outlook+water: Drought slightly decreases but expected to persist and expand, El Niño fading, and active hurricane season predicted

SUMMARY:

• Drought conditions declined to 26% of the state (D1–D4); statewide reservoir storage rose to 77.5% full but still about seven percentage points below normal for this time of year.
• La Nada has an ~80% chance of arriving in April-May-June, with a 70% chance of La Niña 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 May 31, 2024.

Several interesting things are happening these days, including recent rains in Central Texas and projections for the 2024 hurricane season.

Recent rains in Central Texas! (but not all benefit)

Yay! Rains and rises in (one) reservoir! Lake Buchanan rose from about 47% full a month ago to 76% full today, adding more than 200,000 acre-feet of storage to the reservoir (Figure 1a). I haven’t heard anything official, but this surely will hold off any reduced allocations from the Highland Lakes this year. Lake Travis, however, saw little improvement, rising from 37% full a month ago to 40% full now (Figure 1b). Canyon Lake has continued to decline, from 59% a month ago to 58% today (Figure 1c), as did Medina Lake, declining from 2.8% to 2.5% full over the last month.

Figure 1a: Reservoir storage for Lake Buchanan (graph from Texas Water Development Board).

The Hurricane Season Expected to Be Busy

NOAA is predicting an above-normal hurricane season. Sea-surface temperatures in the mid-Atlantic are already roaring hot and exceeding last year’s records (Figure 1d). Accordingly, NOAA is projecting an 85% chance of an above-normal season, which stretches from June 1 through November 30. They are forecasting 17 to 25 named storms (winds of 39 mph or higher), eight to 13 hurricanes (winds of 74 mph or higher), and four to seven major hurricanes (Cats 3, 4, or 5 with winds of 111 mph or higher). Warmer temps and a lack of El Niño shearing winds indicate an active season. NOAA also announced names for the 2024 season, including Beryl, Leslie, and Raphael (Figure 1e). NOAA will update its forecast in early August.

Last year, NOAA projected 12 to 17 named storms, five to nine hurricanes, and one to four major hurricanes for a year that ended with 20 named storms, seven hurricanes, and three major hurricanes, so not bad. Of the named storms, one hit Texas, three hit the United States, and eight made landfall.

Note: NOAA has discontinued the previous viewer I used to generate the plots I usually show here. Unfortunately, the new viewer has less functionality (I can no longer access 90-day precipitation summaries, a good indicator of drought) and lower graphic quality (I can no longer export graphics; I have to screen capture). The new viewer focuses on stream flows and floods rather than precipitation and drought. ☹

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 major downpours (more than 20 inches) in the southeast caused flooding along the San Jacinto River (Figure 2a). The percent-of-normal rainfall over the last month resembles the rainfall map (Figure 2b). Where it’s raining, we’re getting much more than normal; where it is not, we’re getting much less (Figure 2b).

The amount of the state under drought conditions (D1–D4) decreased from 27% four weeks ago to 26% today (Figure 3a), with drought improvements focused in the northern part of the Hill Country and drought development in various places across the state (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, 49% of the state is abnormally dry or worse (D0–D4; Figure 3a), up from 47% 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 is in drought north of Elephant Butte Reservoir (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—rose slightly from 22.0% four weeks ago to 23.4% more recently (Figure 4c), slightly below median storage since 1990.

Combined conservation storage in the Amistad and Falcon reservoirs decreased to 18.9% full from 19.9% 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 (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 77.5% full, up about 760,000 acre-feet from 75.1% 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 70% 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 was not able to 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 Buchanan due to its quick rise out of near record-low territory over the last month, although it continues to be almost 20 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 remain in El Niño conditions; however, temperatures are dropping, although more slowly than anticipated (Figure 6a). Projections suggest El Niño conditions continue with a return to neutral conditions in the April-May-June season, a month later than earlier projections. Outside of the month’s delay in neutral conditions, this month’s projection is similar to last month’s except for a cooler La Niña (Figure 6a; these end-of-projection bumps appear to be due to uncertainty).

The official probabilities, a month newer than the projections in the graph, still give La Nada conditions a ~80% chance of arriving in April-May-June, a coin toss for La Niña conditions arriving June-July-August with a 70% chance for La Niña conditions arriving July-August-September (Figure 6b). Accordingly, we remain under an El Niño Advisory and 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 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).