Instruct: Given a question, retrieve documents that can help answer the question.
Query: How big can tornados get?
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.
The United States averaged 1,274 tornadoes per year in the last decade while Canada reports nearly 100 annually (largely in the southern regions). However, the UK has most tornadoes per area per year, 0.14 per 1000 km², although these tornadoes are generally weak, and many other European countries have a similar number of tornadoes per area.
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.
Often people try to avoid or outrun a tornado in a vehicle. Although cars can travel faster than the average tornado, the directive from the National Weather Service is for house-dwellers in the path of a tornado to take shelter at home rather than risk an escape by vehicle. This is a result of several factors and statistics. An interior room inside a well-built frame house (especially one with a basement) provides a reasonable degree of protection from all but the most violent tornadoes. Underground or above-ground tornado shelters, as well as extremely strong structures such as bank vaults, offer almost complete protection. Cars, on the other hand, can be heavily damaged by even weak tornadoes, and in violent tornadoes they can be thrown large distances, even into buildings. High-profile vehicles such as buses and tractor trailers are even more vulnerable to high winds.
The United States averaged 1,274 tornadoes per year in the last decade. April 2011 saw the most tornadoes ever recorded for any month in the US National Weather Service's history, 875; the previous record was 542 in one month. It has more tornadoes yearly than any other country and reports more violent (F4 and F5) tornadoes than anywhere else.
The tornado initially touched down just east of the Missouri-Kansas state line near the end of 32nd Street at 5:34 pm CDT (22:34 UTC) and tracked due east, downing a few trees at EF0 intensity. Eyewitnesses and storm chasers reported multiple vortices rotating around the parent circulation in that area. Civil defense sirens sounded in Joplin 20 minutes before the tornado struck in response to a tornado warning issued by the National Weather Service, but many Joplin residents didn't heed them. The tornado strengthened to EF1 intensity as it continued through rural areas towards Joplin, snapping trees and power poles and damaging outbuildings. Widening, the tornado then tracked into the more densely populated southwest corner of the city near the Twin Hills Country Club. It heavily damaged several homes at a subdivision in this area at EF1 to EF2 strength. The tornado continued to strengthen as it ripped through another subdivision just east of Iron Gates Rd. Numerous homes were destroyed at EF2 to EF3 strength at that location, and multiple vehicles were tossed around, some of which were thrown on or rolled into homes.
The now massive wedge tornado then crossed S. Schifferdecker Ave., producing its first area of EF4 damage as several small but well-built commercial buildings were flattened. Consistent EF4 to EF5 damage was noted east of S Schifferdecker Ave and continued through most of southern Joplin. Numerous homes, businesses, and medical buildings were flattened in this area, with concrete walls collapsed and crushed into the foundations. A large steel-reinforced step and floor structure leading to a completely destroyed medical building was "deflected upward several inches and cracked". Steel trusses from some of the buildings were "rolled up like paper", and deformation/twisting of the main support beams was noted. Multiple vehicles were thrown and mangled or wrapped around trees nearby. Several 300-pound concrete parking stops anchored with rebar were torn from a parking lot in this area and were thrown up to 60 yards away. Iowa State University wind engineer Parka Sarkar was able to calculate the force needed to remove the parking stops and found that winds exceeding 200 mph were needed to tear them from the parking lot.
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.
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.
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.
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 United States averages about 1,200 tornadoes per year, followed by Canada, averaging 62 reported per year. NOAA's has a higher average 100 per year in Canada. The Netherlands has the highest average number of recorded tornadoes per area of any country (more than 20, or 0.0013 per sq mi (0.00048 per km), annually), followed by the UK (around 33, or 0.00035 per sq mi (0.00013 per km), per year), although those are of lower intensity, briefer and cause minor damage.
Tornadoes kill an average of 179 people per year in Bangladesh, the most in the world. Reasons for this include the region's high population density, poor construction quality, and lack of tornado safety knowledge. Other areas of the world that have frequent tornadoes include South Africa, the La Plata Basin area, portions of Europe, Australia and New Zealand, and far eastern Asia.
The average tornado usually only stays on ground for 5 minutes but these figures, reported by the National Climatic Data Center for the period between 1991 and 2010, show the seventeen U.S. states with the highest average number of tornadoes per per year.
After the U.S., Canada gets the most tornadoes in the world. The average number of tornadoes per is highest in the southern parts of Alberta, Saskatchewan, and Manitoba, as well as Southern Ontario. Northern Ontario between the Manitoba border and the Lake Superior lakehead is also prone to severe tornadoes, but tornadoes in this area are believed to be underestimated due to the extremely low population in this region.
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.
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).
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 term was first used in 1952 as the title of a research project to study severe weather in areas of Texas, Oklahoma, Kansas, South Dakota, Iowa, Missouri, Nebraska, Colorado, North Dakota, and Minnesota. It is largely a media-driven term although tornado climatologists distinguish peaks in activity in certain areas and storm chasers have long recognized the Great Plains tornado belt.
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.
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.
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.
The 2011 Joplin tornado was a catastrophic EF5-rated multiple-vortex tornado that struck Joplin, Missouri, late in the afternoon of Sunday, May 22, 2011. It was part of a larger late-May tornado outbreak and reached a maximum width of nearly during its path through the southern part of the city. This particular tornado was unusual in that it intensified in strength and grew larger in size at a very fast rate. The tornado tracked eastward across the city, and then continued eastward across Interstate 44 into rural portions of Jasper County and Newton County. It was the third tornado to strike Joplin since May 1971.
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.
Recent exhibitions at Tensta konsthall include
• “Abstract Possible: The Stockholm Synergies,” with Doug Ashford, Claire Barclay, Goldin+Senneby, Wade Guyton, Mai-Thu Perret, Walid Raad, and Haegue Yang, among others
• “Kami, Khokha, Bert and Ernie: World Heritage” by Hinrich Sachs
• “Doing what you want: Marie-Louise Ekman accompanied by Sister Corita Kent, Mladen Stilinović, and Martha Wilson” 
• “The Society without qualities” with Sören Andreasen, Ane Hjort Guttu, Sture Johannesson, Sharon Lockhardt, and Palle Nielsen (part of “The new model” and curated by Lars Bang Larsen)
• “Working With…” by Zak Kyes
• “We are continuing BBDG” with Bernd Krauss
• “Two Archives” by Babak Afrassiabi and Nasrin Tabatabai
The tornado's unusual behavior consisted of these simultaneous occurrences: abrupt changes in direction, rapid enlargement to a width of in diameter in about 30 seconds, swift increase in forward motion from about within a few minutes, multiple vortices within and around, and an expansive translucent outer circulation without a full condensation funnel while being surrounded and obscured by precipitation made it a worst-case scenario for storm chasers. Several professional and amateur chasers were caught off guard and impacted by the tornado. Many were located in a region northeast of the tornado, known as the "bear's cage". Chasers can generally get a clear view of the tornado from that area; however, it places them at great risk and with little time to react should the storm take a left turn.
Winfield Toll Bridge, also known as the Ross Booth Memorial Bridge, is a historic three-span cantilever Warren Truss bridge located at Winfield and Red House, Putnam County, West Virginia. It was built in 1955, and spans the Kanawha River, carrying West Virginia Route 34. The cantilever through-truss consists of two anchor spans each 245 feet in length and the main span 462 feet in length between pier center lines. The main span consists of two 128 feet, 4 inch, cantilever arms and a 205 feet, 4 inch, suspended span.
A tornado is a rotating, funnel-shaped cloud that extends from a thunderstorm to the ground with whirling winds that can reach 300 miles per hour. Although the weather channel can sometimes attempt to predict when an tornado will hit and where, sometimes they occur with little or no time for a warning to be given. Generally tornadoes occur near the trailing end of a thunderstorm and can sometimes be seen forming. It is a common misconception that tornadoes only occur in areas like Tornado Alley, however they have been observed on every continent except Antarctica. Since Tornadoes have the ability to strike quickly with no warning and cause extreme devastation American universities are learning to be aware of their vulnerability and risk. All Universities prepare for the worse even if tornadoes do not typically happen in their vicinity.