During the period of July 8–9, 1927, a potent upper-air system moved throughout the Interior Plains region, triggering the formation of several tornadoes and causing severe wind events. This tornado outbreak, featuring at least 17 confirmed tornadoes, mainly affected the Canadian province of Alberta; however, effects were also seen in Ontario, Saskatchewan, and the U.S. states of Iowa and Minnesota. Various historic photographs, many of which were important to meteorological studies at the time, originated from this event; this includes Lucille Handberg's photo sequence of a slender, 'sheathed' tornado near Jasper, Minnesota on July 8, and Charlie Jones' photograph of a tornado passing near Vulcan, Alberta on July 8, which has since been digitized and uploaded to the NOAA Photo Archives. An unknown number of injuries was reported, and 3 deaths were confirmed, all being from a tornado that impacted Gull Lake and Wetaskiwin, Alberta, on July 8.

Meteorological background

July 8

The synoptic pattern for July 8, 1927 featured various high-pressure and low-pressure systems interacting throughout the Plains region, generating ample shear and boundary dynamics to cause the formation of tornadoes. Two surface highs overspread Alberta and Wisconsin, and a very strong and well-defined area of low pressure existed over Southern Manitoba, which caused a northward turn in the isotherms in the southeast quadrant of the low. Such a turn is usually associated with an environment supportive of tornadoes, as tornadoes form between the leading warm front and trailing cold front in a low-pressure area. Because the surface low over Manitoba moved slowly, this allowed it to advect very high moisture values into the region. Multiple weather stations, including those at St. Paul, Minnesota, Des Moines, Iowa, Sioux City, Iowa, and Yankton, South Dakota, observed dew point values in the upper-50's and low-60's during the morning of July 8, 1927. By afternoon, the weather station at Yankton even reported a dew point of , which is considered extremely high. In the area, daytime temperatures also reached .

July 9

According to hand-drawn synoptic weather maps on July 9, 1927, an occluded front was draped over northern Alberta, with multiple influencing systems surrounding the occluded front, such as a low-pressure system over Wisconsin, a high-pressure system over the northern Pacific Ocean, and a pair of low-and-high-pressure systems off the southern coast of Alaska. A deep trough extended over Alberta and Montana, creating a highly-sheared environment based on the shear vectors in the area. Much of the tornado-related activity on this day was in the Calgary area, in southern Alberta.

Confirmed tornadoes

July 8 event + List of confirmed tornadoes – Friday, July 8, 1927F#LocationMunicipality / CountyProvince / StateApproximate time (UTC)FatalitiesInjuries FUMaskwacis areaPonokaAlberta18:00–?00Unclassified tornado near Maskwacis, Alberta (previously known as Hobbema), at around 12:00 p.m. MDT. FUHomeglen areaPonokaAlberta18:00–?00Unclassified tornado near Homeglen, Alberta, at around 12:00 p.m. MDT. FURocky Mountain HouseClearwaterAlberta20:30–?0A devastating tornado struck the center of Rocky Mountain House, Alberta, in the afternoon hours of July 8, 1927. Virtually every building in town suffered some form of damage, whether cosmetic or internal. One resident described this tornado as "three minutes of hell unadorned". Despite a direct impact on a populated area, there were no reported injuries or deaths. It is thought that the storm system that produced this tornado also dropped a tornado near Gull Lake and Wetaskiwin, Alberta, which killed three. FUEckville areaLacombeAlberta23:00–?00Unclassified tornado near Eckville, Alberta, at around 5:00 p.m. MDT. F1N of Sherman to NW of JasperMinnehaha (SD), Pipestone (MN)South Dakota, Minnesota00:00–00:4500See section on this tornado — A winding tornado moved from Sherman, South Dakota, to Jasper, Minnesota, in a duration of around 45 minutes. Sherman resident Lucille Handberg's photographs of this tornado are considered some of the finest of their era. FUAspen Beach Provincial ParkLacombeAlberta01:00–?00Unclassified tornado near Aspen Beach Provincial Park, Alberta, at around 7:00 p.m. MDT. FUVulcanWillow Creek, VulcanAlberta01:40–?00See section on this tornado — Various buildings in Vulcan, including the town's curling rink, were severely damaged or destroyed. FUFerrybank to UsonaPonokaAlberta03:00–?00Unclassified tornado near Ferrybank, Alberta, at around 9:00 p.m. MDT. FUGull Lake to WetaskiwinLacombe, PonokaAlberta05:59–?30Various boats in Gull Lake were capsized or lofted considerable distances, up to . Near Wetaskiwin, 3 fatalities occurred when this tornado demolished a granary, where three men were sleeping. The granary was completely swept from its foundation and its debris was bounced "in jumps" for . FURock Valley areaSiouxIowa00Unclassified tornado near Rock Valley, Iowa, on July 8. This tornado is indirectly mentioned in a Weatherwise report on the Jasper tornado. "Minor damage" was caused.

July 9 event + List of confirmed tornadoes – Saturday, July 9, 1927F#LocationMunicipality / CountyProvince / StateApproximate time (UTC)FatalitiesInjuries FUDe Winton areaFoothillsAlberta18:00–?01Near De Winton, several barns and farmsteads were completely destroyed, and a line of poles was downed for . A boy was reported as being severely injured. Hail as large as hens' eggs accompanied the tornado, as did a black sky and "clouds of dust", according to the Calgary Herald. FUIndus areaRocky ViewAlberta18:00–?00Unclassified tornado near Indus, Alberta, at around 12:00 p.m. MDT. FUOkotoks areaFoothillsAlberta18:00–?00Unclassified tornado near Okotoks, Alberta, at around 12:00 p.m. MDT. FUYoungstown areaSpecial Area No. 3Alberta18:00–?00Unclassified tornado near Youngstown, Alberta, at around 12:00 p.m. MDT. FUSW of OkotoksFoothillsAlberta20:30–?00Unclassified tornado southwest of Okotoks, Alberta, at around 2:30 p.m. MDT. FURowley areaStarlandAlberta21:00–?00Unclassified tornado near Rowley, Alberta, at around 3:00 p.m. MDT. FUCereal areaSpecial Area No. 3Alberta22:00–?00Unclassified tornado near Cereal, Alberta, at around 4:00 p.m. MDT.

Jasper, Minnesota

Tornado summary Touching down at around 7:00 p.m. local time and extending from what witnesses described as a boiling mass of clouds, the Jasper tornado took an erratic path to the east, striking multiple farmsteads and properties along its path. At points, the tornado was suspected to have stalled or quickly changed directions, due in part to the disconnect between the tornado's storm base and its surface-level circulation. The tornado initially touched down near Sherman, South Dakota, appearing as a "lead-colored tentacle". It then approached and struck the farmstead of Oscar Kulsrod, removing the chimney from the home, downing several trees, and sucking plate ware from within the home and distributing it across the property. Over two miles, the tornado began to meander to the south, striking the Petersen property, where only one-half of the home was left after the tornado side-swiped it. A windmill, a water tank, and several outbuildings were windrowed over a square mile of farm fields. Reports indicate that acres of corn were uprooted by the tornado and scattered around the prairie.

As the tornado continued to elongate and the disconnect between its surface winds and storm base became even greater, it acquired multiple loops in its condensation funnel. The tornado dissipated near Jasper, Minnesota, first beginning with the visible funnel "snapping in two", followed by it receding back into the storm base. Montgomery Meigs, a retired civil engineer, estimated the base of the tornado to be wide at its widest, and theorized that the damage from the tornado was caused by the intense pressure drop in its core — which, though a common theory at the time, has been disproven since.

In his Significant Tornadoes: 1880–1989 book, Thomas P. Grazulis made an indirect reference to the tornado being F1 in intensity, based on damage to "roofs, windmills, and outbuildings" at the Petersen property. This has been accounted for in the 'confirmed tornadoes' table. Grazulis states that the duration of the tornado was around 45 minutes long.

Lucille Handberg's photographs Lucille H. Handberg, a 16-year-old resident of Sherman, South Dakota at the time of the tornado, observed the Jasper tornado as it moved to the east. Grabbing her camera, she followed the tornado for a quarter of a mile, taking three photographs in the process; Lucille snapped the first photograph as the tornado was approaching the Petersen farm, followed by a second photograph when the tornado was approximately away from her, and a third when the "broom" (base) of the tornado was directly opposite her, with the storm base of the tornado moving at a right angle to its surface connection. These photographs showed the unusual internal dynamics of the tornado, including its 'sheathed' appearance and winding, rope-like structure. Lucille recounted that the tornado continually expanded and contracted throughout its life, as if it were breathing.

These photographs, which in many articles and reports were deemed some of the finest of the era, were widely circulated around global newspaper headlines. It is reported that Lucille Handberg sent her photographs to Washington, D.C. to purchase a copyright holding. Two of the three photos that Lucille had taken appeared in the August 18, 1928 issue of the The Illustrated London News, as well as in other American publications, such as the September 9, 1928 issue of the San Francisco Examiner. This second photo of the sequence was also featured in the 50th anniversary issue of the Life magazine as a two-page spread, though the photo was misattributed to a tornado in 1943.

Vulcan, Alberta

Preceding the cyclone Large hailstones, which witnesses estimated were the size of eggs, or even baseballs in some cases, accompanied the storm that produced the Vulcan tornado. Large crowds were gathered in Vulcan for a Canada Day sports event, which had been postponed the week before due to rain. According to witnesses, the morning of July 8 was warm and clear, but it quickly became humid and "muggy" as storms began to approach in the late afternoon. The hailstones that accompanied the Vulcan supercell smashed through car tops and multiple windows in the downtown area, but nobody was seriously injured, as the people gathered in Vulcan had ample time to seek shelter.

Tornado summary As the damaging hailstones persisted, the Vulcan cyclone spawned "just after 7 p.m.", according to the Lethbridge Historical Society. Beginning near the "Old Mallory section", southwest of Vulcan, the tornado struck a series of farmsteads. At W.J. Montgomery's dairy farm, a barn was reduced to splinters and a heavy iron pump was pulled up out of its well. The Hamilton Johnston farm suffered similar destruction, as a farm equipment barn was destroyed and a large threshing machine was lofted and thrown . In total, 150 acres of pure-bread wheat and summer fallow were completely cleared out by the tornado, as well as multiple oat, corn, and potato fields.