Wet forecast a sign of El Niño’s growing influence on DFW’s weather

With the second storm system in a week on its way to North Texas, it appears that El Niño is living up to its preseason billing.

Last weekend’s rainfall brought a record flood to the Richland-Chambers reservoir and helped erase months of drought across North Texas.

Storms that will blow into the Dallas-Fort Worth area on Friday are expected to bring another 2 inches of rain on Friday and Saturday. Some low-lying areas could see flooding.

“It doesn’t look like this would set any high totals like last weekend but everyone is going to get a good amount of rain,” said Matt Bishop, a meteorologist with the National Weather Service in Fort Worth.

The good news is that the rain should be gone in time for trick-or-treaters on Saturday night.

Another heavy dose of storms, however, is setting up to blow through North Texas next week.

The onslaught of storms appears to be vintage El Niño, the weather phenomenon in which the Pacific Ocean sees warmer than normal surface temperatures off the coast of South America. That tends to funnel storm systems across the southern U.S.

“It looks like we’re going to be getting three storms in three weeks so we’re in that pattern for now,” said State Climatologist John Nielsen-Gammon. “This could be the start of the El Niño weather pattern we’ve all been waiting for.”

The Climate Prediction Center is continuing to predict a wet fall and winter across Texas in its long-range outlooks.

Nielsen-Gammon believes El Niño had a direct influence on last weekend’s record rainfall by helping intensify Hurricane Patricia, which funneled tropical moisture into Texas.

The latest El Niño advisory says there is a 95 percent it will continue through winter of 2015-2016.

The rainfall dramatically improved drought conditions across the state and also helped the winter wheat crop for farmers, Nielsen-Gammon said.

Last week, 21 percent of the state was exceptional or extreme drought, the two most serious categories. This week, those two categories of drought had been wiped off the statewide map.

‘A very rare event’

In last weekend’s storm, Navarro County was the bulls-eye where one rain gauge recorded 29.5 inches near Dawson and almost the entire county saw more than 20 inches of rainfall.

Much of that heavy rain funneled into Richland-Chambers, which is owned and operate by the Tarrant Regional Water District, and supplies water to Tarrant County. The lake and the neighboring wetlands comprise 55 percent of TRWD’s water supply.

At the height of last weekend’s flood, the lake was hit with flows two-and-a-half times greater than what’s seen at Niagara Falls.

During a 24-hour period, flood waters dumped the equivalent of three Eagle Mountain Lakes into Richland-Chambers and left enough water behind to fill Lake Benbrook, according to the TRWD.

“We have seen 552,000 acre feet flow into Richland, almost exactly half the volume of the reservoir,” Marshall said. “That is 180 billion gallons. That is three times the volume of Eagle Mountain.”

Two days into the flood, TRWD’s meteorologist estimated the event “was equal to 75 percent of the theoretical maximum 48-hour storm that could occur,” Marshall said.

“This was a very rare event,” Marshall said. “The storm totaled 26.8 inches at that point. The 500 year two-day storm is about 16 inches, based on a USGS study. So this event was very rare.”

‘We have no worries’

What it means for Tarrant County is an almost full water supply going into winter, meaning there are no concerns for drought restrictions. Eighty-six percent of of TRWD’s water supply comes from Richland-Chambers, the neighboring wetlands and Cedar Creek Lake.

Overall, TRWD’s water supply sits at 98 percent, compared with 63 percent a year ago.

“From a water supply standpoint, we have no worries this year,” Marshall said.

While there may be a few lingering showers Saturday morning, this latest round of rain should move out of North Texas by Saturday afternoon — in time for trick-or-treaters to hit the streets.

“It should be dry by evening,” Bishop said.

This story was originally published October 29, 2015 at 1:33 PM with the headline "Wet forecast a sign of El Niño’s growing influence on DFW’s weather."