Amarillo Severe Weather Event - June 21, 2004
By David Hennig

On June 21, the Amarillo metropolitan area experienced perhaps the worst wind and hail event in it's history. Numerous reports of baseball to softball size hail were reported mainly west of interstate 27 in Amarillo. While hail this large isn't that uncommon in the Panhandles region, what is uncommon is the fact that the hail fell over such a large area which was densely populated. In addition, 7 brief tornadoes occurred with this storm though none were within the city limits of Amarillo. Preliminary estimates put damages possibly as high as $100 million to homes, vehicles, businesses, and other property. Below is a meteorological description of how events unfolded during the late afternoon and evening of Monday, June 21.

The Storm Prediction Center had the entire Texas and Oklahoma panhandles outlooked for a slight risk of severe weather due to moderate instability and numerous boundaries across the area. A cold front had become stationary in the northern Texas panhandle, while an outflow boundary from thunderstorms the previous night in Oklahoma was moving westward across the central Texas panhandle. Perhaps most significant of all was a weak area of low pressure developing along the outflow boundary during the day in western Potter county and eastern Oldham county. This low would locally enhance the surface pressure gradient causing winds to increase from the east and southeast across the central panhandles. The low would also cause the front which had become stationary in the northern panhandles, to make one final push to the south and lay along the Canadian River valley. Amazingly it was a feature called horizontal convective rolls, which is common to the tropical Gulf coast region, that would cause the first thunderstorms to begin. Horizontal convective rolls occur when low level shear causes developing cumulus clouds to organize into many linear rows resembling furrows in a field.

One horizontal roll became especially pronounced and intersected the front near the Canadian River and highway 87 about 15 miles north of Amarillo. The first thunderstorm developed in this location and a spotter reported penny size hail at 5:27 pm CDT. A severe thunderstorm warning was issued for Potter county at this same time and even though this first thunderstorm dissipated, rapid development was noted further west. A second severe thunderstorm developed near Valley de Oro where golfball size hail was reported at 5:45 pm. The thunderstorm tried to move toward the northeast however strong convergence along the front and convective rolls caused the storm to continually redevelop and remain in one place. Southeast surface winds enhanced by the low in eastern Oldham county created shear great enough for the storm to begin to tilt and rotate. Spotters from the surrounding area began to converge on the storm and its rotation could even be observed from our office located in east Amarillo near Rick Husband airport.

The initial severe thunderstorm warning was due to expire at 6:30 pm and a tornado warning was then issued due to the strong rotation observed with the storm both visually and by radar. Despite the strong low level rotation, only brief funnel clouds were observed for the next half hour. By 7:00 pm, the developing cold pool from the heavy rain and hail began pushing the front slowly south, further enhancing the rotation within the low levels of the thunderstorm. Finally at 7:15 pm, the first of four brief tornadoes was observed 3 miles west of Bushland. It was also at this time that the rear flank downdraft would alter the storm's motion as it began moving towards the southeast at about 20 mph, directly towards the western half of Amarillo. A tornado warning was reissued for Potter county and another was issued for Randall county at 7:30 pm, however it would not be tornados but rather hail and strong straight line winds that would be doing the damage in Amarillo. Baseball to softball size hail fell across western Amarillo with most damage occuring west of Bell St. Windows and skylights were especially vulnerable to the hail and once broken, allowed one to two inches of rain into the structure adding to the damage. Strong straight line winds caused other damage including overturning several travel trailers and boats. At 7:56 pm NWS doppler radar indicated a very pronounced hook in the reflectivity product over southwest Amarillo, at which time a brief tornado was reported near McCormick road 4 miles west of I-27. It was also at this time that NWS doppler radar indicated storm relative motion winds at 1,000 ft of 140 mph heading into the storm, with about 75 mph storm relative winds heading away from the storm.

The thunderstorm went through an initial occlusion phase where the hook echo briefly dissappeared but it then reappeared at about 8:16 pm as the storm crossed I-27 between Amarillo and Canyon. At 8:17 pm another brief tornado formed at the intersection of FM 1541 and Nance Road and was the only one known to have caused damage. The tornado was only on the ground for 2 minutes but caused minor damage to 3 homes and major damage to a fourth when its entire roof was destroyed. A second thunderstorm moved into Amarillo from the northwest at about 9:45 pm also exhibiting strong rotation and brief hook echos on the radar reflectivity data. A tornado warning was issued for this storm at 9:30 pm and while no tornados were observed with the storm, it did bring strong straight line winds with 68 mph being recorded at Rick Husband airport.

Amarillo was not the only city affected by severe thunderstorms on this day. Many severe thunderstorms developed across the Texas panhandle affecting Stinnett, Canyon, Romero, Sunray, Stratford, Boys Ranch, Channing, Darrouzett, Follett, Pampa, Lefors, Groom, Clarendon, and Palo Duro State Park. I also want to mention that the town of Gruver was hit hard by hail that broke many windows on the evening of Friday, June 18th. While it is easy to be upset over the damage that these storms have caused, let's also be thankful that the damage was not much worse, because looking at the radar imagery from that evening it is still hard for me to believe that a tornado did not move across the city of Amarillo. Thanks to all the spotters who kept an eye on the storms as well as everyone who phoned in their weather reports. Our job is made much easier due to your hard work.