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In 2009, tornadic activity was generally near average. Each year, tornadoes and tornado outbreaks occur worldwide primarily under conductive conditions, though a majority of tornadoes form in the United States. Tornadoes also occur to a less frequent extent in Europe, Asia, and Australia. In the U.S., there were 1,304 reports of tornadoes received by the Storm Prediction Center (SPC), and 1,156 tornadoes were confirmed to have taken place. Worldwide, 44 fatalities were caused by tornadoes, with 21 in the U.S., 15 in India, four in Canada, two in Greece and one each in Serbia and Russia. Tornadic activity in 2009 began with the development an EF1 tornado near Stringer, Mississippi on January 3 and ended with the dissipation of an EF0 tornado near Vancleave, Mississippi on December 24. During the year the two strongest tornadoes were both assessed as an EF4 – one occurred in Oklahoma on February 10 and the second occurred in Tennessee on April 10. During the early months of the year tornadic activity remained mostly below average in contrast to am active trend of tornadoes in 2008. Activity peaked in April and May as a result of destabilizing atmospheric conditions and featured a bulk of the year's tornadoes. However, the number of developing tornadoes subsequently began to wane and remained generally inactive for the latter half of 2009. ==Synopsis== In contrast to the first nine months of 2008, the final quarter was fairly inactive overall, and the inactivity continued into January 2009 with only a few tornadoes in the US the entire month as generally stable air dominated. The pattern broke for the first time on February 10 when a modest tornado outbreak occurred, but produced a deadly tornado in Oklahoma. The severe weather activity changed to a moderate pace for the remainder of February into March, and although the start of the season did not have a large prolific tornado outbreak, it has had several notable events. Overall activity in March ran near normal. The start of Easter weekend brought the first large outbreak of 2009, with many tornadoes on both April 9 and 10. Steady activity through the remainder of April sent the month above average. May started quite active, but in a rather unusual pattern as most tornadoes in the early part of the month were due to summer-like derechos as opposed to large-scale supercells. The second half of May was unusually quiet, with few significant severe weather events. June saw activity return to an above normal pace, and the middle part of the month was particularly active. However, most of the tornadoes were in open country, and activity was steady over many days as opposed to a large outbreak. The second half of 2009, overall, was not active. July also ran near normal, but August ran below normal with most of the activity concentrated in a single non-tropical outbreak. Without any landfalling tropical cyclones in the Atlantic and a relatively stable air mass, September was extremely quiet with only a very small number of isolated weak tornadoes. While October was near average tornado-wise, activity stabilized greatly again in November and it produced only three tornadoes, one of the least active months in recent years. December was more active, primarily as a result of a moderate outbreak just before Christmas. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Tornadoes of 2009」の詳細全文を読む スポンサード リンク
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