Drought conditions are improving in some areas of the Southwest US
February 22, 2019
With a sigh of at least some relief, ranchers and farmers in the southwest U.S. have gotten a break from the intense drought of 2018 through timely winter snow and rainfall, although climate experts announced during a live webinar Thursday, Feb. 14, it will still take time for long-term drought impacts to ease up.
This update regarding the drought that has gripped the southwest including Colorado, Arizona, New Mexico and Utah, was released by experts from the National Oceanic Atmospheric Administration's Climate Prediction Center, and also from Arizona State University, coinciding with the issuing of an El Nino Advisory.
"We're in an El Nino Advisory as of today (Feb. 14), which is a change from the El Nino Watch that has been in place since last summer. As we go into the spring, the skill in forecasting El Nino decreases. As the winter began, there was about an 80 percent chance of El Nino developing. Currently we now have a 55 percent confidence that it will persist through March/April/May 2019, and after that it becomes a toss-up," said Mike Halpert, deputy director of NOAA's Climate Prediction Center.
For the arid Southwest, El Niño is often crucial for bringing beneficial winter rains and snow, which play a critical role in helping to relieve or eliminate drought in the Southwest. El Niño is a natural climate pattern that occurs every three to five years, reflecting a periodic warming of the tropical central and eastern Pacific Ocean. It affects global weather patterns (winds, storms, temperature, precipitation). While El Nino typically develops in late summer or fall, and dissipates in spring, it is typically strongest in winter. Subsequently, the jetstream drops south into southern California and moves east across the U.S. and through the central Plains, producing more active winter weather in its path.
“We are just happier that this year has been a lot better than last year, but we hope to have improvement.”
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Meanwhile, the advisory now indicates a weak El Niño was present in January 2019 with above-average sea surface temperatures across most of the equatorial Pacific Ocean.
Since the drought in the Southwest was so entrenched, it still persists in many regions. "If you're in the D1 drought category and get decent rains, it can alleviate the drought," Halpert said. "When drought is more severe, even with good rains you still have some drought lingering, and that's the status for much of the Southwest."
That's because in spite of good snowfall in the region this winter, soils are very dry and reservoirs are low.
"It will require a lot of moisture over a long time to replenish the soil moisture sufficiently to create runoff that re-fills the reservoirs. And of course these low reservoir levels adds urgency to the Colorado River Drought Contingency Planning," said Elizabeth Weight of the NOAA/National Integrated Drought Information System in Boulder, Colo.
With the update to an El Nino Advisory now, this change has three basic requirements. "We had two of the three necessary conditions since October, that the east-central equatorial Pacific Ocean is one-half degree (0.5) Celsius warmer than normal, and that those conditions are expected to persist. It has been above the threshold for the past four months. But the critical part is, the warmer than normal ocean wasn't having an impact on the atmosphere above it, and that's what happened in January," Halpert said. "So, the thing we look for most, are changes in tropical rainfall across the Pacific Basin, which usually moves across the Pacific Ocean from the western into the central Pacific. But that's not the case with this one. The tropical rainfall was essentially stuck in the western Pacific, and only recently did it move into the central Pacific Ocean," Halpert said.
Actually, the southwest did better than they anticipated-back in November. In an eye-opening report issued last October, 25 percent of the southwest region was in the precarious categories of exceptional drought (a dark color on graphics,) and extreme drought (red).
"However, currently that area is just under 7 percent. So this is a big improvement," said Nancy J. Selover, Ph.D., Arizona state climatologist and co-chair and Drought Monitoring Technical Committee co-state coordinator, CoCoRaHS at Arizona State University in Tempe. Selover presented data with Halpert during the webinar.
"Also, Colorado Basin precipitation at the end of the last water year was at 70 percent less than what they normally get," Selover said. "In a much-improved outlook now, the Colorado Basin currently is 100 percent of average or better. There is some snowpack on these areas. We'll have to see what happens in spring."
The official spring three month outlook for March through May was released on Feb. 21. "This is something to pay attention (to) all forecasts will be updated," Halpert said.
Meanwhile, snow came and is starting to fall on top of dry soil largely in Utah, Colorado and New Mexico, which is beneficial, however when runoff season comes, much of that water will go directly into the soil, rather than going in streams and reservoirs as storage. "If it just goes directly into the soil, it's not where we can use it as a water resource. We want to get a lot of it instead into the reservoirs, to provide water to cities and towns and for irrigation," Selover said adding, "If you have a low reservoir when you start with, it's tough to get it up to where you want it."
The recent moisture in the Southwest has been good in the short term, Selover said. "In the long-term, it's okay, but one year in itself isn't going to bring us up to normal. It takes a number of years to erase a deficit."
In other favorable news, the Southwest has had cooler than normal conditions since October. They've also experienced more snow than rain, which Selover noted is also good. "We're happy to see this, it's a welcome change from last year."
New Mexico is starting to get to their windy season and they have a lot of dry soil. So dust from the White Sands National Monument is, unfortunately, being transported all the way into Texas, creating a lot of particulates in the air with the dust storms.
Utah: has snowpack at or above average in most locations. But their soils have been dry under the snow. So there are still a few areas of drought, although a fair amount of improvement from Utah into southern California and Arizona. With an exceptional drought, it takes months and months to get to that point, and it often also takes months and months to ameliorate it.
Most significant drought is still in Colorado and New Mexico. By terminology, there are a few areas that are still exceptional to extreme.
In Colorado the winter wheat is in the ground, ski resorts are doing well, the Upper Rio Grande River Basin and the San Juan Basin are faring better than last year. The exposed soils are still wet, but soil underneath the snowpack is still dry.
Southern and western Colorado have seen improvement the past few months. Some areas are also forecast to see some rains and some further improvement in the rest of February going into March.
In New Mexico (northern New Mexico, parts of central and eastern New Mexico are similar to southern/western Colorado where some improvement the past few months with forecasted rains expected to improve conditions into March. However, San Juan County still has water restrictions. They're also having issues with their reservoirs, as they're starting out very low from last year and they have the dry soil under the snow.
Arizona is a little different. Arizona has done fairly well reducing drought. The Salt-Verde watershed has wet soil underneath the ground. It stayed wet until they received snowfall. Groundwater levels are low, so the recovery will be slow. But the runoff outlook into the reservoirs is good, at this time.
Meanwhile, regarding lettuce in southwest Arizona, with the rain, farmers have had delays getting out in the field.
In conclusion, Selover said, "We're just happier that this year has been a lot better than last year, but we hope to have improvement." ❖
— Hadachek is a freelance writer who lives on a farm with her husband in north central Kansas and is also a meteorologist and storm chaser. She can be reached at email@example.com.