadliest single tornadoes ever recorded. Among the most heavily damaged structures was St. John's Hospital (pictured right), which later was torn down due to the severity of the structural damage. Damages were estimated at around $2.8 billion (2011 USD).
Though Andrew was a small tropical cyclone for most of its lifespan, it caused extreme damage, especially in the Bahamas, Florida, and Louisiana. The vast majority of the damage was as a result of extremely high winds, although a few tornadoes spawned by Andrew caused considerable damage in Louisiana. Throughout the areas affected, almost 177,000 people were left homeless. Outside of the Bahamas, Florida, and Louisiana, effects were widespread, although damage was minimal. Overall, $27.3 billion in losses and 65 fatalities were attributed to Andrew, with some estimates ranging as high as $34 billion. Andrew was the costliest hurricane in U.S. history at the time, but is now seventh following hurricanes Katrina (2005), Ike (2008), Sandy (2012), Harvey (2017), Irma (2017), and Maria (2017).
While direct measurement of the most violent tornado wind speeds is nearly impossible, since conventional anemometers would be destroyed by the intense winds and flying debris, some tornadoes have been scanned by mobile Doppler radar units, which can provide a good estimate of the tornado's winds. The highest wind speed ever measured in a tornado, which is also the highest wind speed ever recorded on the planet, is 301 ± 20 mph (484 ± 32 km/h) in the F5 Bridge Creek-Moore, Oklahoma, tornado which killed 36 people. Though the reading was taken about above the ground, this is a testament to the power of the strongest tornadoes.
There were no building codes requiring tornado shelters nor specifically designed to prevent tornado damage until the 2011 Joplin tornado prompted a local ordinance requiring hurricane ties or similar fasteners. The state of Oklahoma adopted the minimum U.S. standard that year for the first time, but did not add high-wind protections like those in Florida designed to protect against hurricanes. Other states in Tornado Alley have no statewide building codes. The chance of any given location in Tornado Alley getting hit by an F-2 tornado (strong enough to do major structural damage and exceeding the 90 mph guideline for straightline winds) is about 1 every 4,000-5,000 years; in other areas the annual probability is one in several million. The most stringent building codes only require earthquake strengthening for a 1 in every 500-1,000 year probability.
Throughout the season, many typhoons made landfall at a higher intensity. Typhoon Saomai was the most powerful typhoon to strike China for over 50 years, as a Category 4 typhoon, responsible for over 400 deaths. Typhoon Shanshan struck Japan and became the costliest typhoon this season with a total damage of about $2.5 billion. The Philippines got hit by a total of six typhoons, which saw the highest number since 1974. All six typhoons were responsible for over 1,000 casualties and several millions of damages. Typhoon Ioke, which formed from the Central Pacific, entered the basin and became the strongest Central Pacific hurricane. Moreover, it was stated that the ratio of intense typhoons was 0.73, which was the highest since 1970.
In South America, a phenomenon known as the El Nino Oscillation Cycle, between floods and drought on the Pacific Coast has made as much as a 35% difference in Global yields of wheat and grain.
161 people were killed and at least 990 injured when an EF5 multiple-vortex tornado hit Joplin, Missouri. Because Joplin is located in a tornado-heavy area of the country, many people considered the tornado sirens routine and ignored them. Instead, many residents waited until they received confirmation from another, non-routine, source, such as seeing the tornado, a radio or TV report, or hearing a second siren. In the aftermath, an assessment team recommended that emergency warnings take risk perception into account to convey a sense of urgency. NOAA Officials are considering ways to change the warning system to distinguish smaller tornadoes from more deadly ones.
The tropical cyclones of the season produced a total of 88 fatalities and $38.5 million in property damage (1950 USD). The first officially named Atlantic hurricane was Hurricane Able, which formed on August 12, brushed the North Carolina coastline, and later moved across Atlantic Canada. The strongest hurricane of the season, Hurricane Dog, reached the equivalent of a Category 4 hurricane on the Saffir–Simpson scale, and caused extensive damage to the Leeward Islands. Two major hurricanes affected Florida: Easy produced the highest 24-hour rainfall total recorded in the United States, while King struck downtown Miami as a Category 4 hurricane and caused $27.75 million (1950 USD) of damage. The two major landfalls made the 1945–1950 period the only five-year period to feature five major hurricane landfalls in the United States—a record that held until tied in 2000–2005. The last storm of the year, an unnamed tropical storm, dissipated on November 13.
The 2000 Pacific hurricane season was an above-average Pacific hurricane season, although most of the storms were weak and short-lived. There were few notable storms this year. Tropical Storms Miriam, Norman, and Rosa all made landfall in Mexico with minimal impact. Hurricane Daniel briefly threatened the U.S. state of Hawaii while weakening. Hurricane Carlotta was the strongest storm of the year and the second-strongest June hurricane in recorded history. Carlotta killed 18 people when it sank a freighter. Overall, the season was significantly more active than the previous season, with 19 tropical storms. In addition, six hurricanes developed. Furthermore, there were total of two major hurricanes, Category 3 or greater on the Saffir–Simpson hurricane wind scale.
The Netherlands has the highest average number of recorded tornadoes per area of any country in the world (more than 20, or 0.0005 per km), annually), followed by the UK (around 33, or 0.0001 per km), per year), but most are small and cause minor damage. In absolute number of events, ignoring area, the UK experiences more tornadoes than any other European country, excluding waterspouts. Europe uses its own tornado scale, known as the TORRO scale, which ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes.
More tornadoes occur in Texas than in any other US state. The state which has the highest number of tornadoes per unit area is Florida, although most of the tornadoes in Florida are weak tornadoes of EF0 or EF1 intensity. A number of Florida's tornadoes occur along the edge of hurricanes that strike the state. The state with the highest number of strong tornadoes per unit area is Oklahoma. The neighboring state of Kansas is also a particularly notorious tornado state. It records the most EF4 and EF5 tornadoes in the country.
The United Kingdom has the highest incidence of tornadoes, measured by unit area of land, than any other country in the world. Unsettled conditions and weather fronts transverse the Islands at all times of the years and are responsible for spawning the tornadoes, which consequently form at all times of the year. The United Kingdom has at least 34 tornadoes per year and possibly as many as 50, more than any other country in the world relative to its land area. Most tornadoes in the United Kingdom are weak, but they are occasionally destructive. For example, the Birmingham tornado of 2005 and the London tornado of 2006 both registered F2 on the Fujita scale and both caused significant damage and injury.
It is internationally recognised that the United Kingdom has a higher incidence of tornadoes, measured by unit area of land, than any other country in the world. Dr T. Theodore Fujita (inventor of the Fujita scale), an American meteorologist, was the first to recognise the UK as the top site for tornadoes in 1973. The United Kingdom has at least 33 tornadoes per year, more than any other country in the world relative to its land area. Although most tornadoes are weak, there are occasional destructive events, for example, the Birmingham tornado of 2005 and the London tornado of 2006. Both registered F2 on the Fujita scale and both caused significant damage and injury. The largest ever recorded was thought to have been an F4, again in London in 1091. The most deadly occurred on 28 December 1879. All 74 lives were lost when a passenger train plunged from the Tay Bridge (Tayside) into the Tay Estuary, when the middle section of the bridge collapsed. Although the bridge was poorly constructed and had already been weakened in earlier gales (including the pre-existing winds at the time of the tragedy), the ultimate failure is believed to have been caused by two or three waterspouts which were sighted close to the bridge immediately before the accident. A tornado also developed in London on 3 July 2007.
The UK also holds the title for the highest known 'outbreak' of tornadoes outside of the United States. The largest tornado outbreak in Britain is also the largest tornado outbreak known anywhere in Europe. On 23 November 1981, 105 tornadoes were spawned by a cold front in the space of 5.25 hours. Excepting Derbyshire, every county in a triangular area from Gwynedd to Humberside to Essex was hit by at least one tornado, while Norfolk was hit by at least 13. Very fortunately most tornadoes were short-lived and also weak (the strongest was around T5 on the TORRO Tornado Scale) and no deaths occurred.