2011 Joplin tornado
The tornado initially touched down just east of the Missouri-Kansas state line near the end of 32nd Street at 5:34 pm CDT (22:34 UTC) and tracked due east, downing a few trees at EF0 intensity. Eyewitnesses and storm chasers reported multiple vortices rotating around the parent circulation in that area. Civil defense sirens sounded in Joplin 20 minutes before the tornado struck in response to a tornado warning issued by the National Weather Service, but many Joplin residents didn't heed them. The tornado strengthened to EF1 intensity as it continued through rural areas towards Joplin, snapping trees and power poles and damaging outbuildings. Widening, the tornado then tracked into the more densely populated southwest corner of the city near the Twin Hills Country Club. It heavily damaged several homes at a subdivision in this area at EF1 to EF2 strength. The tornado continued to strengthen as it ripped through another subdivision just east of Iron Gates Rd. Numerous homes were destroyed at EF2 to EF3 strength at that location, and multiple vehicles were tossed around, some of which were thrown on or rolled into homes.
The now massive wedge tornado then crossed S. Schifferdecker Ave., producing its first area of EF4 damage as several small but well-built commercial buildings were flattened. Consistent EF4 to EF5 damage was noted east of S Schifferdecker Ave and continued through most of southern Joplin. Numerous homes, businesses, and medical buildings were flattened in this area, with concrete walls collapsed and crushed into the foundations. A large steel-reinforced step and floor structure leading to a completely destroyed medical building was "deflected upward several inches and cracked". Steel trusses from some of the buildings were "rolled up like paper", and deformation/twisting of the main support beams was noted. Multiple vehicles were thrown and mangled or wrapped around trees nearby. Several 300-pound concrete parking stops anchored with rebar were torn from a parking lot in this area and were thrown up to 60 yards away. Iowa State University wind engineer Parka Sarkar was able to calculate the force needed to remove the parking stops and found that winds exceeding 200 mph were needed to tear them from the parking lot.
Tornado outbreak of June 13, 1998
In the afternoon and evening of June 13, four supercells which had formed near the dryline over Western Oklahoma entered the central part of the state, two of which produced tornadoes, and two of which only produced strong winds and hail. The first of the two tornado-producing storms produced two tornadoes; the former, which touched down near Longdale, injured a child and caused tree damage, ultimately causing F0 damage. The latter tornado, which was ultimately rated F1, caused roof, window, siding, and porch damage to three houses. It also took off the roof of a barn, destroyed an outbuilding, caused fence damage, and took off the hood of a pickup truck.
The second tornadic supercell produced seven tornadoes. The first two tornadoes touched down near El Reno and caused no damage, earning ratings of F0. The third tornado touched down near Yukon but, as with the other two, caused no damage and was rated F0. A fourth tornado touched down over Lake Hefner in Oklahoma City, eventually causing damage to boats in a dry dock at the Oklahoma City Boat Club. Damage to club facilities and nearby boats was estimated at $250,000. The tornado went on to destroy a storage shed and cause minor roof damage to homes east of Lake Hefner Parkway before it dissipated, having caused only F1 damage. The fifth tornado (rated F1) materialized near NW 84th Street and Walker, going on to displace much of a house's roof decking and uproot street signs. The tornado also damaged vehicles and caused roof damage to houses on 84th, 85th, 86th, 87th, and 88th Streets. The tornado destroyed the western half of a church in this area after it knocked down its walls on three sides and threw part of its roof at a house which resultantly suffered major damage. The sixth tornado, which was anticyclonic, affected the Northwest Oklahoma City/Nichols Hills area. It caused "considerable" damage to a strip mall, unroofed numerous houses, shattered windows, and damaged signs and powerlines. One building saw an exterior wall collapse. An RV was thrown into a house, a car flipped, trees were knocked down, and pieces of shingles and roof decking were blown away. The tornado's ultimate rating of F2 was based on damage limited to a small area, and most damage was actually consistent with that of an F1 tornado.
The seventh tornado produced by the second tornadic storm (rated F2), which affected Northeast Oklahoma City in the Frontier City area, was also the most destructive. The tornado touched down near the Hefner Road/Bryant Avenue intersection before going on to cause major structural damage to numerous businesses. At Frontier City, the tornado damaged vehicles in the parking lot and caused the exterior of a concrete-block building to partly collapse while simultaneously taking its roof off. Inflow into the tornado caused additional damage to nearby areas, and seventeen injuries occurred at the park. East of Interstate 35, a Texaco suffered significant damage, and the tornado lifted and rolled empty semi-truck trailers in the parking lot. A nearby portable building was completely blown away. In the Nottingham and Quail Ridge Run subdivisions, extensive damage was caused to homes' windows, roofs, and garage doors. Some of these homes suffered a significant degree of roof failure despite having still-standing exterior walls. Anchoring between the roofs of these homes and their walls was missing, and it is possible that the intensity of the tornado was near the F3 range in these areas. The tornado caused $1 million worth of damage in North Oklahoma City throughout its track.