Mixed bag of expectations for precipitation from El Niño

US Drought Monitor August 21, 2018.

From The Colorado Springs Gazette (Liz Forster):

Last week, the National Oceanic and Atmospheric Administration predicted a 70 percent chance of an El Niño for the 2018-19 winter. Tom Di Liberto, a meteorologist with NOAA, said it’s too early to say with confidence the strength of the climate variation event.

“As we move into the fall, our models and the ocean-atmosphere conditions will be clearer and we can better determine how strong the El Niño will be,” he said. ”The stronger the El Niño, the more consistent with the general pattern of an El Niño this winter will be.”

[…]

Colorado straddles the jet stream as it runs across the northern and southern tiers of the United States, and scientists have not been able to find corollary data between El Niño events and the snow conditions in Colorado.

“In general, I don’t tend to make a whole lot out of El Niño predictions in terms of snow conditions in Colorado because we’re right in that inflection point,” Molotch said.

He continued, “You also have to remember that the Sierras, the mountains in the Pacific Northwest and others in the western Rockies are really efficient in squeezing snow out of these storm systems. By the time those storms get to Colorado, you don’t have a significant amount of snowfall.”

Even if Colorado’s winter definitively sways with the northern or southern jet stream, the characteristics ascribed to El Niño events are influenced by other climactic and weather elements that are unique to a specific winter season.

”We don’t necessarily see storms moving to the same places and in the same direction winter-to-winter in a normal year, which is also the case for an El Niño year,” Di Liberto said. “Every winter has other factors that can tweak the characteristics of a general El Niño.”

[…]

As Colorado awaits its uncertain snow season, the state is expected to remain in drought through the end of November with above-average temperaturesThe seasonal drought outlook for Aug. 16 through Nov. 30 produced by the Climate Prediction center forecast drought to persist but improve in the southern part of the state, but to persist without improvement in the central and northwest corner.

El Paso County — which currently is a mosaic of abnormally dry, moderate drought and severe drought — sits in the latter of the two predictions.

From The Albuquerque Journal (Maddy Hayden):

Recent rainfall has done little to assuage long-term drought conditions throughout New Mexico.

“We’re still seeing these long-term lingering effects,” National Weather Service senior hydrologist Royce Fontenot said Tuesday in conference call. “The very dry winter and spring have done a lot of damage to the environment.”

Some monitoring stations, Fontenot said, went more than 100 days without measurable precipitation since October, and “it really seemed like someone turned off the tap” to the start of the monsoon season, so they are still at a precipitation deficit.

The worst drought conditions in the country are centered over Colorado, Utah, Arizona and northwestern New Mexico, as well as north-central New Mexico, where precipitation levels are well below normal.

That area remains in exceptional drought.

Conditions have also worsened in the Roswell area, which is now in extreme drought.

The portion of the state in exceptional drought decreased from 15.68 percent last month to 14.54 percent.

Much of the rest of state has improved to severe and moderate drought conditions.

On Wednesday, the board of the Albuquerque Bernalillo County Water Utility Authority voted to lease 20,000 acre-feet of water from Abiquiu Reservoir to the U.S. Bureau of Reclamation for $2 million to keep the Rio Grande flowing through Albuquerque, largely for the protection of endangered species…

John Stomp, chief operating officer of the water authority, said that without rain and this intervention, the Rio Grande would likely have soon gone dry from the Bernalillo Bridge to Central Avenue.

Last week, the Middle Rio Grande Conservancy District announced it was expecting to run out of storage reserves by the end of this week.

By catching some of the 20,000 acre-feet that leaks from the Rio Grande into their drainage systems – and thanks to Wednesday’s rain – that day may now come on Sunday or Monday.

“We’re in the position now where every little bit helps and it should be a good thing for us,” said David Gensler, water operations manager for the district. “We’ve managed to kick the can down the road a little bit.”

One of the reservoirs the district uses for storage, El Vado, is at just 6 percent of capacity.

As storage runs out, farmers around the state have had to cut back on irrigation.

The lack of rainfall has curtailed grass and hay growth.

From The Summit Daily (Deepan Dutta):

El Niño can shift jet streams south, pushing cooler, wetter weather into Colorado’s backyard, whereas La Niña usually shifts the jetstream north and brings the opposite — hotter, drier weather — to the western U.S. La Niña was one of the reasons for the drought and wildfires across the west this summer…

Even in an El Niño year, other factors, such as local temperatures and the exact path of the jet stream that separates the cool and dry air, may be more important than the broader pattern occurring in the Pacific, and even a minor jetstream shift can change local day-to-day weather patterns.

From the New Mexico Political Report (Laura Paskus):

Earlier this week, the [Middle Rio Grande Conservancy District] had already announced it anticipated entering Prior and Paramount Operations—when it can only meet the irrigation needs of about 8,800 acres of pueblo lands, which have the most senior water rights in the valley.

That includes the pueblos of Kewa, Cochiti, San Felipe, Santa Ana, Sandia and Isleta. Because the pueblos were here long before any of the valley’s other communities, when Congress passed an act in 1928 supporting the irrigation district’s creation, it noted that the water rights to those pueblo lands are “prior and paramount to any rights of the district.”

The pueblos have worked with the irrigation district and federal water officials this year, according to MRGCD, managing Prior and Paramount waters to “support regular irrigation as long as possible, for the benefit of all irrigators.”

No quick end to Article VII

Poor snowpack and low runoff has also forced other water users on the Rio Grande to exhaust their supplies. As of Thursday, for example, Elephant Butte Reservoir is at just 5.5 percent of its capacity, holding just over 107,000 acre feet of water.

In May, New Mexico entered into Article VII restrictions when combined storage in Elephant Butte and Caballo reservoirs dropped below 400,000 acre feet. Under Article VII of the Rio Grande Compact, that means Colorado and New Mexico can’t store water in any upstream reservoirs built after 1929—including El Vado.

“We will anxiously watch the snowpack this winter in hopes that it will provide some relief for the next year,” said U.S. Bureau of Reclamation spokeswoman Mary Carlson. “If we exit Article VII restrictions at all next year, it likely won’t be until June at the earliest.”

She added that means storage in El Vado will be limited to Prior and Paramount water for pueblo lands and then relinquishment credit water for MRGCD until the combined storage in Elephant Butte and Caballo rises above 400,000 acre feet.

That will be a long climb, she said. Projections currently show Elephant Butte and Caballo will have about 75,000 acre feet at the end of this season.

“Of course we will gladly anticipate any forecast that calls for above average precipitation,” she said. “We will hope for the best, but manage our supplies cautiously as we are aware that forecasted precipitation, especially with above average temperatures, doesn’t always provide as much benefit as we’d like.”

[…]

El Niño conditions favor, but don’t guarantee, a wet winter for NM

During the monthly National Oceanic and Atmospheric Administration climate briefing on Thursday, climate and weather experts noted El Niño conditions have a 70 percent chance of developing in the fall, and they forecasted wetter-than-normal conditions in the southwestern United States for November, December and January.

“We’re more likely to have El Niño than not,” said Dan Collins, meteorologist and seasonal forecaster at NOAA’s Climate Prediction Center. But, he added, the predicted El Niño doesn’t look to be a strong one.

By tracking temperatures in the Pacific Ocean, scientists attempt to forecast what will happen across land surfaces. Typically, during El Niño conditions, the track of winter storms coming off the Pacific moves southward. For the swath of land from southern California eastward across the southern part of the U.S. to Florida, El Niño conditions can mean more winter storms. That is, it sets up the conditions for wetter weather but doesn’t guarantee them.

During Thursday’s climate briefing, Jake Crouch, a climate scientist with NOAA, pointed out that the contiguous United States had its 11th-warmest July on record—and there were record warm temperatures across much of the West, including in New Mexico.

The first seven months of the year were also warmer than normal. For the 25th consecutive year, Crouch said, January-to-July temperatures nationwide exceeded the 20th century mean. And New Mexico and Arizona experienced their warmest years to date in 124 years of record-keeping.

That warming trend will likely continue across the West through the fall, particularly in the Four Corners states.

“What El Niño tends to bring us is actually somewhat cooler temperatures, and so when we see a forecast of warmer-than-normal temperatures, that mostly reflects warming trends,” said David Gutzler, a climate scientist and professor in the Department of Earth and Planetary Sciences at the University of New Mexico. “But this year, that forecast is tempered somewhat by El Niño.”

Even as the climate continues its warming trend, there will be natural variability in weather patterns from year to year—swings between wet years and dry years. That’s different from changes in the climate, which relate to long-term averages.

NOAA also forecasted an improvement through the fall and winter in drought conditions across the Four Corners, including New Mexico and Arizona.

Gutzler said it’s worth being cautious about that, since drought outlooks are based on local precipitation and don’t take into account things like reservoir storage, which relies upon snowpack.

“I’ll be an optimist and say, [based on what we know] historically, if El Niño develops as projected and persists through the winter, the odds get shifted somewhat toward good snowpack conditions,” he said. But another important question for water managers—and users—is what happens at the end of winter and in early spring.

Warm winters, and early springs mean that snowpack melts too early and too quickly.

“I don’t think one wet winter solves all of our long-term water challenges, but I don’t want to dismiss how great it would be to get a really healthy snowpack,” he said. “We will root for a wet winter—I will, anyway.”

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