IntroductionOn 29 May, 2004, a system of severe thunderstorms in

northeast Colorado produced an outflow boundary of cold air.

This outflow and resulting temperature gradient contributed to

winds with gusts as high as 40 m/s (90 mi/h). The storm

tracked towards the east-southeast, over land that had been

experiencing an extended drought. The wind, in conjunction

with the land condition, initiated a wind erosion event that

carried soil dust for at least 355 km (220 miles) past Hays,

Kansas. The dust storm caused severe damage to the land

and dramatically lowered visibility. Many traffic accidents and

even two deaths were attributed to the storm. This study helps

to better understand the genesis and progression of such

storms and to evaluate the ability of the USDA-ARS Wind

Erosion Prediction System (WEPS) model to simulate such

events.

J. Tatarko, USDA-ARS; M. Knapp, Kansas State University;S. van Donk, and E.L. Skidmore, USDA-ARS; Manhattan, Kansas

Deadly Dust: A case study of a Great Plain dust storm

USDA-ARS-WERU1515 College Ave.Manhattan, KS 66502

For more information about WEPS, please contact :

Email: weps@weru.ksu.edu; Phone: 758-537-5559

WEPS SimulationsWeather and field data provide a unique opportunity to assess the ability of the

WEPS model to simulate such wind erosion events. For the period 1999-2004,

we obtained detailed historical weather records, soil data for the dominant soils,

average yields, and typical crop rotations for Goodland, Kansas. These data

were used in WEPS and simulations made for 6 year rotations and the event

(5/29/04) using measured and simulated weather (see table below).

Storm observations indicate that while the soil eroded on many fields, on others

it did not (see aerial photos). Interviews with the Goodland DC indicate that crop

rotations on fields that eroded included grain sorghum, corn, and some winter

wheat where the previous drought afforded little residue and poor crop stands in

the spring of 2004. While WEPS did show soil loss likely for the rotations using

simulated weather, losses were much greater using the much drier measured

weather on irrigated crops and still higher for dryland situations. Corners of

some irrigated fields blew (see aerial photos, left) and are considered as dryland

scenarios in the simulations. The Goodland DC indicated that some wheat land

was blowing on 29 May, but WEPS does not show loss for that day for wheat.

However, others interviewed indicated that most wheat land did not erode on 29

May because of sufficient cover but that such land did have erosion events in

April because of poor cover. WEPS did predict erosion on 16&17 April of 2.6 and

7.7 kg/m2 respectively. Dryland grain sorghum and corn did show significant soil

loss for 29 May as was observed in the field by the DC.

11:45 MDT – SE of Akron, ColoradoA severe thunderstorm system, southeast of Akron, Colorado,

causes a downburst. A downburst is the result of hail or large

raindrops falling through dry air. The hailstones melt or

raindrops evaporate – the evaporation demands a lot of energy

so the air is cooled. The higher density cold air falls as a "cold

air balloon". As the cold air balloon falls, a strong downdraft

induces an outburst of damaging winds on or near the ground.

~15:45 MDT – Bird City, Kansas“My anemometer is located only 9 feet off the ground and between

windbreaks and registered in the 50-60 mph range but neighbors

clocked 80-90 mph straight lined winds. It was an unbelievable

storm. It reminded me of some hurricane videos I've seen. The

roar grew until our house shook. The south side of the barn was

blown off its foundation.” - John Coumerih, Bird City, Kansas

15:30 MDT – Goodland, KansasThe National Weather Service (NWS) in Goodland, Kansas

reported 90 mph winds at St. Francis, Kansas and gusts 65–85

mph at Goodland. Prior to this event, the area experienced a six

year drought (see table below) and the topsoil moisture in NW

Kansas was very low by the end of May.  Afternoon temperatures

frequently topped 80 degrees during the month, and only two days

of significant rainfall were reported for the year, prior to May 29th.

17:15 MDT – Grinnell, KansasThe poor visibility caused the Kansas Highway Patrol to close I-70 West of Wakeeney

for about two hours. However, because of the fast moving nature of the storm, at

least 10 vehicle accidents occurred with two resulting in the deaths of two individuals

including Kansas State Senator Stan Clark. NWS reports winds of 69 MPH.

16:00 MDT – Colby, KansasRobert Grace took a series of photos flying near Colby, Kansas. NWS reports winds of

67 mph and “metal roofs ripped from buildings and several power poles were broken”.

Sherman Co. (Goodland) precipitation and departure from normal

Year: 2000 2001 2002 2003 2004 Normal

millimeters: 427 466 280 373 566 504

departure: -77 -38 -224 -131 62

Weather Total Suspension Total Suspension

Continuous Winter Wheat Dryland Simulated 0.1 (0.3) 0.05 (0.2) 0.0 0.0Continuous Winter Wheat Irrigated Measured 0.2 (1.0) 0.1 (0.7) 0.0 0.0Continuous Winter Wheat Dryland Measured 29.0 (129.1) 22.7 (101.3) 0.0 0.0Winter Wheat - Fallow Dryland Simulated 4.3 (19.2) 3.0 (13.2) 0.0 0.0Winter Wheat - Fallow Dryland Measured 38.1 (169.8) 29.1 (129.9) 0.0 0.0Continuous Grain Sorghum Dryland Simulated 9.3 (41.2) 6.3 (28.0) 0.0 0.0Continuous Grain Sorghum Irrigated Measured 0.9 (3.9) 0.5 (2.4) 0.0 0.0Continuous Grain Sorghum Dryland Measured 15.0 (67.0) 10.2 (45.6) 5.7 (25.5) 3.1 (14.0)Continuous Corn Dryland Simulated 3.3 (14.6) 2.0 (8.9) 0.0 0.0Continuous Corn Irrigated Measured 0.1 (0.4) 0.1 (0.3) 0.0 0.0Continuous Corn Dryland Measured 20.9 (92.9) 15.3 (68.2) 7.1 (31.5) 3.7 (16.4)

Rotation

kg/m2 (Tons/Acre)

The study of this storm will help in our understanding of such events including

management systems that control soil loss by wind under these conditions. This

study also provides experience using WEPS with measured weather - essential

to developing a WEPS based dust event warning system for highway,

agricultural, and environmental agencies.