For portions of Grayson County, August 2017 is the wettest August on record and the wettest in more than a century, the National Weather Service said Wednesday. Over the past month, parts of the region have seen nearly five times the normal rainfall for the month, with less than a week still to go.
NWS Meteorologist Lamont Bain said a co-op station in Sherman has recorded 11.99 inches of rainfall for the month as of Wednesday, putting it behind 1915 as the wettest August on record. However, storms on Thursday brought an additional 1.5 inches of rain, making this August the wettest on record with a total rainfall of 13.49 inches.
On average, the same weather station would normally see about 2.56 inches of rainfall for the entire month.
“We’ve had a very wet summer in North Texas,” Bain said, noting that a high-pressure ridge that normally keeps the region dry has been unstable this year. “Without that suppression, it has opened up the doors for more rainfall in the region.”
Bain said the region last saw rain to this level when 12.39 inches of rain fell in August 1915. Bain noted the weather service is missing data from 1898 to 1901.
A second weather station at North Texas Regional Airport had recorded 10.12 inches of rainfall this month through Wednesday. However, Bain noted that data at the site only dates back to 2009, making it less complete and comprehensive.
The update comes as portions of the region saw more than 2.88 inches of rain within the past five days. This includes 1.38 inches of rain that fell early Wednesday morning and an additional 0.25 inches of rain late Tuesday afternoon.
“It started raining just after 2 a.m. and when it was all said and done we had 1.38 inches of rainfall,” Bain said of Wednesday’s storms.
On Aug. 13, portions of Grayson County received just under nine inches of rain during overnight storms that flooded many low lying areas and developments along creeks and tributaries. A second storm system on Aug. 16 brought an additional four inches of rain to portions of the county.
Texas State Climatologist John Neilsen-Gammon said the recent weather represents a trend of late summers and early falls being wetter than the historic average. Neilsen-Gammon attributed the unseasonable weather to stalled systems in the area that have displaced a high-pressure ridge that typically leaves the region dry and warm throughout the summer.
While the state has received about the same amount of rain it normally does for this time of year, Neilsen-Gammon said it has mostly been concentrated in North Texas. Hurricane Harvey, which is expected to bring rainfall totals that will be measured in feet in the coming days will likely shift that balance.
With conditions typically dry, Gammon said the soil can typically take about four to five inches of rain before the rest is lost to runoff. This runoff then helps contribute to the levels and ultimate health of local reservoirs and streams, he said.
By Friday afternoon, the elevation of Lake Texoma stood at 617.86 feet, with 3.06 percent of the flood pool full. Any elevations above 616.86 feet enter into the lake’s flood pool, a portion of the lake dedicated to averting flooding situations.
Moving forward with the rest of August, Bain said the region’s weather patterns will start to return to normal.
Despite a 20 to 30 percent chance of rain remaining in the forecast for the weekend, Bain said they will likely be more scattered showers and will not have the same impact as previous storms.
In its weekly water update, which was released Monday, the Texas Water Development Board said only 1 percent of the state is currently in a state of drought. This is down from 4 percent a week ago and 6 percent three months ago.
“More rain = more improvement in drought conditions with drought now erased in the Panhandle,” Robert Mace, TWDB deputy executive water science and conservation administrator, said in the report. “Projections suggest a drought-free Texas by December, if not sooner.”