MAY 27-28, 2001 DERECHO
"The People Chaser Derecho"

Figure 1. Area affected by the May 27-28, 2001 derecho event (outlined in blue). Curved purple lines represent the approximate locations of the "gust front" at three hourly intervals. "+" symbols indicate the locations of wind damage or wind gusts (measured or estimated) above severe limits (58 mph or greater). Red dots and paths indicate tornado events.

On Sunday afternoon May 27th, 2001 isolated supercells, some producing brief tornadoes, developed over western Kansas. As the outflow of cold air from the supercell rains increased, a gust front developed over southwestern Kansas and began moving rapidly southeastward. The supercells associated with the gust front eventually evolved into a bow echo squall line although some supercells continued to be embedded within the line of storms. The southeastward moving bow echo storm system produced a derecho event with significant wind damage over a large portion of the southern Plains (Fig. 1).

The maximum storm wind gust in Kansas reached 100 mph near Garden City as measured by the Doppler on Wheels research vehicle. In Oklahoma the maximum measured wind gusts reached 94 mph at Quail Springs Mall in the Oklahoma City metropolitan area and 93 mph at the Ardmore Oklahoma Mesonet station. A maximum wind gust in Texas reached 78 mph in the suburbs of Fort Worth. In many areas the severe storm wind gusts lasted 10 to 20 minutes before subsiding.

The Oklahoma Mesonet network proved to be quite helpful in determining the nature and details of the derecho's severe winds (Fig. 2) . As the derecho crossed Oklahoma, two bands of stronger maximum wind gusts (70 mph and greater) were recorded in the dense network of Oklahoma Mesonet weather stations. These narrow bands of stronger winds (red areas on Fig. 2) within the more general band of severe derecho winds (blue area on Fig. 2) were associated with embedded supercells within the line of thunderstorms and bow echoes.

Figure 2. Official maximum wind gusts in mph measured by the Oklahoma Mesonet Weather Stations as the May 27-28, 2001 derecho crossed the state. Gusts above 50 mph are outlined in blue. Gusts above 70 mph are outlined in red, and gusts about 90 mph are shaded in yellow. Note that the isolated area of winds above 70 mph over northeastern Oklahoma was associated with storms separate from the derecho producing squall line.

Many power poles and lines were blown down as the derecho storm system roared south southeastward across the southern Great Plains. This resulted in many towns and rural areas losing electrical power. In central Oklahoma alone, including the Oklahoma City metropolitan area, 160,000 residents lost electrical power. Many buildings were also damaged with some roofs blown off. Several mobile homes were overturned and at least a half dozen semi-trucks were blown over along Oklahoma highways. The worst damage, estimated at over tens of millions of 2001 dollars, occurred in southern Oklahoma and included the cities of Lawton, Ardmore, Dougherty, and Hugo.

In Oklahoma one person was killed by a falling telephone pole in Lawton and four people were injured near Canton Lake when a mobile home overturned. In northern Texas a women was severely injured when hit by a tree limb at a campground near Lake Texoma.

Animated Regional NWS Radar Imagery shows the evolution of the derecho producing convective system over the southern Great Plains during the afternoon of May 27 and early morning hours of May 28, 2001.

Animated NWS Radar Imagery from Norman, Oklahoma shows the evolution of the May 27-28, 2001 derecho producing convective system as it crosses central Oklahoma.

Animated NOAA Visible Satellite Imagery shows the early evolution of the derecho producing convective system over western Kansas (early afternoon until 7 PM CDT on May 27, 2001).

As it turned out, many storm chasers and several scientific researchers traveled to southwestern Kansas on Sunday, May 27th to observe the development of supercells and tornadoes. The supercells did develop and some tornadoes occurred. However, it wasn't long before the gust fronts produced by the isolated supercells merged and began racing southeastward at speeds ranging from 50 to 55 mph. Some of the storm chasers drove southward or southeastward to keep ahead of developing derecho gust front with the hope of observing new isolated supercell development. However, the derecho became a "people chaser" and overtook many of the storm chasers before they could outrun it!

Some unique features about the May 27-28, 2001 derecho storm system are the large number of photographs and some video clips that were taken by storm chasers and the detailed scientific radar images that were gathered by a tornado research team. Some pictures, a video clip, and radar signatures are shown below and the locations where the data were gathered are shown on Fig. 3.

Figure 3. Area affected during the early stages of the May 27-28, 2001 derecho (outlined in blue). Curved purple lines represent the approximate positions of the derecho "gust front" at 7 PM and 10 PM CDT. The orange letters represent the locations where people experienced this derecho event and provided information (stories, photographs, etc.) for this web page.

Near the beginning of the event, a scientific team with a mobile radar known as the "Doppler on Wheels" was able to observe the initiation of the derecho producing gust front. The team was located in southwestern Kansas just to the south of Garden City (orange "A" of Fig. 3).

Detailed radar imagery from the Doppler on Wheels shows the change in the storm system as it develops into a derecho event. Some of this imagery has been provided by scientific team member Curtis Alexander and can be observed by clicking here.

Because it was relatively dry in this area of the High Plains, the western portion of the gust front was becoming a "haboob" with a deep layer of dust and blowing sand. NWS Storm Prediction Center meteorologist Roger Edwards observed this development just southeast of Sublette, KS (orange "B" on Fig. 3), and as the haboob engulfed him intense blasts of sand scratched and pitted his car's windshield. A wind measuring device that Roger had with him measured a wind gust to 68 mph. After the gust front passed, Roger drove southward at a speed of 60 mph. As he was driving he held his hand out the window and could feel no wind at all against his hand.....an extremely unusual experience!

About 20 miles to the south southwest of Roger's location, Christopher Godfrey observed the approaching derecho gust front on State Highway 51 approximately 10 miles north northwest of Liberal, KS (orange "C" on Fig. 3). Christopher's photographs (Figs. 4 and 5) show the "haboob" characteristics up close with well defined wedges of brown dust and sand rushing southward with the gust front.

Photo by Christopher Godfrey, used with permission

Figure 4. Looking west along State Highway 51 at a point about 10 miles north northwest of Liberal, Kansas (orange "C" on Fig. 3). Two bulging wedges filled with dust and sand, which are a part of the derecho gust front, are racing southward (towards the left).

Photo by Christopher Godfrey, used with permission

Figure 5. Looking east along State Highway 51 at the same point as in Fig. 4. A portion of the gust front filled with dust and sand has crossed the highway moving rapidly to the south (towards the right).

As the storm system gust front moved southeastward into Oklahoma semi-trailer trucks were overturned in several places. One of the first ones blown over was on Oklahoma Highway 3 near the panhandle (see Fig 6). Several others were blown over at points along I-40 west of Oklahoma City as the intense derecho winds blew across that major east-west highway.

Photo by Dave Lewison, used with permission

Figure 6. Semi-trailer truck overturned by derecho winds about 25 miles northwest of Woodward, Oklahoma (orange "D" on Fig. 3) on May 27, 2001.

Paul Knightley, a meteorologist from England, was viewing the derecho event as it was approaching near Shattuck, Oklahoma (orange "E" on Fig. 3). To see Paul's time-lapse video clip of the approaching derecho, click here.

 

(References.....Miller, Andra, Evans, and Johns, 2002; Storm Data for May 2001)

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