Although some areas in western Washington still suffer from severe drought, climate experts say cooler-than-average highs in much of the Pacific Northwest have blunted the drought’s potential this summer, despite below-normal precipitation.
And while forecasts currently predict warmer-than-normal temperatures over the next three months, the recent disappearance of El Nino could help usher in a cooler fall and winter.
Those were among the conclusions of an Aug. 26 drought webinar presented by federal and state agencies participating in the Pacific Northwest Drought Early Warning System, which covers Washington, Oregon, Idaho and Montana.
Also discussed was a new browser-based weather tracking tool.
Jeremy Wolf, a meteorologist for the National Weather Service in Spokane, presented the climate outlook for the region. He noted that after several months under weak El Nino conditions, sea surface temperatures near the equator cooled over the past month, and neutral conditions—when sea surface temperatures are normal—have emerged.
“There’s still a chance that El Nino could resurge, or even that La Nina could emerge, but it seems more likely we’ll have ENSO-neutral conditions” through the fall and into winter, he said. For the Northwest, that’s more likely to bring cooler temperatures. Precipitation is more variable under ENSO-neutral conditions, he noted. ENSO stands for El Nino/Southern Oscillation, and refers to a cycle of variations in sea surface temperatures, convective rainfall, surface air pressure and atmospheric circulation that occurs across the equator in the Pacific Ocean.
Wolf cautioned, “Not every neutral year is alike,” so ENSO conditions do not predict with certainty whether an upcoming season will be wetter or drier, or warmer or cooler.
Of the 14 neutral winters since 1980, six have been cooler than normal in the Northwest, five have been normal, and three have been warmer than normal, he said. For precipitation in the Northwest during those neutral winters, five have been drier than normal, six have been normal, and three have been wetter than normal, he noted.
Over the next three months, Wolf said, the Climate Prediction Center forecasts temperatures in the Northwest will be warmer than normal, with equal chances of wetter or drier than normal conditions. He said the 40 percent chance of warmer than normal temperatures in September, October and November compared to the last 30 years is due largely to the region’s experience over the last 10 years of having warmer fall and winter weather.
This summer, severe drought impacts were largely averted, said Nick Bond, Washington's state climatologist.
Bond said that from March through July, the Pacific Northwest was generally drier than normal, with close to normal temperatures in most areas. And while maximum daily temperatures over the last 60 days were cooler than normal, minimum daily temperatures were warmer, he said. Compared with the 30-year average, July was 0.7 degrees Fahrenheit below normal, and precipitation was about 68 percent of normal—a deficit of about one-quarter inch of rain, Bond said. Some areas in Oregon and southern Idaho have experienced above normal precipitation, however.
While drought persists throughout western Washington, into western Oregon and across the far northern portions of Washington, Idaho and western Montana, drought impacts have been relatively minor, he said.
The August drought webinar also featured a presentation by Katherine Hegewisch, researcher at the University of Idaho, who with colleagues has developed a browser-based application tool to track drought and moisture across the continental U.S. The U.S. Water Watcher brings together many different drought metrics under a single application, and standardizes them so they use the same percentile ranges and color schemes.
Hegewisch noted several agencies in the U.S. track water surpluses and deficits using different metrics. Those include meteorological drought, which is reduced precipitation; hydrological drought, which is reduced water supply in lakes, streams and groundwater; agricultural and ecological drought, which is reduced water for crops and ecosystems; and snow drought, which is reduced snowpack.
The new tool set up a system to gather real-time drought information from different sources, including the Northwest Climate Toolbox, the National Resources Conservation Service, WaterWatch, Groundwater Watch and NOAA.
Water Watcher includes real-time and historical data on precipitation, potential and actual evapo-transpiration, streamflows, reservoir levels, groundwater levels, soil moisture and snow-water equivalent, which can be customized on four maps and then compared with the U.S. Drought Monitor map.
The maps can also be zoomed to show location-specific data. Comparisons can be made using prior dates to show a drought’s progression over time, or in relation to prior years.
Hegewisch said the goals of the new tool are to show different drought types and moisture measurements using consistent colors and percentage metrics for a specific location. The tool enables the user to see and understand the differences between this year and a truly severe drought year like 2015, she noted.