"Fort Worth Tornado"
28 March 2000

On the evening of 28 March 2000, two tornadoes struck Fort Worth, Arlington and Grand Prairie, Texas. The Fort Worth tornado touched down west of the city, and moved right through the downtown area. The path length was approximately 3 miles with a path width of 1/4 mile. The tornado was rated as F2 on the Fujita scale at its strongest point. The Arlington tornado began as an F3, and varied from F2 to F0 throughout its 6 1/2 mile path. All the necessary ingredients came together to produce the storms which spawned these tornadoes.

In the upper levels, a deep cutoff low had settled over the Great Lakes, putting the eastern half of the U.S. under a trough, with a weak ridge in the west. A Pacific trough was pushing onshore at 0100Z 28 March; notice the weak wind over the Fort Worth area at this time. The Pacific trough moved quickly inland, flattening out the ridge and becoming negatively tilted. The trough axis was now over the Texas Panhandle as winds at 500mb had increased to near 50 knots by 0000Z 29 March.

The result of the trough was a series of surges of cooler air pushing south and eastward through the Plains. Fronts came through north Texas around 0000Z 26 March, 1200Z 27 March and another dropped down and became stationary along the Texas/Oklahoma border early on the 28th. A surface low deepening in the panhandle in the morning of the 28th helped flow to return from the southeast, drawing warm moist air from the Gulf of Mexico north into central Texas. RUC analyses of surface dewpoint and winds show the moisture axis in east central Texas at 1800Z. By 2100Z, a bulge had formed in the dryline, and the 2200Z surface observations with 50, 55, and 60 degree isodrosotherms illustrate this also. This push of the dryline may have initiated the convection that became the storms around Fort Worth.

The Eta model had a good handle on the area of concern with its 24-hour forecast from 0000Z 28 March. The CAPE bullseye is right over the affected area, while Lifted Index values bullseye the same region. A 0000Z 29 March skew-T shows the Eta was very accurate with its forecast values, with a CAPE of 1112 J/Kg, and Lifted Index of -8.4. Other values were good for severe weather potential, as Totals was 60 and the Bulk-Richardson number was 10.8.

The damages from these tornadoes was estimated at $450 million in the Fort Worth area. 5 deaths were attributed to these storms, with 2 directly from the tornadoes, 2 from heavy flooding in the Arlington area, and one due to baseball sized hail which struck the victim in the head. Hail is a dangerous but infrequent killer. Other historical U.S. hail fatalities included one death in the 1700's, two deaths in the 1800's, and three deaths in the 1900's. The last recorded U.S. hail fatality was on July 30th, 1979 at Fort Collins, Colorado.

Case Study 28