Minnesota tornado climatogy refers to the historical occurances and trends of tornadoes in the U.S. state of Minnesota.. The state lies along the northernern border of the U.S. in the central United States. This area is commonly referred to as Tornado Alley, the place where violent tornadoes occur with more regularity than anywhere else on earth.
On average 26 tornadoes are reported to touch down in Minnesota per year since 1950. However, the actual number of touch downs is likely higher than this, given increase in tornado detecting techonology and storm spotting networks in recent years. The majority of tornadoes touch down between 3:00 pm - 7:00 pm, and 98% of the tornadoes are rated at F3 or lower. The southern half of the state receives roughly 70% of the tornadoes.
Time of year edit
Early season edit
No tornadoes have ever been recorded in Minnesota during the winter months of December, January or February. Though tornadoes have occurred in the neighboring states of Iowa and Wisconsin during this time, the lack of sufficient heat and moisture over Minnesota during these months is almost never conducive for tornado, or even thunderstorm development. Historically Minnesota's "tornado season" begins in March,[1] with the earliest tornado from a seasonal standpoint occurring on March 18, 1968 near Truman, Minnesota. Only 21 tornadoes have been confirmed in Minnesota's history during the month of March; 14 of which touched down during the 1998 Comfrey – St. Peter tornado outbreak on March 29, 1998.
Tornadic activity remains relatively low in April, with this month seeing just 5% of the state's annual tornadoes. This is especially true in the first half of April. From 1950-1997, Minnesota experienced 61 tornadoes in the month of April, with just seven of those occurring from April 1–April15.[2]
Even though the state averages only about one tornado a year during April, strong storms can occur. The 1886 Sauk Rapids tornado devastated central Minnesota on April 14, 1886. It was approximated at F4 strength and killed 72 people, making it Minnesota's deadliest tornado on record. A strong April tornado outbreak occurred on April 5, 1929, when one F3 and three F4 tornadoes touched down in East-Central Minnesota.[3] One of the F4 tornadoes touched down near Lake Minnetonka, and stayed on the ground nearly 80 miles, moving through the communities of Columbia Heights, Fridley, Forest Lake and Chicago City, before crossing the St. Croix River and eventually ending near Millford, Wisconsin. This tornado killed two people, injured 40 others, and caused nearly $1 million in property damage (1929 USD).[4]
Peak edit
As the middle of spring approaches, heat and humidity begin to increase dramatically over the southern part of Minnesota, leading to more numerous thunderstorms and tornadoes. The state goes from an average of 1.2 tornadoes per year in April to 4.1 in May. During June and July, Minnesota receives regular influxes of heat and humidity, but unlike states like Oklahoma that are very dry during the summer months, Minnesota is in a climatologically favorable location for thunderstorms and tornadoes. The polar jet stream is often present over or near Minnesota, which allowed cool air often present over Canada to frequently clash with the warm and humid air, sparking off frequent thunderstorms.
June and July are the peak months for tornado activity in Minnesota, with these two months accounting for 60% of the total tornadoes in the state. Tornado activity starts to lull in late July and early August, but hits a secondary peak in middle to late August as the polar jet stream once against begins to strengthen. Two of Minnesota's strongest and deadliest tornadoes occurred in late August: The 1883 Rochester tornado which occurred on August 21 and killed 37, and the 1918 Tyler tornado, which also occurred on August 21 and killed 36 people.
Late season edit
As the warm air retreats to the south, and cold, dry air from Canada takes hold over Minnesota, the number of tornadoes falls off dramatically during the autumn months, and historically Minnesota's tornado season ends in November. One active late season outbreak occurred on October 26, 1996 when 14 tornadoes touched down in the state. This was the most active tornadic day during the month of October in the state's history. Since 1950 however, the state has recorded just 27 total tornadoes during the moth of October. The month of November has seen just 5 tornadoes in the state, and the latest tornado from a seasonal standpoint ever recorded in Minnesota on November 16, 1931 near Maple Plain.
Time of day edit
Tornadoes in Minnesota can occur at all hours of the day, but most occur during the late afternoon hours. According to several studies, just over one-third of tornadoes strike between the hours of 4:00 pm – 6:00 pm, when daytime heating is most prevalent. During the summer when there is increased sunlight, tornadoes become more common into the early evening hours.[5]
Geography edit
The majority of the tornadoes in the state occur in the south, with around 70% of tornadoes occurring in the southern half ot the state.
Fatalities edit
Fatalities from tornadoes in Minnesota have become increasingly rare as techonolgy and storm awareness have increased. Official statistics for torndaoes were not kept before 1950, but records are available for major events. The deadliest tornado in Minnesota's history occurred on April 14, 1886 when 72 people died in the towns of St. Cloud, Sauk Rapids and Rice. The second deadliest tornado hit Fergus Falls on June 19, 1922, killing 59 people. Other major fatality storms include 37 people in Rochester on August 21, 1883, and 36 people in Tyler on August 21, 1918.
However, as awareness and technology have increased, tornado fatalities have dropped. The last tornado in the state to kill more than 10 people was on 1946 in Mankata and North Mankato. The last tornado to cause more than one falatiy was near Little Fork, when two peopled died on ___, 1993. Since 2000, tornados have killed just _ people in the state, with the most recent being on May 25, 2008 in Hugo during the Late May 2008 tornado outbreak sequence.
Records edit
The largest single day tornado outbreak was on June 16, 1992 when 27 tornadoes touched down across the state. The most active month for tornadoes was June of 2001, and the most active year was 2001 was 72 tornadoes were recorded.
The deadliest tornado was in Sauk Rapids in 1886. The strongest were two F5 tornadoes that occurred near Tracy in 1968 and Chandler on June 16, 1992.
The most damaging tornado outbreak in terms of dollars was on May 6, 1965 when six strong tornadoes touched down in and near the Twin Cities metro area.
References edit
- ^ http://www.mnsu.edu/security/emergencies/severe/safety.html
- ^ http://www.tornadohistoryproject.com/tornado.php?yr=%25&mo=4&day=%25&st=Minnesota&fu=%25&co=Any&l=auto&submit=Table&ddat=on&dsta=on&dfuj=on&dfat=on&dinj=on&dcou=on&format=basic&p=1&s=1
- ^ http://www.crh.noaa.gov/mpx/?n=1998mar29historical
- ^ Seeley, Mark (2006). Minnesota Weather Alamanac. Minnesota Historical Society Press. p. 182. ISBN 0-87351-554-4.
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