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Cool and Dry in the East; Turning Stormy in the Northwest

Much cooler temperatures behind a cold front will bring a feeling of fall to the East Coast today. In addition, an active fall storm pattern developing in the Pacific Northwest this week will bring areas of heavy rain and high elevation snow. Northern California will benefit from rainfall this week that will aid firefighters given the recent large wildfires. Read More >

Red Rock Tornado
 
The April 26, 1991 Red Rock Tornado - Photo courtesy of Doug Speheger
View: Facing north along U.S. 77 in Noble County Oklahoma at 7:45 pm CDT, April 26, 1991. The Red Rock tornado is just ¾ of a mile north of the OU School of Meteorology radar research team and is moving from left to right. Tornado photo is provided courtesy of and © 1991 Doug Speheger.
 

Summary

 

The mid to late 1980s were a relatively calm era in Oklahoma and north Texas tornado history, at least as far as the lack of violent tornadoes (tornadoes classified as F4 or F5 on the Fujita Scale). After April 29, 1984 when a violent tornado struck Mannford (near Lake Keystone), there were no violent tornadoes in the state for almost 7 years. This is the longest period of time that the state has gone without a violent tornado since tornado data began to be regularly compiled in 1950, and likely dating back to statehood.

Within the Oklahoma and north Texas counties currently served by the NWS Norman, there were no violent tornadoes for almost 10 years after the Binger tornado of May 22, 1981. Furthermore, no violent tornadoes had occurred within the entire state of Oklahoma since 1984. Unfortunately, those streaks ended on April 26, 1991.

The day started ominously as storms formed across central and western Oklahoma in the early morning hours and moved northeast. A tornado struck the town of Tonkawa in northern Oklahoma about an hour after sunrise. These early storms moved northeast into Kansas and weakened in the late morning hours, but a dry line remained across central Kansas into central Oklahoma.

Storms redeveloped in the afternoon along the dry line and an outbreak of tornadoes across much of the central and southern plains ensued. Before the event was over, 55 tornadoes had touched down in Oklahoma, Texas, Kansas, Missouri, Nebraska and Iowa, including five violent tornadoes that occurred in southern Kansas and Oklahoma. The deadliest tornado occurred in the Wichita, Kansas area when an F5 tornado moved through the southern and eastern portions of the Wichita metropolitan area, including McConnell Air Force Base and the town of Andover.

Four other tornadoes received F4 ratings in this outbreak, with three of these occurring in Oklahoma. One of these overturned several cars on the Cimarron Turnpike before the striking the towns of Westport and Skiatook. This tornado killed one person and injured another 24. A second F4 tornado injured 22 when it struck Oologah, Oklahoma to the northeast of Tulsa.

class="summary"The third violent tornado in Oklahoma was the only one to strike within the NWS Norman area of responsibility, initially touching down east of Enid, about 2.5 miles east of Garber, and it is this tornado that became known as the "Red Rock" tornado. It touched down at 6:30 pm, and moved northeast about 66 miles over the next hour and a half, making this one of the longest tornado paths documented in Oklahoma. At times, the tornado was about 3/4 of a mile wide. Fortunately, despite the long path of this large tornado, there were no fatalities and only six injuries, none of which were serious. This tornado crossed Interstate 35, but did not directly strike any towns. It got its name as it passed between the communities of Marland and Red Rock.

This tornado was also noteworthy because it was well documented by severe storm researchers. A research team from the University of Oklahoma (including current NWS Norman forecaster Doug Speheger) was able to record wind information from the tornado using a portable Doppler Radar. The radar was set up along U.S. Highway 77 just a mile or two north of State Highway 15 in Noble County, and the tornado crossed U.S. 77 north of the research crew.

As the tornado passed the highway, peak wind speeds over 270 mph were recorded with the Red Rock tornado, which was the highest known measured wind speed of a tornado until May 3, 1999 tornado near Bridge Creek, Oklahoma. It should be noted however that very few tornadoes have actually had wind speeds measured at close range by Doppler Radar. The Red Rock tornado was likely only the 10th tornado to ever have had radar-based wind speed measurement taken.

In the vast majority of tornadoes, the intensity is estimated based upon the damage that is caused, so it is difficult to compare the intensity of the Red Rock tornado to other historic tornadoes. The wind speeds measured were technically within the wind speed range given by Fujita as F5 (winds above 260 mph), but the wind speeds were measured at a height closer to the top of the visible tornado, rather than to the part of the tornado near the ground. Therefore, it is unclear how strong the winds may have been closer to the ground. An F4 rating was assigned based on the destruction of a few houses in Noble County observed during the post-storm damage survey.

 

Other Photos of the April 26, 1991 Red Rock Tornado

 

The following photos of the April 26, 1991 Red Rock tornado are provided courtesy of storm chaser Gene Moore and are from the NWS Tulsa, OK April 26, 1991 event web page.

Photo of the April 26, 1991 Red Rock Tornado is courtesy of Gene Moore
Photo of the April 26, 1991 Red Rock Tornado is courtesy of Gene Moore
Photo of the April 26, 1991 Red Rock Tornado is courtesy of Gene Moore
Photo of the April 26, 1991 Red Rock Tornado is courtesy of Gene Moore