Tornadoes in the United States
The Great Plains, the Midwest, the Mississippi Valley and the southern United States are all areas that are vulnerable to tornadoes.
Another highly significant region – colloquially known as Dixie Alley – is the southern United States and particularly the northern and central parts of Alabama and Mississippi.
During the winter months, tornadoes are usually spotted in the Southern area of the country, as well as states near the Gulf of Mexico.
[11] This is due to cold air moving southward reaching its southern limit of expansion, and stopping over the Gulf Coast.
[11] As spring passes and summer begins, the mass of warm moist air moves northwest into the Great Plains and Midwestern states.
[11] During the late summer and early fall months, tornado activity in the United States tapers off.
"[21] Some states in the area that may be hit by tornadoes frequently include Oklahoma, Kansas, Illinois, Indiana, and Iowa.
[11] The frequency begins to decrease in the middle of the summer, as the air mass moves northward into the Great Lakes states.
The tornado apparently strengthened as it neared Northwood, and at 9:38 pm CDT (0238 UTC), storm chasers reported that it had grown to over 1⁄2 mile (0.8 km) in diameter.
[22] Several satellite tornadoes were observed as the very large wedge approached the town of Greensburg, Kansas.
It was an estimated 1.7 miles (2.7 km) in diameter and was later confirmed to have been an EF5 on the Enhanced Fujita Scale (the highest possible rating).
[27] Some areas experience repeated damaging tornado events, such as the Tennessee Valley and in northern Alabama.
[28] For the period 1950 to 2006, three hundred and fifty eight people were killed by tornadoes in Alabama, ranking the state third nationwide behind Texas (521) and neighboring Mississippi (404).
NCDC figures for the period 1950 to 2006 show that Pennsylvania reported 697 tornadoes, followed by New York State (358), Maryland (269), Massachusetts (153), New Jersey (144), Maine (101), New Hampshire (86), Connecticut (82), Delaware (58), Vermont (37), Rhode Island (9), and the District of Columbia (1).
[32] Florida's most violent tornadoes generally occur during the winter months, when the state is most vulnerable to invasions of cold air that help generate such storms.
Eastern Colorado, both climatically and physically, has much more in common with the neighboring Plains states of Kansas and Nebraska than with the mountainous areas further west.
Small cities such as Limon, Kit Carson, Thurman, and Flagler are some places in Eastern Colorado that have experienced dangerous tornadoes.
[36] Of the states in this region – according to NCDC figures for the 1950 to 2006 period – Colorado reported 1,617 tornadoes, followed by Wyoming with 560, Montana (345), Idaho (175), and Utah (114).
[15] New Mexico borders the notoriously tornado prone states of Texas and Oklahoma, hence the noticeably higher figures.
New Mexico's region and the desert landscape of the state help prevent the amount of twisters that happen in Oklahoma and Texas.
[41] However, these high-intensity storms do account for an average of seventy percent of all tornado-related deaths in the United States each year.
From 1950–1970 tornadoes were assessed retrogressively, primarily using information recorded in government databases, and newspaper photographs and descriptions.
[45] The strong F5 storm took place near the town of Bridge Creek, Oklahoma, located in Grady County.
[45] Other scientists reviewed the DOW data taken by the students, and concluded that the estimated wind speed may have been inaccurate, but still over 300 miles per hour (130 m/s).
[47] Kentucky was followed by Indiana (13), Illinois (9), Missouri and Oklahoma (6), Ohio (4), Alabama and Tennessee (3), and Florida and Kansas (1).
[48] It is a widespread myth that tornadoes are "attracted" to mobile home parks, and cause the most fatalities there because they hit there the most.
[48] An example to confirm this occurred in April 1991, when a very powerful tornado struck the town of Andover, Kansas.
When the town was hit, eighty-four homes and fourteen businesses were destroyed by the tornado, but with no fatalities and only minor injuries.
An EF0 tornado has estimated wind speeds from 65–85 mph (29–38 m/s; 105–137 km/h) which usually results in minor structural damage and broken tree limbs.
An EF5 tornado has estimated wind speeds of greater than 200 mph (89 m/s; 320 km/h) and can destroy reinforced concrete structures and well-built homes, reducing them to piles of rubble or sweeping them entirely off their foundations or slabs.
