National Weather Service United States Department of Commerce

Flash Flood Threats in the Northeast and Southeast; Excessive Heat in the Southwest

Heavy rain will lead to isolated flash flooding threats along coastal New England, and Florida today. Excessive heat will continue to impact the Southwest. Dry, gusty winds, and possible dry lightning will contribute to a critical fire weather threat today across the Interior Northwest. Scattered storms, some severe, are expected Saturday from the northern Plains toward the upper MS Valley. Read More >

Slide 7

16th Street Overpass - Bridge Creek

The first overpass fatality of the event occurred at the 16th Street overpass bridge over Interstate 44 in rural Newcastle (this is just east of Bridge Creek, where F5 damage occurred). The upper two photographs were taken in late September by the author and are different views of the west side of this bridge where the people were seeking shelter. Close examination of the upper left picture reveals several things. First, the construction of this overpass is very different from the one on the Kansas Turnpike as seen in slide 9. There is only a tiny ledge that is not big enough for a person to crawl up underneath. Also, the bridge support girders are skinny. Second, there is a large amount of red clay dirt that has been sprayed up underneath the overpass. On the concrete, one can clearly see the silhouettes of the people where they were crouching. The upper right image is looking northeast along Interstate 44 in the direction of Oklahoma City. A piece of metal debris is clearly seen embedded in the bridge. The lower left photographs were taken in the days just after May 3. It is looking northwest with the damage path the scoured red area. This shows clearly that this bridge took a direct hit from the tornado. This picture also illustrates another point that was already mentioned in slides 4 and 6: the wind direction at any point that is near a tornado's path will experience a rapid and sometimes 180 degree change in the wind direction during tornado passage. This is in stark contrast to a 'straight line' wind event (or downburst), which is the most common damaging wind phenomenon associated with severe thunderstorms. In the case of a downburst wind, the wind generally comes from about the same direction throughout the event. During the May 3rd tornado case, the people were seeking shelter under the west side of the bridge, perhaps assuming that being on the same side of the bridge as the direction from which the tornado was approaching would offer the most protection. This might be true if the winds were only from that direction during the event. During the tornado, unfortunately, as it approached from the southwest, the initial strong wind was from the southeast, directly into the west side of the bridge where they were crouched! If they had taken shelter under the east side of the bridge, they would have been protected somewhat from the tornado's initial winds; however, as the vortex passed, the wind would quickly shift, with the strongest wind from the northwest on the backside of the tornado!

The final two pictures show that a violent tornado can still cause tremendous devastation, even in a relatively rural area where debris in the flow might be expected to be less than in an urban area. The lower right photo in the foreground is the tornado as it appeared near Bridge Creek (located just west of Newcastle) just before 7 PM CDT. The tornado was producing F5 intensity damage at this time. The lower right photo was taken in the damage path just minutes after the tornado passed by NSSL student Jason Lynn. In the center of the photo is what remains of a tree that was completely de-barked and reduced to a splintered 3-foot tall stump, apparently the result of impacts from "natural" debris (e.g., gravel, parts of other trees, etc.). This clearly illustrates that even 'natural' debris can be extremely destructive, especially in a strong or violent tornado; a tornado need not have structural objects or automobiles entrained into its circulation and debris cloud to make it extremely dangerous to unsheltered humans.

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