Heat hangs on: NWS sees more of the same through mid-August

The National Weather Service Brownsville-Rio Grande Valley station on Thursday released its outlook for July through September, predicting persistent above-average heat but also the return of rain to some degree, while the Gulf of Mexico remains a tropical “wild card” in months to come.

NWS Warning Coordination Meteorologist Barry Goldsmith said the best chances for above-average heat are July through at least mid-August. As expected, the wet and stormy weather pattern that was among the Valley’s top-five wettest periods for March through early June for the Valley “turned on a dime on June 9” with the arrival of a persistent, powerful “heat dome.”

The dome shows no signs of loosening its grip this week, though the forecast for early next week does include the possibility of rain.

Record hot temperatures were observed across the Valley June 9 to 27 (daytime and nighttime temperatures combined), Goldsmith reported, adding that the relentless heat wave means June 2023 probably will go down as one of the five hottest Junes on record.

Heat indexes, which combine actual temperature with relatively humidity to give a “feels-like” temperature, reached 111 degrees and higher in many parts of the Valley June 12 to 28, while McAllen’s heat index peaked at 116 or higher for 12 days in June, including 11 straight days from June 13 to 23, he said.

This June obliterated previous June records for consecutive days with heat indexes that high, Goldsmith said, noting that June 2019 saw just three straight days (four days total for McAllen in June 2019), with similar records from 1998 and 1980. This summer’s heat wave erased any moisture accumulated during the spring rains, he said.

“The record heat wave wiped out moisture gains from the … wettest spring period, then rapidly dried out most short grasses and some bush,” Goldsmith said. “The dryness also began to impact crops and livestock by month’s end.”

The potential for rapid wildfire growth as range land and brush have dried out is a growing source of concern, likely to remain so through at least mid-August “if ample rains don’t arrive,” he said.

Likewise, water levels at Falcon Reservoir fell steadily through June, from 24.4 percent of total capacity at the start of the heat wave to 20.4 percent as of Thursday due to targeted water releases and very high evaporation rates, Goldsmith said. Additional drops in water levels are likely into mid-August (normal for that time of year), with some relief possible in the form of rain the first two weeks of July, Goldsmith said.

The combined levels at Falcon and Amistad reservoirs could dip close to 25 percent, which in summer 2022 triggered stage-two water restrictions, Goldsmith noted. And while Valley residents are likely stuck with above-average heat at least through mid-August, late August through September are unpredictable in a tropical sense, he said.

“There is always uncertainty on tropical waves or tropical cyclones from the Gulf and eastern Pacific, typically by late September,” Goldsmith said. “The eastern tropical Pacific is expected to be more active than the Atlantic basin, overall, due to El Nino.”

El Nino, which has arrived and is getting stronger, suggests an average or below-average Atlantic hurricane season, though the Gulf can be unpredictable late August and September, he said.

“And the eastern Pacific, which should be more active, could provide welcome rains to the middle (and) lower Rio Grande basin later in September,” Goldsmith said.