On Thursday July 29th 2010, a NOAA's National Weather Service Survey Team visited the Sibley North Dakota area to assess the damage from the storms that struck the area early on July 27th. Based on this survey the tornado was rated as an EF2 on the Enhanced Fujita Scale. The NWS Storm Damage Survey Team from Grand Forks has confirmed an EF2 tornado in Barnes County from about 2 miles east of Sibley to 11 miles north of Tower City in Cass County. The tornado began at approximately 1230 am CDT on July 27 2010, and continued until Approximately 1 am CDT. The total path length was approximately 18 Miles long. The tornado had a maximum width of four tenths of a mile.
The initial tornado touchdown occurred at a farmstead about 2 miles east of Sibley. Several Quonsets were heavily damaged, and one was totally destroyed. Numerous trees were uprooted, and a grain bin was destroyed and carried for one quarter of a mile. Many other grain bins were also heavily damaged. Wind speeds at this location were estimated around 110 mph, or a low end EF2 tornado.
The most significant damage from this tornado was done to a farmstead about 3 miles south of Pillsbury. A Quonset building was destroyed, and 2 other well constructed large farm equipment storage buildings were heavily damaged with the roof torn off of each building. This debris was deposited about one quarter of a mile away from this farmstead. The damage indicated wind speeds of 120 mph at this farmstead, or EF2 damage.
In addition, the damage indicated that a weaker satellite tornado occurred to the south of the main tornadic circulation about 3 miles into the path of the main tornado. Damage with this satellite tornado indicated a low end EF1 tornado with significant tree damage in some areas due to wind speeds up to 95 mph.
In addition to the tornado damage, widespread straight line wind damage was found in portions of western Barnes county into Cass county. The most significant damage was noted about 13 miles south of Hannaford near the Barnes and Griggs county line. Wind speeds here were estimated near 100 mph and significant tree damage was noted over a widespread area.
Below is an image of the tornado track based on the survey. Click on the thumbnail for a larger image.
Below is an image, showing the approximate path of some of the wind damage surveyed Thursday July 29th. The damage occurred with a second group of severe thunderstorms around 330 to 400 am. Damaging winds were also reported farther east into Cass County, however this is the area which received the most consistent damage.