National Weather Service Forecast Office

April 9-10 Severe Weather Outbreak

Widespread wind damage resulted from an intense line of thunderstorms that developed into a bow echo as it approached the Metroplex during the early morning hours of April 10. The term bow echo describes the radar presentation of the storms...which accelerates or bows out as a result of the strong winds. While most of the damage surveyed suggested straight-line winds of 70 to 75 mph...at least three tornadoes occurred with the squall line. Two tornadoes occurred with an intense circulation across northeast Johnson County and southern Dallas County. A third tornado was confirmed in Collin County.

Johnson County

The Johnson county tornado touched down north of Alvarado near Happy Hill at approximately 330 am cdt and traveled northeast for approximately 3 miles to Pleasant Point. Several homes sustained significant roof damage...and at least three homes were considered total losses. Many sheds...detached garages...and other small outbuildings were damaged or destroyed. Several trees were uprooted...and at least two fell onto homes. Power lines were downed throughout the area. This tornado is rated ef-1 with estimated wind speeds of 90 to 95 mph. The path width is estimated to be approximately 50 yards wide.

Dallas County

The second tornado touched down in Desoto at approximately 4 am in the central portion of the city along Meadowbrook road just west of Hampton road and traveled east-northeast to near the eastern limits of the city just north of wintergreen road. Again...several homes had substantial roof damage...with one home near the beginning of the track losing the majority of the roof. Many downed trees were observed along with damage to sheds and outbuildings. Power poles and power lines were also downed. This tornado is also rated EF-1 with estimated wind speeds of 95 mph and a path width of 40 yards. more isolated damage was reported southwest of the tornado across southwest sections of Desoto...but this damage was more scattered in nature and appears to be the result of straight-line winds.

Collin County

A third EF-1 tornado occurred in Collin County...affecting southwest sections of Allen northeast into southern sections of McKinney. Winds were estimated at 90 to 95 mph. The tornado touched down near the intersection of North Custer Road and Hedgcoxe Road in Allen...and lifted near the intersection of Highway 75 and Highway 121 in McKinney. The average width of the tornado was approximately two tenths of a mile. In Allen...structural damage occurred to approximately 50 homes...with several suffering loss of portions of the roof. A total of 300 residences reported some type of damage on the property...including downed trees and fences. In McKinney...numerous homes suffered roof damage due to loss of part of the roof or impact from debris from other structures. In both cities...many power poles and power lines were downed. Insured losses in Allen are estimated to approach $5 million. Damage estimates from McKinney were not immediately available. Damage at Collin County Regional Airport in McKinney appears to be the result of downburst winds.

A supercell thunderstorm developed in West Texas during the afternoon of April 9. From Stephens County to the Red River...the storm left a 150-mile path of severe weather. Two tornadoes were confirmed in Stephens County...and a second occurred in Palo Pinto County.

Stephens County

Based on ground and aerial surveys of the damage area...it appears two tornadoes occurred in Stephens County. The first tornado developed along Farm Road 576 east of the Eolian community. Trees and a shed were damaged west of the intersection of F.M. 576 and F.M. 3418. A large metal building was damaged along F.M. 3418 and several large storage containers were blown across the road. This tornado will be rated as an EF-0 with winds of around 80-85 mph. Path length was 2.3 miles and average path width around 75 yards.

The second damage swath started approximately 1/2 mile west of U.S. 183 and south of F.M. 2231. Power pole damage was noted along F.M. 2231 and U.S. 183. Roof and barn damage occurred along U.S. 183 as well.

The most significant damage occurred at and just west of the Stephens county airport. Several homes had considerable damage along county road 150. Several of the airport buildings had overhead doors blown in...roof damage...and damage to some of the girders.

Northeast of the airport...additional damage to power poles was noted near the eastern end of F.M. 2231. The damage swath continued across U.S. 180 between Highways 67 and 207. Damage to mobile homes...roofs...power poles...and storage buildings occurred in this area. This tornado will be rated as an upper-end EF-1 with winds near 110 mph. Path length was 7.1 miles...and the average path width was around 400 yards.

Palo Pinto County

Based on a survey of the damage near the Oran community in northeast Palo Pinto county...it was determined that a tornado affected this area. The damage swath began just west of Oran. Several trees were uprooted or had large limbs snapped. A few homes in Oran had portions of roofs removed. East of Oran on F.M. 52...power poles were snapped. This tornado will be rated an EF-1 with winds of 85-90 mph. Path length was 1.6 miles and average path width was 100 yards.

Radar Images from the April 9-10 Severe Weather Outbreak

This radar imagery was taken from the WSR-88D at KDYX on Wednesday, April 9, 2008. The time on the radar imagery is 2220Z (520 PM CDT) and is zoomed into the storm that is near the center of Stephens County TX.

Large picture of radar reflectivity over Breckenridge.

Small picture of radar winds over Breckenridge.

The reflectivity image shows the classic hook echo associated with the intense supercell thunderstorm. The brightest red colors indicate very heavy rain and hail that were occurring with the storm. Although the city of Breckenridge is just south of the heaviest rain and hail at 520 PM, the area near the town is bounded by the hook echo, which is formed when a well-developed circulation wraps rain in a counter-clockwise direction.

The Doppler velocity image was also taken from the KDYX 88D, which is 25 miles to the southwest of Breckenridge. The Storm Relative Mean Radial Velocity image clearly shows a well-defined circulation just south of Breckenridge, with the characterstic side-by-side velocity couplet indicating an extremely strong cyclonic rotation.

Metroplex Radar Storm Relative Motion Image

The reflectivity image from the Fort Worth area WSR-88D (KFWS) shows part of the intense squall line as it moved through Tarrant and Johnson Counties toward Dallas County. The time of the imagery is 332 AM CDT. The sharp leading edge of the rain echo, extending from Trophy Club at the top of the image to near Arlington to east of Alvarado, represents the sudden onset of very strong winds associated with the squall line.

The Doppler velocity image, also with a time of 332 AM CDT, shows several interesting features. The strongest outbound doppler base velocities, representing a 75 to 80 mph velocity measurement, were located midway between North Richland Hills and Irving. This pocket of stronger winds progressed northeast across northwest Dallas County into the Carrollton and Plano areas. The second interesting feature is the stronger outbound velocities and weak circulation feature north of Alvarado in Johnson County. This circulation was associated with an area of stronger straight line winds near the circulation. Storm surveys will eventually determine whether or not a brief tornado occurred with the radar circulation feature.