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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan <br />Volume 2 — Hazard Inventory <br />4.3.2C) shows the tornado reports nationally from 1950-2014. You can see in the chart that tornadoes <br />occur (and are reported) more typically starting in April through September with the greatest months <br />being June and July. These two months are typically identified as Minnesota's tornado season. <br />GRAPHIC 4.3.2C <br />700 <br />600 <br />500 <br />Va <br />.4..a <br />c> 400 <br />n <br />Oj <br />300 <br />4t <br />Number of Tornado Reports Per.....Moil 1950 .....2014 <br />Row) IDa�ta, National Chrna�ft IDa�ta CerAer, IMIN 1DNIR 201.4� <br />200 <br />100 <br />0 <br />lan Feb IMar Afar May .1 un Dull Aug Sep OCL NOv IDec <br />Month <br />4.3.2.7. Historical Data/previous occurrence Bld <br />Native peoples in tornado -prone areas such as Hennepin County experienced tornadoes and developed <br />oral traditions to explain them. The first written record of an American tornado is from July 8, 1680, in <br />Cambridge, MA. The first officially recorded tornado in Minnesota was sighted near Fort Snelling in <br />Hennepin County on April 19, 1820. Because tornadoes are more numerous in the United States than any <br />other nation, tornadoes have been studied here more than anywhere else. In 1882, the U.S. Army Signal <br />Corps assigned Sgt. John Finley to investigate weather conditions that form tornadoes. Technology limits <br />made the early understanding of tornado anatomy difficult. The adoption of radar revolutionized the <br />study and forecasting of tornadoes. The first US Weather Bureau radar in Minnesota was installed at the <br />Minneapolis -Saint Paul International Airport in the early 1960s. Air Force meteorologists issued the first <br />tornado forecast in March 1948. The US Weather Bureau followed suit by 1952. Important advancements <br />in understanding tornadoes were made by Theodore Fujita who studied tornado formation and damage <br />across the Midwest in the 1960s and 70s. Modern era radar was installed at the Twin Cities office of the <br />National Weather Service in 1996. <br />In Minnesota and Hennepin County, the record of tornado sightings encompasses nearly 200 years from <br />records kept at Fort Snelling. The local newspaper record, which often contain notices of weather events, <br />goes back over 160 years. In general, early reports are incomplete and may contain some factual errors. <br />75 <br />