The July 4th holiday weekend brought rounds of heavy rain that resulted in areas of flooding and flash flooding across portions of the South Plains and Rolling Plains. Over a four day period, from July 1st through the 4th, many locations from the southwest South Plains through the southeast Texas Panhandle and the entire Rolling Plains received over 3 inches of rain, with a swath of 5 to 10 inches plus from Terry County eastward through Lubbock, Lynn, Dickens, Garza and Kent Counties. The West Texas Mesonet site located 1 mile north of O’Donnell recorded a 4-day total of 10.24 inches of rain, much of which fell late on the 3rd (Saturday) and early on the 4th (Sunday). The Lubbock Airport officially recorded a 4-day total rainfall of 6.12 inches, and set daily rainfall records on the 2nd and the 3rd, when 2.19 inches and 3.27 inches were recorded, respectively. Interestingly, 6.12 inches of rain already ranks as the 5th wettest July on record. The wettest July occurred in 1976 when 7.20 inches fell.
The rounds of widespread heavy rainfall were a product of deep tropical moisture interacting with several slowly moving upper level disturbances that tracked overhead. The stage for heavy rainfall was initially set, in part by Hurricane Alex. Alex came ashore late on 30th of June, about 100 miles south of Brownsville, Texas, as a strong category 2 tropical cyclone. Alex weakened and eventually lost its identity as it tracked westward into the higher terrain of Mexico, but plentiful amounts of tropical moisture were brought northward into West Texas by southerly winds through much of the depth of the atmosphere. Once the moisture was in place, all that was needed was a trigger, which was supplied by several subtle, but efficient, upper level disturbances.
The first round of rain developed and moved northward into the Rolling Plains and southeastern South Plains late Thursday and early Friday, the 1st and 2nd of July, with scattered half inch to inch plus rain totals. Another couple of rounds of moderate to heavy rainfall followed the next 24 hours, falling across the same area. Rain totals of 2 to 5 inches were common through this period. The repeated rain began to cause flooding problems, mostly around playa lakes and other low lying and poor drainage areas across the central and southern South Plains. Then, to top it off, a more intense area of tropical rain developed during the evening of the 3rd and tracked slowly eastward, bringing copious amounts of precipitation across this same region. Some locations saw another 5 to 10 inches plus with this final round of torrential rain, which resulted in many areas of flooding and flash flooding, especially across parts of Lynn, Lubbock and Garza Counties.
Numerous roads were inundated with water and many roads were closed. Swelling playa lakes flooded many cars, roads and homes, and several high water rescues occurred. Portions of Lubbock, Post and Ransom Canyon were particularly hard hit. A stretch of Farm-to-Market Road 669 was washed out by flowing flood waters south of Post, and large stretches of Highway 380 on the Caprock west of Post were covered in water. Below are a few scenes of the flooding around south Lubbock.
- Though the South Plains region received a large amount of rain during this prolonged precipitation event, even heavier amounts of rain fell into parts of northeast Mexico, as the graphic below demonstrates. The tremendous amount of runoff from all this rain was resulting in major flooding along the Rio Grande from Del Rio southward.
- Another way to put the rain into perspective is to look at the percent compared to normal. The below map shows that most of Oklahoma and Texas saw well above normal during the two week span from late June through early July 2010. Much of the South Plains and Rolling Plains received an astounding 400 to 800% or more of normal. The exception was across the southwest Texas Panhandle and extreme northwest South Plains where totals were near or just slightly above average for the two week period.
- The below map also shows how much rain has fallen across the south-central United States this year, through July 12th, 2010, as a percent of normal. The map also reflects that much of the western half of Texas, as well as South Texas, has recorded above normal to much above normal precipitation to this point. Many locations over the South and Rolling Plains are running 1.5 to 3 times that of normal through the first half of the year.