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1998 Comfrey–St. Peter tornado outbreak

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1998 Comfrey–St. Peter tornado outbreak
A house blown off its foundation near Hanska, Minnesota
Duration4 hours
Tornadoes
confirmed		16
Max. rating1F4 tornado
Fatalities2
Damage$235 million
Areas affectedSouthern Minnesota, western Wisconsin
1Most severe tornado damage; see Fujita scale

The 1998 Comfrey–St. Peter tornado outbreak was an unseasonably strong tornado outbreak which affected southern Minnesota and western Wisconsin on March 29, 1998. A strong area of low pressure combined with a warm front and favorable upper level dynamics combined to produce sixteen tornadoes over the region. Thirteen of the tornadoes were caused by one parent supercell which traveled approximately 150 miles (241 km) across southern Minnesota during the afternoon hours. Most of the destruction from this outbreak was caused by an F4 tornado that hit the town of Comfrey, Minnesota, an F3 tornado that hit St. Peter, Minnesota, and an F2 tornado that hit Le Center, Minnesota. Over $235 million in damages was reported, two people were killed, and 36 people were injured. Gustavus Adolphus College in St. Peter was especially hard hit, with several buildings destroyed, thousands of trees lost, and nearly 80% of the windows on the campus shattered. In Comfrey, 75% of the structures in the town were damaged or destroyed, including the school. Seven counties in southern Minnesota were declared federal disaster areas.

This outbreak broke many early–season tornado records for the state of Minnesota. The fourteen tornadoes recorded were the most to ever touch down in one day during the month of March. The F4 tornado was the strongest ever recorded in March, and its 67 mile (108 km) path is the longest continuous–track tornado recorded in Minnesota during any month. This event was named the top severe weather event in Minnesota during the 1990s by Metro Skywarn, the Twin Cities branch of the Skywarn weather spotter network. The following December, the Twin Cities office of the National Weather Service was awarded a Bronze Medal by the United States Department of Commerce for providing excellent service to the public during the event.

Meteorological synopsis

Surface map of the upper Midwest on March 29, 1998 at 2100 UTC

The driving force behind this tornado outbreak was a strong surface area of low pressure stationed over the western high plains. On the morning of March 29 the 993 mb low was centered over eastern Wyoming, with a warm front stretching eastward across Nebraska and Iowa.[1] An upper level trough of low pressure was centered over the southwestern United States, which caused an upper level jet stream with winds of 100 knots (190 km/h) to push towards Minnesota from the southwest. A low level jet from the south with winds of 50 knots (93 km/h) transported a plume of moisture into the region, helping to push temperatures into the lower 70s °F (23 °C) and dew points into the middle 60s °F (18 °C).[1] Winds on the surface were from the southeast, which helped to enhance the potential for tornadoes.[2]

By early afternoon, the low pressure area had moved east into Nebraska, and the warm front had pushed northward into southern Minnesota.[1] The atmosphere to the south of the warm front was strongly capped, meaning that the best chance of thunderstorm development was along, and just north of the warm front.[3] By the time the thunderstorms started developing, CAPE values (a measurement for the level of tropospheric instability) were 2000 J/kg. Low level and deep layer shear values of 44 knots (81 km/h) and 87 knots (161 km/h) were present over the same areas. The strong upper level jet, CAPE and shear values combined to create very favorable conditions for the development of severe thunderstorms and tornadoes.[1]

Forecasts

The SPC Day 1 severe weather outlook on March 29, 1998

Weather forecasters first began to notice the severity of impending weather situation after the 00 UTC computer model runs on the night of Friday, March 27.[3] On Saturday, March 28 at 1730 UTC the Storm Prediction Center issued a Day 2 moderate risk of severe weather for southeast Minnesota, northeast Iowa, northwest Illinois and much of Wisconsin.[4] Later model runs on March 28 only increased forecasters confidence that a major severe weather event would occur the following day.[3]

Early on Sunday March 29, forecasters at the Twin Cities NWS noticed that due to the models prediction of strong wind shear and instability, the tornado risk was quite high for their region. Area forecast discussions early on March 29 mentioned the possibility of F3–strength tornadoes later in the day.[3] Also on the morning of March 29, the Storm Prediction Center issued a Day 1 moderate risk of severe weather. This moderate risk area was more narrow than the previous days outlook, encompassing only southwest Wisconsin, northern Iowa and the southern third of Minnesota.[1]

As the day moved on, the Twin Cities, Sioux Falls and La Crosse NWS forecast offices all saw the potential for "strong to violent" tornadoes, and used such verbiage in their forecasts.[1] The Twin Cities NWS noted in their 1826 UTC forecast discussion that "thunderstorms located south of a Redwood Falls to Minneapolis to Rice Lake line could be particularly strong with the potential of tornadic thunderstorms".[3] Just before 1800 UTC, the Storm Prediction Center issued a mesoscale discussion stating: "Given strength of vertical shear profiles, CAPE on the order of 2000 J/kg will support increasing potential for tornadic supercells during the afternoon hours, especially along an axis roughly from Yankton through Sioux Falls into Redwood Falls and Minneapolis/Rochester areas. We will continue to monitor. Present indications are WW (Weather Watch) will be necessary within the next 2 to 3 hours.". At 1:35 pm the Storm Prediction Center issued tornado watch #132 with a particularly dangerous situation designation. The watch area encompassed most of southern Minnesota and northern Iowa, along with small parts of northeast Nebraska, southeast South Dakota, southwest Wisconsin, and was made in effect from 2:00 pm – 8:00 pm CST.[1]

Outbreak description

Radar image of the supercell thunderstorm as it produced an F4 tornado in Brown County, Minnesota.

The thunderstorms that would eventually go on to spawn the tornadoes began forming in southeastern South Dakota around 2:00 pm CDT. The first severe weather report of the outbreak was of 3⁄4 inch (19 mm) diameter hail two miles (3 km) south of Brandon, South Dakota.[5] Shortly thereafter the thunderstorms moved east across the border into Minnesota. After several more reports of severe hail with the growing thunderstorms,[6][7] the first tornado of the day, rated F2 on the Fujita scale, touched down at 3:23 pm two miles (3 km) north of Lismore.[8] It was on the ground for less than a mile (1.6 km) and caused minor damage. Five more tornadoes (all rated F2 or lower) briefly touched down during the next hour in the same general area; none of which inflicted major damage. All of these tornadoes were spawned by the same supercell thunderstorm. During the remainder of the afternoon hours, this supercell would proceed to track east–northeast across southern Minnesota for 150 miles (241 km), following a path slightly north of the warm front.[9]

Comfrey

Damage to a house near Comfrey

At 3:50 pm a tornado touched down seven miles (11 km) east of Avoca, Minnesota in Murray county.[10] As the tornado moved from Murray and into Cottonwood counties, it grew to a width of 900 yards (823 m) and obtained F3 strength.[11] It destroyed numerous farms, farm equipment, trees, power lines and poles, vehicles, and other structures in its path in Cottonwood County. Twenty people outside a church near Jeffers were able to get inside the church just before the tornado hit, and as a result nobody suffered serious injuries.[9][12]

At approximately 4:30 pm the twister, which witnesses described as a "mass of blowing dust" or "rolling fog bank"[9] entered Comfrey, a town of 550 people located in both Cottonwood and Brown counties. The town's fire chief saw the tornado while storm spotting and ordered the town's sirens activated.[13] The tornado moved through the center of town one minute after the sirens went off, destroying a grain elevator, the town hall and most of the main street businesses downtown.[14] The town's firehouse collapsed, and the school was heavily damaged. Fifty homes were destroyed and 100 people were left homeless.[14] Approximately 75% of the buildings in Comfrey were damaged or destroyed.[15][14]

A house in rural Brown county completely swept from its foundation

As the tornado continued to move through Brown County it achieved F4 strength and grew to 1.25 miles (2.01 km) wide.[14] Approximately 15% of the 1000 farms in Brown County sustained damage from the tornado,[16] and 500 dairy cattle were lost.[14] Northwest of Hanska a man was killed when the tornado caused his house to collapse.[14] The tornado went on to cause additional damage in Blue Earth and Watonwan counties. After traveling across six counties for 1 hour and 25 minutes and causing $75 million in damage,[11][14] the twister lifted back into the clouds at 5:15 pm four miles (6 km) southeast of Courtland.[17] In addition to the one fatality, 19 people were reported injured by this tornado.

St. Peter

A house near St. Peter removed from its foundation

At 5:18 pm, the same supercell produced another large tornado two miles (3 km) to the east of Nicollet. As the tornado moved to the east, a six year old boy was killed when he was thrown from the vehicle he was riding in.[9] At 5:30 pm the F3 tornado hit St. Peter, a town of about 10,000 people located in eastern Nicollet County, and inflicted severe damage on much of the town.[18] Gustavus Adolphus College, which sits on top of a hill on the west side of St. Peter, sustained heavy damage after taking a direct hit from the twister. Eighty percent of the windows on the campus were shattered, and most of the major buildings on campus sustained at least some damage.[19] The Chapel spire, a campus landmark, was snapped in half. The admissions office was destroyed, as was Johnson Hall, a small dormitory.[20] The tornado uprooted more than 1000 trees, almost completely denuding the campus.[15] Gustavus was on spring break at the time the tornado hit, so the campus was virtually vacant of students and there were no serious injuries or fatalities reported. Classes were canceled for three weeks afterwards, and damage at the campus was estimated at nearly $60 million.[19]

As the tornado continued through St. Peter it caused more damage and destruction. St. Peter's Catholic Church was destroyed, the hospital was severely damaged and the library was hit and lost 25% of their books.[21] Officials estimated 500 homes in St. Peter were damaged or destroyed; 1700 more were damaged and over 17,000 trees were lost.[19][22] Many of the homes and trees that were destroyed in St. Peter were more than a century old. Debris from St. Peter that was sucked into the tornado fell back down to earth as far as Rice Lake, Wisconsin, over 130 miles (209 km) away.[9] In addition to the damage in St. Peter, the tornado also damaged or destroyed 60 homes and caused $6.5 million in damage in rural areas.[21] All together this tornado was on the ground for 18 miles (29 km) and inflicted $120 million in damage.[21]

Le Center

A destroyed mobile home in LeCenter

Shortly after the St. Peter tornado dissipated, a new tornado formed at 5:48 pm two miles (3 km) north of Cleveland.[23] The half–mile (.8 km) wide tornado damaged several farms before hitting Le Center at F2 strength. The tornado damaged many businesses on the southern side of town and caused heavy damage at the Le Sueur County fairgrounds.[23] The Sunny Terrace mobile home park in Le Center took a direct hit from the tornado. Fifteen mobile homes were destroyed and another 26 were heavily damaged.[23] The manager of the mobile home park was able to alert residents to the oncoming tornado, allowing most of them to take cover in a storm shelter before the storm hit.[24] There were no fatalities from this tornado, and two people sustained injures. After traveling for 17 miles (27 km) and causing $20 million in damage, the tornado lifted from the ground one mile (1.6 km) west of the town of Montgomery.[23]

Other tornadoes

Over the next hour the supercell continued to track across southern Minnesota, dropping four more tornadoes in Rice and Dakota counties.[12] One of these tornadoes hit the town of Lonsdale at F2 strength, damaging four homes and six business in the town, and then 20 farms to the east of town. This tornado had a path of five miles (8 km) and caused $20 million in damage.[25] The last of the 13 tornadoes spawned by this supercell was a brief F0 that touched down five miles (8 km) southwest of Hastings,[26] and the supercell dissipated a few minutes later as it moved into Wisconsin.[9]

Three additional tornadoes, one in Wabasha, Minnesota and two in Wisconsin touched down this day as well. All were unrelated to the main supercell that spawned the other 13 tornadoes, and all were rated F0 on the Fujita Scale and produced only minor damage.[27][28][29]

Confirmed tornadoes

Tracks of 13 tornadoes caused by one supercell across southern Minnesota on March 29, 1998
Confirmed
Total 		Confirmed
F0 		Confirmed
F1 		Confirmed
F2 		Confirmed
F3 		Confirmed
F4 		Confirmed
F5
16 6 3 5 1 1 0


List of confirmed tornadoes - Sunday, March 29, 1998
F#
Location
County
Time (UTC)
Path length
Damage
Minnesota
F2 N of Lismore Nobles 2123 0 mi $400 thousand in damage to farm buildings and equipment
F0 E/ESE of Leota Nobles 2125 0 mi $10 thousand in damage to a few buildings.
F0 N of Wilmont Nobles 2128 0 mi $50 thousand in damage to a few buildings.
F2 NW of St. Kilian Nobles 2135 0 mi $200 thousand in damage to buildings and a tractor trailer.
F1 NE of St. Kilian Nobles 2145 0 mi $100 thousand in damage to farm buildings.
F4 Comfrey area Murray, Cottonwood, Brown, Watonwan, Blue Earth, Nicollet 2150 67 mi (107 km) 1 death. Substantial damage to the town of Comfrey and many farms across six Minnesota counties. $75 million in damages
F1 SW of Fulda Murray 2155 0 mi $50 thousand in damages to farm buildings.
F0 W of Wabasha Wabasha 2307 2 mi (3 km) None reported.
F3 St. Peter area Nicollet, Le Sueur 2318 18 mi (29 km) 1 death. $120 million in damage to the town of St. Peter, Gustavus Adolphus College heavily damaged.
F2 Le Center area Le Sueur 2348 17 mi (27 km) Southern portion of LeCenter sustains $20 million in damages.
F1 SW of Lonsdale Rice 0009 0 mi None reported.
F2 Lonsdale Rice 0016 5 mi (8 km) Homes, farms and businesses destroyed, $20 million in damages.
F2 WNW of Castle Rock Dakota 0025 3 mi (5 km) None reported.
F0 SW of Hastings Dakota 0043 1 mi (1.6 km) None reported.
Wisconsin
F0 S of Maxville Buffalo 2315 1 mi (1.6 km) None reported.
F0 NW of Tomahawk Lincoln 0128 1 mi (1.6 km) $15k in damage to sheds and garages.
Source: National Climatic Data Center[30]

Aftermath

On April 1, 1998 seven counties in Minnesota were declared federal disaster areas: Brown, Le Sueur, Nicollet, Rice, Cottonwood, Blue Earth and Nobles.[31] The federal money allowed the towns affected to cleanup the damage and begin the rebuilding process. In addition, the state of Minnesota contributed $27.6 million to the cleanup and rebuilding effort,[32] with some of that funding designated specifically for the preservation of the historical buildings in St. Peter.

Most of St. Peter's homes that were on the National Historic Register were damaged, but only one of the homes on the register had to be demolished.[33][34] The Minnesota Historical Society contributed $1.35 million to help fund the restoration of the damaged historical structures.[33] Three years after the tornado, the City of St. Peter reported that its population had grown by 2%, an unusual feat for a town that had so recently endured a natural disaster.[35]

After the tornado hit Comfrey, residents were forced to temporarily evacuate the town due to several gas leaks.[24], and the Minnesota National Guard was called in to help secure the area. As a result of the K–12 school being destroyed, students resumed classes two weeks later 20 miles (32 km) to the north in Sanborn. The school used equipment and supplies that had been salvaged from the damage, as well as items that had been donated to help stock their classrooms. Since many Comfrey residents were displaced to nearby towns, school buses from Comfrey drove to each of these towns to provide transportation to the school in Sanborn.[36] After the tornado in Comfrey there were questions on whether or not the town would survive at all; the future of the town seemed to hinge the rebuilding of the school.[37] Ultimately, most business decided to rebuild, as did the school.[38] Ground was eventually broken on a new school later in the year, and late in 1999 Comfrey celebrated the opening of their new school. Population in the town is down to 367 from the 425 it was when the tornado hit.[22]

In total, the tornadoes from this outbreak officially caused $235 million in damage,[39] although later estimates put damage at over $300 million in St. Peter alone.[22] Additionally, over $800 thousand in hail and downburst damage was reported over South Dakota, Minnesota and Wisconsin.[8] For the 13 tornadoes that touched down from the parent supercell in southern Minnesota, the Twin Cities and Sioux Falls NWS offices issued tornado warnings an average of 15 minutes before the tornadoes affected the warned areas.[4] Because of this and for excellence in forecasting the entire event, the United States Department of Commerce issued a Bronze Medal to the Twin Cities office the following December.[4]

Historical perspective

March has accounted for just 1.3% of all Minnesota tornadoes since 1950.

Tornadoes during the month of March are an unusual occurrence in Minnesota when compared to the rest of the spring and summer months.[40] Before this outbreak, there had been only six tornadoes ever recorded in the state during March, and since this outbreak there has only been one.[41] This outbreak also marks the first time in Minnesota history that two tornadoes were recorded on the same day in March,[42] as well as the first time since 1921 that there have been multiple tornado fatalities on the same March day.[43] Despite the historical significance of this outbreak, this was not the earliest calendar year tornado to touch down in Minnesota; that record is held by a tornado that touched down near Truman on March 18, 1968.[44]

With a path of 67 miles (108 km), the Comfrey tornado was the fifth longest track tornado on record in Minnesota history.[42] It is however the longest continuous–track tornado in Minnesota history, meaning that it was the longest to have been observed to always be in contact with the ground.[42] The Comfrey F4 tornado is also the strongest tornado ever measured in Minnesota during the month of March. The previous strongest were two F3 tornadoes that occurred on March 27, 1905 and March 26, 1921.[42]

Due to the magnitude of this event along with the time of the year that it took place, the Comfrey – St. Peter tornado outbreak was named the top Minnesota severe weather event of the 1990s by Metro Skywarn, an organization that works with the National Weather Service to coordinate Skywarn storm spotters in Minnesota.[45]

See also

References

  1. ^ a b c d e f g "What Weather Conditions Made This Happen?". The Southern Minnesota Tornadoes of March 29, 1998. NWS - Twin Cities. March 6, 2008. Retrieved 2008-03-13. {{cite web}}: Check date values in: |date= (help)
  2. ^ Wood, Amanda (2006). "Mesoscale Supercell Dynamics of the Comfrey/St. Peter Tornado Outbreak March 29, 1998" (PDF). University of Wisconsin. Retrieved 2008-06-14. {{cite journal}}: Cite journal requires |journal= (help)
  3. ^ a b c d e "The National Weather Service Perspective". The Southern Minnesota Tornadoes of March 29, 1998. NWS - Twin Cities. April 20, 2008. Retrieved 2008-05-08. {{cite web}}: Check date values in: |date= (help)
  4. ^ a b c "What National Weather Service Forecasts and Warnings Were Issued?". The Southern Minnesota Tornadoes of March 29, 1998. NWS - Twin Cities. March 6, 2008. Retrieved 2008-05-08. {{cite web}}: Check date values in: |date= (help)
  5. ^ "Event Record Details - Brandon hail". National Climatic Data Center (NCDC). March 29, 1998. Retrieved 2008-03-10. {{cite web}}: Check date values in: |date= (help)
  6. ^ "Event Record Details - Hardwick hail". NCDC. March 29, 1998. Retrieved 2008-03-29. {{cite web}}: Check date values in: |date= (help)
  7. ^ "Event Record Details - Edgerton hail". NCDC. March 29, 1998. Retrieved 2008-03-29. {{cite web}}: Check date values in: |date= (help)
  8. ^ a b "Storm Events". NCDC. Retrieved 2006-12-22.
  9. ^ a b c d e f "Five Year Anniversary of the Comfrey/ St. Peter Tornado Outbreak". National Oceanic and Atmospheric Administration (NOAA). 2003-03-26. Retrieved 2006-12-22.
  10. ^ "Event Record Details - Avaca tornado". NCDC. March 29, 1998. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  11. ^ a b "Event Record Details - Westbrook tornado". NCDC. March 29, 1998. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  12. ^ a b "What Happened?". The Southern Minnesota Tornadoes of March 29, 1998. NWS - Twin Cities. March 6, 2008. Retrieved 2008-03-13. {{cite web}}: Check date values in: |date= (help)
  13. ^ Steil, Mark (March 30, 1998). "Living Through the Tornado in Comfrey". Minnesota Public Radio. Retrieved 2008-07-20. {{cite news}}: Check date values in: |date= (help)
  14. ^ a b c d e f g "Event Record Details - Comfrey tornado". NCDC. March 29, 1998. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  15. ^ a b Seeley, Mark (2006). Minnesota Weather Almanac. Minnesota Historical Society press. pp. 196–197. ISBN 0–87351–554–4. {{cite book}}: Unknown parameter |middle= ignored (help)
  16. ^ Steil, Mark (March 29, 1999). "Tornado Anniversary". Minnesota Public Radio. {{cite news}}: Check date values in: |date= (help)
  17. ^ "Event Record Details - Courtland tornado". NCDC. March 29, 1998. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  18. ^ "Twisters kill two in southern Minnesota". Associated Press. 2000-03-14. Retrieved 2006-12-22.
  19. ^ a b c Thomas, Matt (February 29, 2008). "Gustavus to Commemorate Tenth Anniversary of 1998 Tornado". Gustavus Media Relations. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  20. ^ Garrison, Luke (March 14, 2008). "Detestation and Renewal". The Gustavian Weekly. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  21. ^ a b c "Event Record Details - Nicollet tornado". NCDC. March 29, 1998. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  22. ^ a b c Stachura, Sea (March 28, 2008). "Ten years after devastating tornadoes, communities thriving". Minnesota Public Radio. Retrieved 2008-05-15. {{cite news}}: Check date values in: |date= (help)
  23. ^ a b c d "Event Record Details - Cleveland tornado". NCDC. March 29, 1998. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  24. ^ a b "Twisters kill two in southern Minnesota". Associated Press. March 14, 2000. Retrieved 2008-05-15. {{cite news}}: Check date values in: |date= (help)
  25. ^ "Event Record Details - Lonsdale tornado". NCDC. March 29, 1998. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  26. ^ "Event Record Details - Hastings tornado". NCDC. March 29, 1998. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  27. ^ "Event Record Details - Wabasha tornado". NCDC. March 29, 1998. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  28. ^ "Event Record Details - Maxville tornado". NCDC. March 29, 1998. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  29. ^ "Event Record Details - Tomahawk tornado". NCDC. March 29, 1998. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  30. ^ "Storm Event Database". National Climatic Data Center. Retrieved 2008-03-24.
  31. ^ "Designated Counties for Minnesota Tornadoes and Severe Thunderstorms". FEMA. April 1, 1998. Retrieved 2008-05-23. {{cite web}}: Check date values in: |date= (help)
  32. ^ "Legislature quick with tornado relief". Associated Press. April 7, 1998. Retrieved 2008-07-24. {{cite news}}: Check date values in: |date= (help)
  33. ^ a b Millett, Larry (March 26, 1999). "Restoration of historic buildings 'remarkable'" (PDF). St. Paul Pioneer Press. Retrieved 2008-06-14. {{cite news}}: Check date values in: |date= (help)
  34. ^ Reabe, Rachel (March 29, 1999). "Mainstreet Radio Special: The Tornado Anniversary". Minnesota Public Radio. Retrieved 2008-05-15. {{cite news}}: Check date values in: |date= (help)
  35. ^ Galbally, Erin (March 29, 2001). "St. Peter Grows Despite Tornado". Minnesota Public Radio. Retrieved 2008-03-14. {{cite news}}: Check date values in: |date= (help)
  36. ^ Steil, Mark (April 13, 1998). "Nearby Schools Welcome Comfrey Students". Minnesota Public Radio. Retrieved 2008-03-14. {{cite news}}: Check date values in: |date= (help)
  37. ^ Steil, Mark (April 3, 1998). "Will Comfrey Save Its Tornado-Damaged School?". Minnesota Public Radio. Retrieved 2008-07-24. {{cite news}}: Check date values in: |date= (help)
  38. ^ Steil, Mark (November 20, 1998). "Construction Drives Comfrey Comeback". Minnesota Public Radio. Retrieved 2008-07-24. {{cite news}}: Check |url= value (help); Check date values in: |date= (help)
  39. ^ "US tornadoes from 1950-2007". Tornado History Project. March 29, 1998. Retrieved 2008-07-24. {{cite web}}: Check date values in: |date= (help)
  40. ^ "Probability (%) of Tornadoes in March" (GIF). National Severe Storms Lab. November 14, 2006. Retrieved 2008-06-14. {{cite web}}: Check date values in: |date= (help); Cite has empty unknown parameter: |coauthors= (help)
  41. ^ "Event Record Details - Adams tornado". NCDC. March 29, 1998. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  42. ^ a b c d "How Historically Unusual Was This?". The Southern Minnesota Tornadoes of March 29, 1998. NWS - Twin Cities. March 6, 2008. Retrieved 2008-05-08. {{cite web}}: Check date values in: |date= (help)
  43. ^ "Minnesota torandoes in March since 1950". Tornado History Project. 1950 - 2006. Retrieved 2008-05-15. {{cite web}}: Check date values in: |date= (help)
  44. ^ Lynch, Mike (2007). Mike Lynch's Minnesota Weather Watch. Voyageur Press. p. 40. ISBN 13: 978–0–7603–2863–7. {{cite book}}: Check |isbn= value: invalid character (help)
  45. ^ Johnson, Dave (2006-06-30). "Top 10 Minnesota Severe Weather Events 1990-1999". Metro Skywarn. Retrieved 2006-12-22.

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=1998_Comfrey–St._Peter_tornado_outbreak&oldid=227568102"