outlook+water: Little change in drought and reservoir conditions, bye-bye El Niño, drought expected to remain

SUMMARY:

• Drought conditions declined slightly to 25% of the state (D1–D4); statewide reservoir storage rose slightly to 77.6% full but is still about 7 percentage points below normal for this time of year.
• La Nada is here with a 65% chance of La Niña arriving in July-August-September.
• Drought is expected to remain and expand in the western half of the state, including most of the Hill Country.

I wrote this article on June 30, 2024.

Hurricane season officially started on June 1, and it’s already been an active one for the Gulf of Mexico. Tropical Storm Alberto started as a disturbance on June 12 and formed into a tropical storm on June 19 in the Bay of Campeche. On June 20, Alberto made landfall near Tampico, Tamaulipas. Although Alberto landed south of the border, his influence extended to the whole gulf, spiraling storms into the entire Texas coast. Although some models suggested rainfall amounts approaching 20 inches in Central and South Texas, much less was realized. Regardless, Falcon Reservoir saw a bump from 10% full to 13.5% full (hey, an improvement is an improvement!). The rest of our reservoirs didn’t seem to get anything. For example, Choke Canyon continued to choke.

On June 24, a tropical wave formed in the Atlantic and became Tropical Depression Three in the Bay of Campeche on June 30. It’s expected to become a tropical storm on July 1 and make landfall north of Veracruz. It may spin off rainfall that affects the Lower Rio Grande Valley.

Beryl was born as a tropical wave on June 25. By June 28, it was a tropical storm and became a Category 1 hurricane the next day. The day after that, Hurricane Beryl was roaring as a Category 4, the earliest Category 4 on record (since 1851). As I wrote this, Beryl was barreling toward the Yucatan and the Bay of Campeche and could strike the Mexican coast south of Texas or even Texas if it swings north.

There’s another disturbance low in the Atlantic that the National Hurricane Center gives a 40% chance of turning into a tropical storm (Figure 1).

If tropical systems were soccer balls, you gotta think that the offense has to get one into the box we call Texas at some point, right? And for the record, I hope for a mellow, tropical system to refill our reservoirs and karst-y aquifers, not a Destroyer of Worlds.

Figure 1: Atlantic tropical cyclones and disturbances (graph from the National Hurricane Center).

Over the past month, we’ve had the usual more rain in the east and northeast (with large areas receiving more than 8 inches of rain) and less rain in the west (less than a quarter of an inch, Figure 2a). The percent-of-normal rainfall over the last month shows South Texas, the Lower Rio Grande Valley, parts of the Panhandle, and Northeast Texas receiving greater-than-normal rainfall while the rest of the state fell behind (Figure 2b). Over the past 90 days, the percent of normal shows North and Northeast Texas sittin’ pretty, the Lower Rio Grande Valley and mid-High Plains show splotchy good, but the rest of the state is in deficit (Figure 2c). A sizable hunk of Far West Texas has received less than 25 percent of normal rainfall over the past three months (Figure 2c).

The amount of the state under drought conditions (D1–D4) decreased from 26% four weeks ago to 25% today (Figure 3a), with drought improvements in the High Plains and Central and South Texas (Figure 3b). Extreme drought, or worse, stayed the same as four weeks ago at 2% of the state, with exceptional drought remaining at 0% (Figure 3a). In all, 39% of the state is abnormally dry or worse (D0–D4; Figure 3a), down from 49% four weeks ago.

The North American Drought Monitor, which runs a month behind current conditions, shows drought in New Mexico, Southern Colorado, and Mexico, among other places (Figure 4a). The Rio Grande Basin north of Elephant Butte Reservoir is in long-term drought (Figure 4a). The Rio Conchos basin in Mexico, which confluences with the Rio Grande just above Presidio and hosts the largest tributary to the Lower Rio Grande, remains in extreme to exceptional drought (Figure 4a).

Conservation storage in Elephant Butte Reservoir—an important source of water for the El Paso area—decreased from 23.4% four weeks ago to 17.7% more recently (Figure 4c), about six percentage points below median storage.

Combined conservation storage in the Amistad and Falcon reservoirs increased to 19.2% full from 18.9% four weeks ago, almost 40 percentage points below normal for this time of year (since 1990) and the lowest in at least the past 33 years for this time of year (Figure 4d).

Basins across the state continue to host flows over the past week below historical 25^th, 10^th, and 5^th percentiles (Figure 5a). Statewide reservoir storage is at 77.6% full, up about 31,000 acre-feet from 77.5% four weeks ago and about seven percentage points below normal for this time of year since 1990 (Figure 5b). Recent rains have not topped up most of the reservoirs in the central part of the state, although Lake Buchanan is now more than 77% full (Figure 5c).

The reservoir marked in orange in the Dallas-Fort Worth area (the lemon in a sea of blueberries) is New Terrell City Lake and has dropped from full in early March (Figure 5c). I could not discern the cause, but I suspect it is for maintenance on the reservoir and/or dam.

My (drumroll please) “Hydrograph of the Month” is Lake Arrowhead due to its quick rise from 55% full to 76% full over the last two months, although it continues to be about five percentage points lower than normal (Figure 5d).

Sea-surface temperatures in the Central Pacific that, in part, define the status of the weather phenomenon known as the El Niño Southern Oscillation are under neutral conditions, and sea-surface temperatures continue to drop, although more slowly than anticipated (Figure 6a). Projections suggest a transition to La Niña conditions in mid-to-late summer (Figure 6a, b). This month’s projection is similar to last month’s except for a cooler La Niña (Figure 6a; these end-of-projection bumps seem to be due to uncertainty).

The official probabilities, a month newer than the projections in the graph, still give La Nada conditions a ~65% chance of arriving July-August-September, rising to an 85% chance by October-November-December (Figure 6b). Accordingly, we are under a La Niña Watch.

The U.S. Seasonal Drought Outlook through August projects drought persistence and development in West and Far West Texas, with drought remaining (and expanding) in the Hill Country (Figure 7a).

The three-month temperature outlook projects above-average temperatures for the state (Figure 7b), while the three-month precipitation outlook favors drier-than-normal conditions for West and Far West Texas and wetter-than-normal conditions for the east (Figure 7c).